Answer:
To solve this problem, we can use the equation:
Q = m * c * ΔT
where Q is the heat transferred, m is the mass of the substance, c is its specific heat capacity, and ΔT is the change in temperature.
In this case, we know that the heat lost by the metal is equal to the heat gained by the water:
Q lost = Q gained
We can calculate the heat lost by the metal using the equation:
Q lost = m * c * ΔT
where m is the mass of the metal, c is the specific heat capacity of the metal (which we are trying to find), and ΔT is the change in temperature of the metal (100.5 C - 30.2 C = 70.3 C).
We can calculate the heat gained by the water using the equation:
Q gained = m * c * ΔT
where m is the mass of the water and ΔT is the change in temperature of the water (30.2 C - 20.0 C = 10.2 C).
Setting the two equations equal to each other, we get:
m * c * ΔT (metal) = m * c * ΔT (water)
Simplifying, we get:
c (metal) = (m * c * ΔT (water)) / (m * ΔT (metal))
Plugging in the values we know:
m (metal) = 32.8 g
ΔT (metal) = 70.3 C
m (water) = 138.2 g
ΔT (water) = 10.2 C
c (metal) = (138.2 g * 4.184 J/g·K * 10.2 C) / (32.8 g * 70.3 C)
c (metal) = 0.192 J/g·K
Therefore, the specific heat capacity of the metal is 0.192 J/g·K.
You have 400,000 atoms of a radioactive substance. After 2 half-lives have past, how many atoms remain?
Remember that you cannot have a fraction of an atom, so round the answer to the nearest whole number.
After 2 half-lives, 100,000 atoms of the radioactive substance will remain.
If two half-lives have passed, the number of remaining atoms will be one-fourth (1/2 x 1/2 = 1/4) of the original number of atoms.
Therefore, the number of remaining atoms will be:
400,000 x (1/4) = 100,000 atoms
Rounding this to the nearest whole number, we get:
100,000 atoms
Therefore after 2 half-lives, 100,000 atoms of the radioactive substance will remain.
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Pls answer these 9 questions I’ll mark the brainliest
1. Gases can be changed into liquids by _____.
A. adding heat
B. removing heat
C. none of the above
2. Which of the following is a true statement?
A. Smashing an object into many pieces changes its chemical composition.
B. Smashing an object into many pieces is a chemical change.
C. Smashing an object into many pieces does not change the object.
D. Smashing an object into many pieces is a physical change.
3.Match the physical forms of matter with their descriptions.
1. no fixed volume or shape _______liquid
2. fixed volume and shape _____solid
3. fixed volume but no fixed shape. _____gas
4. Which of the following is a true statement?
A. Melting is a biological change.
B. Melting is a chemical change.
C. Melting is a physical change.
D. Melting is a change made by humans.
5. How do substances differ after a chemical change?
A. The new substance is the same as the beginning substance.
B. The new substance is different from the beginning substance.
C. The new substance may or may not be the same as the beginning substance.
6. What factor is mostly responsible for the form of matter?
A.temperature
B.pressure
C.weather
D.time
7. Which of the following is a false statement?
A. solid substances need different temperatures to melt them.
B. All solid substances require the same temperature to melt them.
C. Heat is sometimes necessary to change physical property of an object.
8. Which of the following is a chemical change?
A. ice melting into water
B.an object broken into pieces
C.paper burning into ash
D.water changing to steam
9. When does heat produce a chemical change?
A.when heat energy is transferred
B.when heat changes ice into liquid water
C.when heat changes the chemical composition of an object
D.when heat is observed in an experiment
Answer:
below
Explanation:
1. B. removing heat.
The process of changing a gas into a liquid is called condensation. It occurs when the gas loses heat energy and its particles slow down and come closer together, eventually forming a liquid. Therefore, by removing heat from a gas, it can be changed into a liquid.
2. D. Smashing an object into many pieces is a physical change.
Smashing an object into many pieces does not change the chemical composition of the object. It only changes its physical appearance or state. A physical change is a change in the state or appearance of matter without any change in its chemical composition. Therefore, smashing an object into many pieces is a physical change.
3. No fixed volume or shape: gas
Fixed volume and shape: solid
Fixed volume but no fixed shape : liquid
4. C. Melting is a physical change.
Melting is the process of changing a solid substance into a liquid by heating it to its melting point. During this process, there is no change in the chemical composition of the substance, only a change in its physical state from solid to liquid. Therefore, melting is a physical change.Option A is incorrect because melting does not involve any biological process.
