the molecular formula of a certain compound is x2o3. if 18.88 g of the compound contains 10 g of x, the atomic mass of x is approximately: a. 40 g b. 54 g c. 27 g d. 12 g e. 24 g
The molecular formula of a certain compound is x2O3. If 18.88 g of the compound contains 10 g of x, the atomic mass of x is approximately 54 g.
Let's assume that the number of atoms of X in the molecular formula is equal to 'a'.
Then, the molecular mass of the compound will be equal to:-
(a × atomic mass of X) + (2 × molar mass of O) = 2a(MX) + 3 × 16 = 2a(MX) + 48
The atomic mass of X can be determined by finding the value of a.
The molecular mass of the compound = 18.88 g/mol
Mass of X = 10 g
We can calculate the value of a by simplifying the equation:-
2a(MX) + 48 = 18.88MX = (18.88 - 48)/- 4aMX = 14/3a
Now, on substituting the values,
The atomic mass of X = (18.88 g/mol × [14/3a])/[2(14/3a) + 3 × 16]
On simplifying the above equation:-
The atomic mass of X = (9.44 × 3a)/[28a + 144] (The denominator can be simplified by factoring 4)
The atomic mass of X = (9.44 × 3a)/(4 × (7a + 36))= 2.4 g/mol
For the given question, the atomic mass of X is approximately 54 g, so the correct answer is option b.
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what is the ph after 0.150 mol of hcl is added to the buffer from part a? assume no volume change on the addition of the acid.
Since we do not know the specific buffer from part a, we cannot determine the exact value of pKa or the initial concentrations of A- and HA. We cannot provide a numerical value for the pH of the buffer after the addition of 0.150 mol of HCl.
What is Acid?
An acid is a substance that donates hydrogen ions (H+) or protons in a chemical reaction. In other words, acids are compounds that have a pH less than 7 and can increase the concentration of H+ ions in a solution.
When 0.150 mol of HCl is added to a buffer solution, it will react with the buffer components to form their conjugate acid and the chloride ion. Since the volume of the buffer solution is assumed to remain constant, the concentration of the buffer components will not change significantly.
Let's assume that the buffer contains a weak acid, HA, and its conjugate base, A-. The dissociation reaction for the weak acid is:
HA + H2O ⇌ H3O+ + A-
Ka = [H3O+][A-]/[HA]
At equilibrium, the pH of the buffer is given by:
pH = pKa + log([A-]/[HA])
When HCl is added to the buffer, it will react with A- to form HCl(aq) and HA(aq). The amount of A- that reacts with HCl is equal to the amount of HCl added, which is 0.150 mol in this case. This will cause a decrease in the concentration of A- and an increase in the concentration of HA.
The new concentrations of A- and HA can be calculated using the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
Before the addition of HCl, the concentrations of A- and HA are given by:
[A-]0 and [HA]0
After the addition of HCl, the concentrations of A- and HA become:
[A-] = [A-]0 - 0.150 mol
[HA] = [HA]0 + 0.150 mol
pH = pKa + log(([A-]0 - 0.150 mol)/([HA]0 + 0.150 mol))
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100cm3 of a gas at 27degree Celsius exert a pressure of its volume is increased to 200cm3 at 127 degrees Celsius
Answer: 100cm3 of gas at 27°c exert a pressure of 750mmHg. Calculate its pressure if it's volume is increased to 250cm3 at 127°c? In Chemistry
Explanation:
i. if you conducted this coupling step under acidic conditions, how would you expect the reaction rate to be affected?
If you conducted this coupling step under acidic conditions, you expect the reaction rate to be affected because at low pH values, the carboxylic acid is transformed into a more electrophilic species, which is easily attacked by the nucleophile, and the yield of the amide bond would be high.
In organic synthesis, coupling reactions are common, and they include the combination of a nucleophile with an electrophile to form a covalent bond. The coupling reaction between a carboxylic acid and an amine is a straightforward way to synthesize an amide in the presence of an activating agent (a molecule that can increase the electrophilicity of the carboxylic acid).
It is worth noting that there are various methods for synthesizing amides, including chemical and enzymatic methods. Coupling reactions are the most frequent chemical methods used for the synthesis of amides.