Option B is incorrect because melting does not result in any chemical reaction that alters the composition of the substance.
Option D is incorrect because melting is a natural physical phenomenon that occurs due to changes in temperature or pressure.
5. B. The new substance is different from the beginning substance.
In a chemical change, a chemical reaction occurs, which involves the breaking and formation of chemical bonds between atoms or molecules. This results in the formation of one or more new substances with different chemical properties than the original substances.
During a chemical change, the original substances are converted into new substances that have different physical and chemical properties, such as color, texture, odor, melting and boiling points, solubility, reactivity, etc. Therefore, the new substance is different from the beginning substance.
6. A. Temperature.
Temperature is the primary factor responsible for the form of matter. At different temperatures, matter exists in different states:
- At low temperatures, matter exists as a solid because the particles are tightly packed and have low energy, which keeps them in a fixed position.
- At higher temperatures, matter exists as a liquid because the particles have enough energy to move past each other but are still close together.
- At even higher temperatures, matter exists as a gas because the particles have enough energy to overcome the attractive forces between them and move independently.
Pressure can also influence the form of matter, but temperature is the primary factor that determines the state of matter. Weather and time are not factors that directly influence the form of matter.
7. B. All solid substances require the same temperature to melt them.
This statement is false. Different solid substances have different melting points, which is the temperature at which they change from a solid to a liquid. The melting point depends on the chemical composition and structure of the substance. Therefore, different solid substances require different temperatures to melt them.
Option A is a true statement because different solid substances have different melting points.
Option C is a true statement because heat can be used to change the physical property of an object, such as melting or boiling it.
8. C. Paper burning into ash.
This is a chemical change because burning paper involves a chemical reaction in which the cellulose fibers in paper combine with oxygen in the air to form new substances, such as water vapor, carbon dioxide, and ash. The chemical composition of the paper changes, and it cannot be reversed.
Option A is a physical change because melting ice into water involves only a change in physical state, not a change in chemical composition.
Option B is a physical change because breaking an object into pieces only changes its physical appearance, not its chemical composition.
Option D is a physical change because water changing to steam involves only a change in physical state, not a change in chemical composition.
9. C. When heat changes the chemical composition of an object.
Heat can produce a chemical change when it is used to break or form chemical bonds between atoms or molecules, resulting in a change in the chemical composition of the substance. This can lead to the formation of new substances with different chemical properties than the original substance. Therefore, option C is the correct statement.
Option A is incorrect because heat energy transfer can produce a physical change, such as melting or boiling, but not necessarily a chemical change.
Option B is incorrect because heat changing ice into liquid water is a physical change, not a chemical change.
Option D is incorrect because observing heat in an experiment does not necessarily produce a chemical change.
Can someone please help? And quickly if you can thank you!
The concept ideal gas equation is used here to determine the number of moles. The ideal gas law is the equation of state of a hypothetical ideal gas. Here the number of moles of gas is 0.17.
The equation which is formed by the combination of Boyle's law, Charles's law and Avogadro's law is called the ideal gas equation. An ideal gas is a theoretical gas composed of a set of randomly moving point particles which interact through elastic collisions.
The ideal gas equation is:
PV = nRT
n = PV / RT
10°C = 283 K
Number of moles is:
n = 1.2 × 3.4 / 0.0821 × 283 = 0.17
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1. (16 points) Shown below are IR and MS data for a compound with a molecular formula of C3H₂O
a) Identify the functional groups
responsible for the labeled
absorptions in the IR spectrum.
i) 1601 cm¹
ii) 1691 cm¹
Relative Intensity
100-
80-
m/z
rel. Intensity
22.6
73.1
105 100.0
120
26.2
$1.0
77.0
50 60
TRATT
100 110 120
1601 cm
1691 cm³
iii) From the parent,
what mass is lost to form
the base peak at m/z =
105?
iv) What is the likely
structure of that
fragment that is lost
to form m/z 105?
70
m/z
v) From the parent, what mass is lost to form the m/z = 77 peak?
Answer:
i) 1601 cm¹ - This absorption is likely from a C=O stretching vibration indicative of an aldehyde or ketone functional group.
ii) 1691 cm¹ - This absorption is likely from an O-H stretching vibration indicative of an alcohol functional group.
iii) From the parent, the mass lost to form the base peak at m/z = 105 is 17 amu.
iv) The likely structure of the fragment that is lost to form m/z 105 is C2H2O.
v) From the parent, the mass lost to form the m/z = 77 peak is 28 amu.
vi) The likely structure of the fragment that is lost to form m/z 77 is C2H3O.
Explanation:
A small sample of lead 5g (c=0.138 J/g°C) is placed into 50g of water at 25°C. What is the system’s final temperature if lead started at 50°C?
The system's final temperature is 25.825°C.
To solve this problem, we need to use the equation:
q = m × c × ΔT
where q is the heat absorbed or released, m is the mass of the substance, c is the specific heat capacity of the substance, and ΔT is the change in temperature.
In this case, the lead is losing heat to the water, so q will be negative. The water is gaining heat from the lead, so q will be positive.
First, let's calculate the amount of heat lost by the lead:
q_lead = -m_lead × c_lead × ΔT_lead
= -5 g × 0.138 J/g°C × (50°C - 25°C)
= -172.5 J
Next, let's calculate the amount of heat gained by the water :
[tex]q_{water}[/tex] = [tex]m_{water}[/tex] × [tex]c_{water}[/tex] × Δ[tex]T_{water}[/tex]
= 50 g × 4.184 J/g°C × ([tex]T_{f}[/tex] - 25°C)
where [tex]T_{f}[/tex] is the final temperature of the water
Since the total amount of heat lost by the lead is equal to the total amount of heat gained by the water (assuming no heat is lost to the surroundings), we can set [tex]q_{lead}[/tex] equal to [tex]q_{water}[/tex] and solve for [tex]T_{f}[/tex]:
- [tex]q_{lead}[/tex] = [tex]q_{water}[/tex]
172.5 J = 50 g * 4.184 J/g°C * ([tex]T_{f}[/tex] - 25°C)
[tex]T_{f}[/tex]- 25°C = 0.825
[tex]T_{f}[/tex] = 25°C + 0.825
[tex]T_{f}[/tex] = 25.825°C
Therefore, the system's final temperature is 25.825°C.
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Hydrazine, N2H4, reacts with oxygen to form nitrogen gas and water.
N2H4(aq)+O2(g)⟶N2(g)+2H2O(l)
If 3.45 g of N2H4 reacts with excess oxygen and produces 0.650 L of N2, at 295 K
and 1.00 atm, what is the percent yield of the reaction?
Four peripheral hydrogen atoms and two singly-bonded nitrogen atoms make up the molecule of hydrazine.
Thus, It is a colourless, poisonous irritant and sensitizer in its anhydrous form, which harms the central nervous system and causes symptoms as severe as tumours and convulsions.
In addition to having a strong reducing agent that makes it highly explosive, hydrazine has a strong smell that is similar to that of ammonia.
Given this, it appears odd that over 100,000 metric tonnes of the substance are produced annually throughout the world. But hydrazine does have an impact on our daily activities. It can save our lives, give us food and clothing, keep us warm, and even transport us to the moon. It even has the ability to go back in time.
Thus, Four peripheral hydrogen atoms and two singly-bonded nitrogen atoms make up the molecule of hydrazine.
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A soft drink contains 33g of sugar in 349g of H2O. What is the concentration of sugar in the soft drink in mass percent?
.
A soft drink contains 33g of sugar in 349g of H[tex]_2[/tex]O. 14.3% is the concentration of sugar in the soft drink in mass percent.
One approach to indicate the concentration of any dissolved component in a solution is by mass percentage. Mass percentage is the ratio of the total weight of a compound in a solution to the overall mass of the solution, expressed in percentages.
In order to express the mass percent of a solution, the grammes of solute are divided by the grammes of solution, and the result is multiplied by 100. As long as you use a comparable number for both the component and solute mass.
Mass percent = (mass of solute/mass of solute+ mass of solvent)×100
= ( 33/ 33+ 349)×100
=14.3%
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Which compound represents fe+3 o-2
Answer:
The compound that represents Fe+3 O-2 is Fe2O3 (iron oxide or rust)
A substance with a pH of 2 would be considered a strong what?
Answer:
A substance with pH 2 should be considered a strong acid.