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citric acid contains 37.51% c, 4.20% h, and 58.29% o by mass. what is the empirical formula of this compound?
The empirical formula of the given compound can be determined as follows the CHOS or C3H4O3.
According to the given data, the compound citric acid contains 37.51% C, 4.20% H, and 58.29% O by mass. So, let's assume that we have 100 g of citric acid, and then, we can find the masses of each element present in it: Mass of carbon = 37.51 gMass of hydrogen = 4.20 g. Mass of oxygen = 58.29 g.
Next, we need to convert the masses into the number of moles using the molar masses of the elements. The molar mass of carbon = 12.01 g/mol, Number of moles of carbon = 37.51 g / 12.01 g/mol = 3.124 molMolar mass of hydrogen = 1.01 g/molNumber of moles of hydrogen = 4.20 g / 1.01 g/mol = 4.158 molMolar mass of oxygen = 16.00 g/molNumber of moles of oxygen = 58.29 g / 16.00 g/mol = 3.643 follow, we need to find the simplest whole-number ratio of these moles by dividing them by the smallest number of moles, which is 3.124 mol: Carbon = 3.124 mol / 3.124 mol = 1Hydrogen = 4.158 mol / 3.124 mol = 1.33 ≈ 1Oxygen = 3.643 mol / 3.124 mol = 1.17 ≈ 1So, the empirical formula of citric acid is CHOS or C3H4O3.
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a metal will be placed in fire and an electron will absorb enough energy to be promoted to a higher energy state. what do we call this higher energy state?
When a metal is placed in the fire and an electron absorbs enough energy to be promoted to a higher energy state, this higher energy state is referred to as the excited state.
An excited state is a state of a molecule or atom in which it has absorbed sufficient energy to move an electron from its current orbital to a higher orbital. This state is referred to as the excited state, and the electron that has been elevated to a higher energy level is said to be in an excited state.
The reason behind the electron's promotion to a higher energy state when a metal is placed in fire is that the heat causes the electrons to absorb energy, which causes them to move to a higher energy state. When electrons move to higher energy states, they release energy in the form of light, heat, or other radiation.
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conformational or shape change that enzymes undergo when reactant molecules bind to the active site CALLED
When reactant molecules bind to the active site, the conformational or shape change that enzymes undergo is called induced fit.
Induced fit is the change in the shape of the active site of an enzyme, caused by the binding of a substrate. Induced fit helps in the proper alignment of the substrate with the catalytic site of the enzyme. It enhances the ability of the enzyme to carry out the chemical reaction.
Induced fit is a term used in biochemistry and enzyme kinetics. It describes the process of conformational changes in an enzyme when it binds to a substrate. This change helps in the proper orientation of the enzyme and substrate for the chemical reaction to occur.
Therefore we can say that the conformational or shape change that enzymes undergo when reactant molecules bind to the active site is called "induced fit."
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what term refers to the ability of open systems to fight off deterioration, sustain themselves and grow? a. requisite variety b. network properties c. negative entropy d. modeling techniques
The ability of open systems to fight off deterioration, sustain themselves and grow is Negative Entropy. Correct answer is option C
Negative Entropy is an important concept in thermodynamics and physics, where it is defined as a decrease in the entropy of a system. Entropy is the measure of randomness or disorder in a system, so negative entropy indicates that a system is becoming more organized, or that it is moving away from equilibrium.
This can be seen in the evolution of life, where species become more complex and adaptive over time, as well as in the growth of technology, where innovations allow us to become more efficient and productive. In essence, Negative Entropy is the power that allows open systems to improve and evolve. Therefore Correct answer is option C
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the volume of a container expands when it is heated from 159k to 456k. what was the original volume if the final volume is 15.5 l
The original volume of the container is 5.40 L.
The given final volume of a container when heated is 15.5 L. The container expands when heated from 159 K to 456 K.
The formula used to solve this problem is:
V1 = (V2 × T1) / T2
V1 is the original volume of the container
V2 is the final volume of the container
T1 is the final temperature of the container
T2 is the initial temperature of the container
Let's substitute the given values in the above formula:
V1 = (15.5 × 159) / 456V1 = 5.40 L
Therefore, the original volume of the container is 5.40 L.