Explanation
ph is a measure of how acidic or basic water is. The range goes from 0-14, with 7 being neutral.
pH of less than 7 indicate acidity and pH greater than 7 indicates base. So , the intensity of the acidic products increase as the pH decrease from 6 to 0 ,i.e. lower the value of pH higher will be the acidity.
With pH 2 given in the question it is considered as a strong acid.However , pH 2 acids are less acidic than acids having pH 0 and 1 but more acidic in compare to pH 3-6.
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Given the following equations and H° values, determine the heat of reaction at 298 K for the reaction: C(s) + 2 H2(g) -> CH4(g)
H2 (g) + 1/2 02 (g) -> H20 (l)
CO2 (g) + 2 H20 (l) -> CH4 (g) + 2 02 (g)
C(s) + O2(g) -›CO2(g)
H kJ = - 393.5
H kJ = -285.8
H kJ = +890.3
The heat of reaction for the reaction C(s) + 2 H2(g) -> CH4(g) at 298 K can be calculated by using the following equation: ΔH = (ΔHf products - ΔHf reactants).
Applying this equation to the given reaction, we get ΔH = (-890.3 + 393.5 + 285.8) kJ = -210.0 kJ.
This is the heat of reaction at 298 K for the reaction C(s) + 2 H2(g) -> CH4(g).
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Heat absorbed or released by a substance can be calculated with the equation _____________.
q = m × Cs × ∆T
q = m × Cs ÷ ∆T
q = m + Cs + ∆T
q = m + Cs
Calculate the final temperature (in Celsius) of HCI gas if 0.500 L at 42°C and 0.950 atm is heated
until the volume reaches 1.81 L at 0.950 atm. (deg C)
What is the amount (in mole) of sodium trioxocarbonate (IV) in 5.3g of the compound? (Na2CO3 = 106)
Answer:
To calculate the amount (in mole) of sodium trioxocarbonate (IV) in 5.3g of the compound , you can use the formula:
Amount (in moles) = Mass of substance / Molecular mass
The molecular mass of sodium trioxocarbonate (IV) (Na2CO3) is 106 g/mol, as given in the question. Substituting the values in the formula, we get:
Amount (in moles) = 5.3 g / 106 g/mol = 0.05 mol
Therefore, the amount (in mole) of sodium trioxocarbonate (IV) in 5.3g of the compound is 0.05 mol.
Note that the given molecular mass of Na2CO3 must be used to obtain the correct answe12 .
Explanation:
a 70 piece of metal at 120 C is dropped into a kilometer with 150 g of 30C water the final temperature of the water and little changes 35c what is the specific heat of the metal
A 70 piece of metal at 120 C is dropped into a kilometer with 150 g of 30C water the final temperature of the water and little changes 35c, 0.385 J/g°c is the specific heat of the metal.
The amount of heat needed to raise a substance's temperature by one degree Celsius in one gramme, also known as specific heat. Typically, calories and joules per gramme per degree Celsius are used as a measure of specific heat.
In the 18th century, the Scottish researcher Joseph Black found that equivalent masses of various substances required varying quantities of heat to bring them across the same temperature range. Based on this finding.
cm = (0.15 kg x 4.18 J/gCx (35C - 30C)) / (70 pieces x 0.1 kg/piece x (120C - 35C))
cm = 0.385 J/g°c
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At 2000 ∘c the equilibrium constant for the reaction 2no(g)⇌n2(g)+o2(g) is kc=2.4×103. You may want to reference (pages 641 - 644) section 15.6 while completing this problem. Part a if the initial concentration of no is 0.175 m, what is the equilibrium concentration of no? how is the quadratic equation set up i cannot get the right values
Please name this compound.
Answer:
The chemical name for this compound is 4-ethyl-2-methylhex-2-ene.
if this helps, please mark my answer as brainliest
HELP PLEASE!! DUE IN A FEW MINUTES!!
1) Aluminum and indium are in the same group
2) Barium is in group 2 and period 6
What is the periodic table?The names of the compounds are;
Triphosphorous tetrachloride
Calcium bromide
Nitrogen hexasulfur
The molecules that balance the charges are;
K3P, Al2O3, CaS
The elements in group 17 are chlorine and fluorine
The elements in period 3 are sodium and magnesium.