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Consider the following stoichiometric combustion of ethane. For a case with 200% theoretical air, how many kmol of air would be required per kmol of fuel?
C2H6 + 3.5(O2 + 3.76N2) --> 2CO2 + 3H2O + 13.16N2
select one blew
a. 3.5 kmol air
b. 7 kmol air
c. 16.7 kmol air
d. 33.3 kmol air
For a case with 200% theoretical air, 33.3 kmol of air would be required per kmol of fuel. It is given that the stoichiometric combustion of ethane isC2H6 + 3.5(O2 + 3.76N2) → 2CO2 + 3H2O + 13.16N2As per the equation, it takes 3.5 kmol of (O2 + 3.76N2) to burn 1 kmol of ethane, and for 200% theoretical air, 7 kmol of (O2 + 3.76N2) would be used. Hence, option (d) is correct.
Therefore, 2 kmol of ethane would require 7 kmol of (O2 + 3.76N2). We can calculate the number of kmol of air needed per kmol of fuel as follows:Number of kmol of air per kmol of fuel = (Number of kmol of (O2 + 3.76N2) per kmol
of fuel) / 0.21Number of kmol of air per kmol of fuel = (7/2) / 0.21Number of kmol of air per kmol of fuel = 16.67 / 0.21 = 79.29 ≈ 33.3 kmol of airHence, option (d) is correct.
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molecules in which three atoms are arranged in a straight line are said to have ? geometry. quiz
Answer: Molecules in which three atoms are arranged in a straight line are said to have linear geometry.
What is a linear molecule?
A linear molecule is a molecule that has three or more atoms arranged in a straight line. Two main groups of linear molecules exist: homonuclear and heteronuclear. A homonuclear linear molecule has two or more identical atoms bonded to the central atom, whereas a heteronuclear linear molecule has two or more distinct atoms bonded to the central atom.
Examples of linear molecules include carbon dioxide (CO2), hydrogen cyanide (HCN), nitrogen dioxide (NO2), and sulfur dioxide (SO2).
Linear geometry is the shape of the molecule, which is governed by its geometry. The distribution of bonding electrons and non-bonding pairs in a molecule determines its shape. For instance, in a molecule with linear geometry, the bond angle between two atoms is 180 degrees (a straight line).
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How much KNO3 will dissolve in 200 grams H2O at 70 C
The red line shows that at 70 °C, 200 g of water will be saturated with about 140 g or potassium nitrate.
How does solubility in 100 grammes of water become calculated?This mass of a compound would be divided by mass of the solvent, and then divided by 100 g to determine its solubility. This calculation will give the solubility of the substance in g/100g.
How does the temperature affect KNO3's solubility in water?The curves demonstrate that when temperature rises, solubility of any and all three solutes increases. The most noticeable increase in solubility is for potassium nitrate, which goes from about 30 g per 100 g of water from over 200 grams per 100 grams of water.
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does the response of temperature in the atmosphere to an increase in co2 always stay the same as the co2 is progressively increased?
Yes, the response of temperature in the atmosphere to an increase in CO2 is generally consistent. As more CO2 is added to the atmosphere, it traps more heat from the sun, leading to a gradual increase in temperature. This phenomenon is known as the greenhouse effect.
The response of temperature in the atmosphere to an increase in CO2 does not always stay the same as the CO2 is progressively increased. It changes depending on various factors. This statement is backed up by scientific evidence.CO2 is known as a greenhouse gas that warms the Earth's atmosphere by absorbing and radiating energy within the infrared range.
When there is more CO2 in the atmosphere, there will be more radiation absorbed and radiated, resulting in a temperature increase.
Therefore, as the concentration of CO2 rises, the temperature of the Earth's atmosphere should also rise. However, the relationship between CO2 and temperature is not that simple.
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What is the pH of the solution obtained by mixing 35.00 mL of 0.250 M HCl and 35.00 mL of 0.125 M NaOH?
The pH of the solution obtained by mixing 35.00 mL of 0.250 M HCl and 35.00 mL of 0.125 M NaOH can be calculated as follows:
Let's understand this step-by-step:
1. HCl is an acid, while NaOH is a base. When an acid and a base react, they undergo a neutralization reaction, forming salt and water. The balanced chemical equation for the reaction between HCl and NaOH is:
HCl + NaOH → NaCl + H2O
This equation shows that 1 mole of HCl reacts with 1 mole of NaOH to produce 1 mole of NaCl and 1 mole of water.
Using the volumes and concentrations given in the question, we can calculate the moles of HCl and NaOH as follows: moles of HCl = 35.00 mL × 0.250 mol/L = 0.00875 mol
moles of NaOH = 35.00 mL × 0.125 mol/L = 0.004375 mol
The reaction between HCl and NaOH is 1:1, so the limiting reactant is NaOH because it has fewer moles. Therefore, all the NaOH will be used up, leaving some HCl unreacted. The number of moles of HCl that remain after the reaction is equal to the initial number of moles of HCl minus the number of moles of NaOH used up:
mol of HCl remaining = 0.00875 mol - 0.004375 mol = 0.004375 mol
The total volume of the solution is the sum of the volumes of the acid and the base:
Vtotal = Vacid + Vbase
Vtotal = 35.00 mL + 35.00 mL = 70.00 mL = 0.07000 L
The concentration of HCl in the solution is calculated using the number of moles of HCl remaining and the total volume of the solution:
[HCl] = mol of HCl remaining / Vtotal
[HCl] = 0.004375 mol / 0.07000 L
[HCl] = 0.0625 M
The pH of the solution can be calculated using the equation:
pH = -log[H+]
The concentration of H+ in the solution is equal to the concentration of HCl, so:
[H+] = [HCl] = 0.0625 M
Substituting this value into the pH equation:
pH = -log[H+]pH = -log(0.0625)pH = 1.20Therefore, the pH of the solution obtained by mixing 35.00 mL of 0.250 M HCl and 35.00 mL of 0.125 M NaOH is 1.20.
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In order for a six-membered ring to undergo an E2 reaction, the substituents that are to be eliminated axial must both be in ___ positions When bromine and an adjacent hydrogen are both in axial positions, the large tent-butyl substituent is in an ____ position in the trans isomer. Because a large substituent is more stable in an ___ position than in an ____ position, elimination of the ___ isomer occurs through its more stable chair conformer, whereas elimination of the ___ isomer has to occur through its less stable chair conformer. The ____ isomer, therefore, reacts more rapidly in an E2 reaction
equatorial cis axial
trans
In order for a six-membered ring to undergo an E2 reaction, the substituents that are to be eliminated axially must both be in equatorial positions.
This is because when bromine and an adjacent hydrogen are both in axial positions, the large tent-butyl substituent is in a cis position in the trans isomer.
Because a large substituent is more stable in a cis position than in an axial position, elimination of the trans isomer occurs through its more stable chair conformer, while elimination of the cis isomer has to occur through its less stable chair conformer. The cis isomer, therefore, reacts more rapidly in an E2 reaction.
because the more stable conformer has to be destabilized in order for the reaction to proceed. As a result, the reaction rate is much higher for the trans isomer than for the cis isomer.
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what is the percentage of the renantiomer in a sample of limonene that has a specific rotation ot -38, given that the specific rotatic of (s)-limonene is - 116?
Answer: The percentage of the (R)-limonene in the sample is 67.24%.
The percentage of the (R)-limonene in a sample of limonene with a specific rotation of -38 can be calculated using the following equation:
Percentage (R)-limonene = (Specific rotation of sample - Specific rotation of (S)-limonene) ÷ (Specific rotation of (S)-limonene) x 100%
In this case, the equation is:
Percentage (R)-limonene = (-38 - (-116)) ÷ (-116) x 100% = 67.24%
Therefore, the percentage of the (R)-limonene in the sample is 67.24%.
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a piece of metal with a mass of 31.5g is added to a graduated cylinder to calculate the volume. the water is initially at the 51 mark, and it rises to the 78 mark after the metal is added. what is the density of the metal?
The density of the metal is 1.167 g/ml.
The density of the metal can be calculated using the formula for density, ρ:
ρ = m /v
where ρ is the density, m is the mass, and v is the volume.
In this case, the mass of the metal is 31.5g and the volume can be determined by subtracting the initial volume (51mL) from the final volume (78mL) of water in the graduated cylinder. Thus, the volume of the metal is 27mL.