The balanced equations are from the data given;
SnO2 + 2H2 → Sn + 2H2O
4Al + 3O2 → 2Al2O3
Au2S3 + 3H2 → 2Au + 3H2S
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Assuming that the mass defect originates solely from the interactions of protons and neutrons in the nucleu, estimate the nuclear binding energy of Li given yhe following data.observee atomic mass (a.m.u) of Li is 7.01600u
1u=1.66054×10^-27kg
Electron rest mass= 9.10939×10^-31kg
Proton rest mass=1.67262×10^-27kg
Neutron rest mass=1.67493×10^-27kg
C=2.998×10^8
The mass lost in the formation of a nucleus is converted into energy in accordance with the Einstein's mass energy relationship and released, thereby tending to impart stability to the nucleus.
An input of the same amount of energy referred to as the binding energy would be required to decompose the nucleus into its component nucleons. So the energy released from the nucleons during the formation of a nucleus is called the binding energy.
No: of protons in 'Li' = 3
No: of neutrons in 'Li' = 4
Total mass of nucleons = 3(1.67262×10⁻²⁷) + 4 (1.67493×10⁻²⁷) = 1.171 × 10⁻²⁶ kg
Mass defect = 1.171 × 10⁻²⁶ - 1.165 × 10⁻⁻²⁶ = 6 × 10⁻²⁹
Binding energy = Δmc² = 6 × 10⁻²⁹ × (2.998×10⁸)² = 5.392 × 10⁻¹² J
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Reversible reactions allow products to create the reactants after a chemical reaction has gone from reactants to products. Which of the following is an example of a reversible reaction?
A) Oxygen combining with hemoglobin in red blood cells in our body, and then the red blood cells delivering the oxygen to needed locations\
B) Ammonium chloride separating into ammonia and hydrogen chloride gas
C)Hydrogen and oxygen combining to form water, and then water being broken down by a cell to be used in cellular respiration
D)All of the above
The nitrogen pressure at the Venusian surface is 2050 torr and the atmosphere of Venus is 3.0 mole% N2. What is the surface pressure on Venus in atm?
How many moles of KF are contained in 180.0 mL of a 0.250 M solution?
Answer:
To calculate the number of moles of KF in a solution, we can use the formula:
moles = concentration x volume
where concentration is in units of moles per liter (M), and volume is in liters (L).
First, we need to convert the volume from milliliters (mL) to liters (L):
180.0 mL = 0.1800 L
Next, we can plug in the values we have:
moles = 0.250 M x 0.1800 L = 0.0450 moles
Therefore, there are 0.0450 moles of KF in 180.0 mL of a 0.250 M solution.
Explanation:
This weather map showed the temperature (in °F) in the United States on a winter day. It also includes two pressure systems, labeled "H" and "L." Explain where weather fronts are most likely located, and predict the weather at each pressure system. edmentum science
Answer:
"H"is in California (High pressure cell brings cool conditions )it would be cool and the fronts are located on the coast of California."L"is in Utah (Low pressure cell brings warm conditions) it would be warmer. you let me know. I answeredit all the way.
N₂ +
H₂O →>>
NH, -
+
0₂
The balanced chemical equation for the reaction is:
N₂ + 3H₂O → 2NH₃ + O₂
The equation shows that nitrogen gas (N₂) and water (H₂O) react to form ammonia (NH₃) and oxygen gas (O₂). The coefficients in the balanced equation indicate that one molecule of N₂ reacts with three molecules of H₂O to produce two molecules of NH₃ and one molecule of O₂.
Question 3 of 10
How can the effect of heat on a reaction be determined?
A. Heat will increase reaction rate, but not equilibrium position.
B. Heat always shifts a reaction toward reactant formation.
C. Heat always shifts a reaction toward product formation.
D. Heat is treated as a reactant or a product.
SUBMIT
Saccharin (HNC7H4SO3) is a weak acid with pKa = 2.32 at 298 K.
a. Write a hydrolysis equation for the reaction of saccharin with water.
b. Calculate the pH of 0.10 M solution of saccharin.
c. Calculate the %ionization of the acid in this solution.
The pka or molarity of a solution may be used to calculate its pH. The saccharin solution in this area has a pH of 1.65.
The pH for a solution determines how acidic or basic it is. It refers to the opposite of the positive logarithm of the H+ ion concentration in maths. A solution that is acidic has a pH below 7, while a basic solution has a pH above 7.