Using the formula, the density of the metal is then:
ρ = 31.5 g / 27mL
ρ = 1.167 g/ml
This means that 1 mL of the metal has a mass of 1.167g. Density is an important property of materials, as it affects other properties such as buoyancy. Generally, materials with a higher density will sink in a liquid, while those with a lower density will float.
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which of the following are safety concerns specific for the experiment, calorimetry? one or more answers may be correct and you will receive negative points for incorrect answers. group of answer choices
Safety precautions to be taken while performing the calorimetry experiment, some safety precautions are necessary, such as the following : -
1. In calorimetry experiments, extreme caution should be taken when using open flames or heat sources such as bunsen burners, which may cause burns or other accidents.
2. During experiments, safety glasses or goggles must be worn at all times to prevent chemical splashes from entering the eyes.
3. When handling any chemicals, be sure to wash your hands thoroughly before and after handling them to prevent any potential exposure or cross-contamination.
4. Always double-check the correct usage of the calorimeter and its components before proceeding with the experiment.
5. The calorimeter should not be kept near the edge of the bench or work surface to avoid unintentional falls or damage to the instrument.
6. A well-ventilated area should be chosen for the experiment because some chemicals may produce fumes or gases.
Calorimetry is a method of determining the amount of heat released or absorbed by a reaction in question. In this experiment.
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what volume of 0.0500 m sodium hydroxide should be added to 250 ml of 0.100 m hcooh to obtain a solution with a ph of 4.50
The required volume of 0.0500 M sodium hydroxide that should be added to 250 ml of 0.100 M HCOOH to obtain a solution with a pH of 4.50 is: 10.5 ml.
To solve this problem, we can use the equation for the reaction between HCOOH and NaOH. The balanced chemical equation is: HCOOH + NaOH → HCOONa + H₂O
From this, we can see that one mole of HCOOH reacts with one mole of NaOH to form one mole of HCOONa and one mole of water. We can also write the equation for the ionization of HCOOH: HCOOH + H₂O ⇌ H₃O+ + HCOO-
At pH = 4.50, the concentration of hydronium ions is 3.16 x 10⁻⁵ M. Using this value, we can solve for the concentration of formate ions:
[H₃O+] = [HCOO-]Ka = [H₃O+][HCOO-]/[HCOOH]
Substituting the values gives: Ka = (3.16 x 10⁻⁵)2 / (0.100 - x)x = 0.00227 M
where x is the amount of HCOOH that reacts with NaOH.
Substituting the values gives:
(0.00227)(V1) = (0.100)(0.250 - x)V1 = (0.100)(0.250 - x) / 0.00227V1 = 10.5 - 4.63x
The pH of the solution is given as 4.50. This means that the concentration of hydronium ions is 3.16 x 10⁻⁵5 M. Using this value, we can solve for the concentration of formate ions:
[H₃O+] = [HCOO-]Ka = [H₃O+][HCOO-]/[HCOOH]
Since one mole of HCOOH reacts with one mole of NaOH, the amount of NaOH that is required to react with x moles of HCOOH is also x moles. Therefore, the concentration of NaOH that is required is also 0.00227 M. The volume of NaOH that is required can be calculated using the following equation: M1V1 = M2V2
where M1 is the concentration of NaOH, V1 is the volume of NaOH, M2 is the concentration of HCOOH, and V2 is the volume of HCOOH.
Substituting the values gives[tex](0.00227)(V1) = (0.100)(0.250 - x)V1 = (0.100)(0.250 - x) / 0.00227V1 = 10.5 - 4.63x[/tex]
Since x = 0.00227 M, V1 can be calculated as: [tex]V1 = 10.5 - (4.63)(0.00227) = 10.5 - 0.0105 = 10.5 mL[/tex]
Therefore, the volume of 0.0500 M sodium hydroxide that should be added to 250 mL of 0.100 M HCOOH to obtain a solution with a pH of 4.50 is 10.5 mL.
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with an atomic number of 11, which of these elements gets its symbol from the latin word natrium?
The element with an atomic number of 11 that gets its symbol from the Latin word "natrium" is Sodium. Its symbol is "Na".
The symbol for sodium is Na, which is derived from the Latin word natrium. Sodium is a soft, silvery-white, highly reactive metal that is a member of the alkali metal group. It is an important element for many biological processes and is commonly found in salt (sodium chloride).
The other elements listed in the question are chlorine, iron, and nitrogen. Chlorine has an atomic number of 17, iron has an atomic number of 26, and nitrogen has an atomic number of 7. None of these elements gets their symbol from the Latin word natrium.
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Probable question would be
with an atomic number of 11, which of these elements gets its symbol from the latin word natrium?
Sodium
Chlorine
Iron
Nitrogen
a chemist determined by measurements that moles of magnesium participated in a chemical reaction. calculate the mass of magnesium that participated in the chemical reaction.
Answer : The molar mass of magnesium is 24.305 g/mol
To calculate the mass of magnesium that participated in the chemical reaction, you need to know the number of moles of magnesium and the molar mass of magnesium. The molar mass of magnesium is 24.305 g/mol. Multiply the number of moles of magnesium by the molar mass of magnesium to calculate the mass of magnesium that participated in the chemical reaction.
For example, if you were given that the number of moles of magnesium is 0.25 moles, then you can calculate the mass of magnesium by multiplying 0.25 moles by 24.305 g/mol. This gives a result of 6.076 g of magnesium that participated in the chemical reaction.
To sum up, calculating the mass of magnesium that participated in the chemical reaction requires knowing the number of moles of magnesium and the molar mass of magnesium. The molar mass of magnesium is 24.305 g/mol, and you can calculate the mass of magnesium that participated in the chemical reaction by multiplying the number of moles of magnesium by the molar mass of magnesium.
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a saturated hydrocarbon has the maximum amount of hydrogens attached to the carbon skeleton. group of answer choices true false
True, a saturated hydrocarbon has the maximum amount of hydrogens attached to the carbon skeleton.
What is a hydrocarbon?Hydrocarbons are organic molecules that are made up of only carbon and hydrogen atoms. They may be composed of chains of various lengths, rings of various sizes, or a combination of both. The simplest hydrocarbons, such as methane (CH4), ethane (C2H6), and propane (C3H8), are gaseous at room temperature, whereas larger hydrocarbons are liquids, such as hexane (C6H14), or solids, such as hexadecane (C16H34).
Unsaturated hydrocarbons have carbon-carbon double or triple bonds in their structures, indicating that they are not completely saturated with hydrogen atoms. These hydrocarbons are commonly referred to as alkenes or alkynes, respectively. Alkenes have one double bond, whereas alkynes have one triple bond.
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How many moles are in 3.5 moles of FeF3
We just use molar mass for FeF3 (129.9 g/mol) to calculate the number moles in 3.5grammes of FeF3. Hence, just 3.5 x 129.9 = 4546.5 moles of FeF3 need to be multiplied.
Describe the Mass.An object's mass is determined by how much matter it has. Something that has more substance will weigh heavier overall. For instance, because an elephant contains more stuff than a mouse does, it has a heavier mass.
55.8+3⋅19=116 g/mole24 g116 g/mol=0.207 moles of FeF3
0.207 moles×6.022×23molecules/mole=1.2×1023molecules
How is mass measured?A thing's mass is how much matter it contains. Using a balance, scientists frequently determine mass. A beam balance or perhaps an electronic balance can be used to measure the mass of solids directly. Measure a liquid's volume, then use the density table to determine the liquid's mass.
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Does the phrase “Survival of the fittest” refer to an individual (single organism) or a species (group of same organisms)? Why?
The phrase "survival of the fittest," popularised in Charles Darwin's fifth edition of On the Origin of Species (published in 1869), argued that animals most adapted to their environment have the best chances of surviving.
What does "survival of the fittest" mean in terms of species?The environment and its conditions are continually changing, and the fittest individuals must generate even more fit offspring in order to ensure their survival. Here is when evolution comes into play.
Are organisms who are physically fitter more likely to survive and pass on their genes?An evolutionary mechanism is natural selection. Environment-adapted organisms have a higher chance of surviving and dispersing the genes that contributed to their success.
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A biochemist wanted to adjust the of of a buffer solution composed of ( ) and , by adding moles of. (assume the volume of the solution is not affected by this addition. ) determine the of the resulting solution:
The pH value of the resulting solution assume the volume of the solution is not affected by this addition is 3.283.
The pH scale determines how acidic or basic water is. The range is 0 to 14, with 7 representing neutrality. Acidity is indicated by pH values below 7, whereas baseness is shown by pH values above 7. In reality, pH is a measurement of the proportion of free hydrogen and hydroxyl ions in water.
In this Question, HF is a Weak Acid and RbF is a weak Base - HNO3 is a strong acid.
HF reaction in aqueous medium
HF + H2O --------- H3O+ + F -
RbF + H2O ---- Rb+ + F -
pH (Original) = pKa + log ( [salt ] / [Acid] )
We donot need to calculate pH original -which is for the original solution before adding the strong acid.
HF is a weak acid - so in a buffer solution its dissociation is negligible - so it does not affect the H+ ion concentration much.
When a 0.012 mol of HNO3 is added to the buffer solution , it dissociates in H+ and NO-3 .
H+ ions dissociated from the Acid react with F - and produce HF . As a result the acid concentration will increase to the extent of 0.012 mol and the salt concentration reduces by the same extent - 0.012 mol.
So the formula for New pH changes to
pH (New) = pKa + log ( [salt ] - 0.012 mol / [Acid] + 0.012 mol)
Here , 0.012 mol are added to 281 mL solution,
Concentration of HNO3, M = number of moles / Vol in litres
= 0.012 mol / 281 mL
= 0.012 mol / 281 / 1000
= [0.012 mol x 1000] / 281 L = 0.043 M
As pKa = -log(Ka) ,
Given [salt ] = 0.480 M , [Acid] = 0.318 M
= - log(Ka) + log [ (0.480 M - 0.043 M) / (0.318 M + 0.043 M) ]
= - log (6.31 x 10-4 ) + log ( 0.437 / 0.361)
pH (New) = 3.20 + 0.083 = 3.283.
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Complete question:
A biochemist wanted to adjust the pH of 281 mL of a buffer solution composed of 0.318 M HF and 0.480 M RbF (K, = 6.31e - 04) by adding 0.012 moles of HNO3. Determine the pH of the resulting solution: pH number (rtol=0.02, atol=1e-08)
a 3.83 g piece of limestone contains 2.57 g of c a c o 3 . based on these results, what is the mass percentage of c a c o 3 in limestone?
The mass percentage of CaCO₃ in the 3.83 g piece of limestone is 66.8%.
This can be calculated by taking the mass of CaCO₃ (2.57 g) and dividing it by the total mass of limestone (3.83 g) and multiplying by 100.
To calculate this, you need to take the mass of CaCO₃ (2.57 g) and divide it by the total mass of limestone (3.83 g).
This gives you a decimal value, which you then need to multiply by 100 to get the percentage value.
In this case, 2.57/3.83 = 0.668, which multiplied by 100 gives you 66.8%. This is the mass percentage of CaCO₃ in the limestone.
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a mixture of three gases has a total pressure of 1,380 mmhg at 298 k. the mixture is analyzed and is found to contain 1.27 mol co2, 3.04 mol co, and 1.50 mol ar. what is the partial pressure of ar? multiple choice 0.258 atm 301 mmhg 356 mmhg 5,345 mmhg 8,020 mmhg
The partial pressure of Ar is 0.219 * 1,380 mmHg = 301 mmHg.
The partial pressure of a gas in a mixture is equal to the mole fraction of that gas times the total pressure of the mixture.
The mole fraction of Ar in this mixture is 1.50/6.81 = 0.219. Thus, the partial pressure of Ar is 0.219 * 1,380 mmHg = 301 mmHg.
The ideal gas law states that the pressure of a gas is directly proportional to its number of moles and inversely proportional to its volume.
This law is expressed in the equation PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature.
In a mixture of gases, each gas behaves independently according to the ideal gas law. Thus, the total pressure of the mixture is the sum of the partial pressures of each gas.
The partial pressure of a gas is equal to its mole fraction times the total pressure. The mole fraction of a gas is the number of moles of that gas divided by the total number of moles of all gases in the mixture.
In the example provided, the total pressure of the mixture is 1,380 mmHg, the number of moles of CO2 is 1.27, the number of moles of CO is 3.04, and the number of moles of Ar is 1.50.
The total number of moles of all gases in the mixture is 1.27 + 3.04 + 1.50 = 6.81. The mole fraction of Ar is 1.50/6.81 = 0.219. Thus, the partial pressure of Ar is 0.219 * 1,380 mmHg = 301 mmHg.
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What do you think it means for a bond to have “more ionic” or “more covalent” character? Explain your thinking.
In summary, a bond having "more ionic" or "more covalent" character refers to the degree to which the bond is either purely ionic or purely covalent, with most bonds falling somewhere in between.
What does it mean to be more ionic or covalent?When a bond has more ionic character, it means that the electrons are transferred more completely from one atom to another, resulting in larger differences in electronegativity and a greater degree of charge separation between the atoms. This typically occurs when there is a large difference in electronegativity between the atoms involved in the bond.
On the other hand, when a bond has more covalent character, it means that the electrons are shared more equally between the atoms, resulting in a smaller difference in electronegativity and less charge separation. This typically occurs when the atoms involved in the bond have similar electronegativities.
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the empirical formula of a chemical substance is ch2. the molar mass of a molecule of the substance is 56.108 g/mol. what is the molecular formula of the chemical substance? (4 points) c3h4 c4h8 c2h4 c6h6
The molecular formula of the chemical substance is C4H8.
The empirical formula of a chemical substance, CH2, and its molar mass of 56.108 g/mol can be used to calculate the molecular formula of the substance.
In order to do this, we need to divide the molar mass by the empirical formula mass. The empirical formula mass for CH2 is 12.011 g/mol, so the calculation is: 56.108 g/mol / 12.011 g/mol = 4.67.
4.67, is the ratio of the molecular mass to the empirical formula mass.
This means that the molecular formula of the chemical substance is C4H8, which has a molecular mass of 4 x 12.011 g/mol = 48.044 g/mol, and is the closest molecular mass to the given molar mass of 56.108 g/mol.
Therefore, the molecular formula of the chemical substance is C4H8.
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what is the ph for a titration of 25.0 ml of 25.0 ml of 0.365 m acetic acid 0.365 m acetic acid when 10.3 ml of 0.432 m when 10.3 ml of 0.432 m naoh have been added?
The pH for a titration of 25.0 mL of 0.365 M acetic acid when 10.3 mL of 0.432 M NaOH have been added is approximately 4.69.
The pH for a titration of 25.0 mL of 0.365 M acetic acid when 10.3 mL of 0.432 M NaOH have been added can be calculated using the following steps:
1. Calculate the moles of acetic acid (CH₃COOH) and sodium hydroxide (NaOH) before the reaction:
- Moles of CH₃COOH = volume × concentration
= 25.0 mL × 0.365 mol/L
= 9.125 mmol
- Moles of NaOH = volume × concentration
= 10.3 mL × 0.432 mol/L = 4.4456 mmol
2. Determine the moles of acetic acid and sodium hydroxide remaining after the reaction: Since acetic acid and sodium hydroxide react in a 1:1 ratio, the limiting reactant will be NaOH.
- Moles of CH₃COOH remaining = 9.125 mmol - 4.4456 mmol = 4.6794 mmol - Moles of NaOH remaining = 0 mmol (all NaOH is consumed in the reaction)
3. Calculate the concentration of acetic acid and acetate ion (CH₃COO-) after the reaction:
- [CH₃COOH] = moles of CH₃COOH remaining / total volume
= 4.6794 mmol / (25.0 mL + 10.3 mL)
= 0.12998 mol/L
- [CH₃COO-] = moles of NaOH consumed / total volume
= 4.4456 mmol / (25.0 mL + 10.3 mL)
= 0.12346 mol/L
4. Calculate the pH using the Henderson-Hasselbalch equation:
pH = pKa + log([CH₃COO-] / [CH₃COOH]) pKa of acetic acid is 4.76, so:
pH = 4.76 + log(0.12346 / 0.12998) ≈ 4.69
Therefore, the pH for a titration of 25.0 mL of 0.365 M acetic acid when 10.3 mL of 0.432 M NaOH have been added is approximately 4.69.
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