Ka of an acid = [A-] [H+] / [HA]
ka = antilog (-pka)
= antilog (- 2.32)
= 0.0047
Ka = [H+]²/[HA]
[H+]² = Ka × [HA]
= 0.0047 × 0.11
= 0.00051
[H+] = 0.022.
pH = -log [H+]
= -log (0.022)
= 1.65
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please can someone fill the blanks, and/or tell me if this information SO FAR is accurate
it's just about pH levels, bases and acids
The acid base indicators or neutralization indicators are the substances which are employed for the visual detection of the end point in acid base titrations on account of their ability to change colour during the pH change that occurs in vicinity of the end point.
The characteristic pH range in which an acid-base indicator changes colour is called the colour change interval. This varies widely with different indicators. For water pH = 7, acidic solution has pH < 7 and basic solution has pH > 7.
The correct order of pH is:
13 > 10 > 9 > 6 > 4 > 3
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Calculate the percent ionization of 0.115 M lactic acid in a solution containing 7.0×10−3 M sodium lactate.
The percent ionization of 0.115 M lactic acid in a solution containing 7.0×[tex]10^-^3[/tex] M sodium lactate is 1.22% as percent ionization of a weak acid in solution is a measure of how much of the acid has dissociated into its ions.
The chemical equation for the dissociation of lactic acid is:
HC₃H₅O₃ ⇌ H+ + C₃H₅O₃−
The Ka value for lactic acid is 1.4×10^−4 at 25°C.
Initial: [HC₃H₅O₃]] = 0.115 M, [NaC₃H₅O₃] = 7.0×[tex]10^-^3[/tex] M, [H+] = 0 M, [C₃H₅O₃−] = 0 M
Using the Ka expression for lactic acid,
Ka = [H+][C₃H₅O₃−]/[HC₃H₅O₃]]
Substituting the equilibrium concentrations into the equation and solving for x,
1.4×[tex]10^-^4[/tex]= [tex]x^2[/tex]/(0.115−x)
Solving for x using the quadratic formula,
x =1.4×[tex]10^-^3[/tex] M
Now the percent ionization of lactic acid:
% Ionization = [H+]/[HC₃H₅O₃] × 100%
% Ionization = (1.4×[tex]10^-^3[/tex] M)/(0.115 M) × 100%
% Ionization = 1.22%
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A rubber balloon containing 1.0 L of gas is carried from the top of a mountain to the bottom of the mountain, where it’s volume is measured as .85 L at standard pressure. Assuming that there was no temperature change during the trip, what was the pressure in atmospheres at the top of the mountain?
Show steps pls
Answer:
the pressure at the top of the mountain was 0.85 atm.
Explanation:
We can use the combined gas law to solve this problem:
(P1 * V1) / (T1) = (P2 * V2) / (T2)
where P1, V1, and T1 are the initial pressure, volume, and temperature, and P2, V2, and T2 are the final pressure, volume, and temperature.
Assuming that the temperature remains constant, we can simplify the combined gas law to:
P1 * V1 = P2 * V2
where P1 and V1 are the initial pressure and volume, and P2 and V2 are the final pressure and volume.
Substituting the given values, we get:
P1 * 1.0 L = 1 atm * 0.85 L
P1 = (1 atm * 0.85 L) / 1.0 L
P1 = 0.85 atm
Substance A decomposes at a rate proportional to the amount of A present.
Write an equation relating A to the amount left of an initial amount Ao after time t.
It is found that 8 g of A will reduce to 4 g in 3 hr. After how long will there be only 1 g left?
It will take approximately 2.079 hours for there to be only 1 g of substance A left.
The rate of decomposition of substance A is proportional to the amount of A present, which means that we can use the following differential equation to describe the decay;
dA/dt = -kA
where A is the amount of substance A at time t, k is the rate constant of the reaction, and the negative sign indicates that A is decreasing over time.
To solve differential equation, we separate the variables and integrate;
[tex]d_{A}[/tex]/A = -k [tex]d_{t}[/tex]
Integrating both sides gives;
ln(A) = [tex]-k_{t}[/tex] + C
where C is the constant of integration. To find the value of C, we can use the initial condition that 8 g of A reduces to 4 g in 3 hours. At t=0, A=Ao=8 g, and at t=3, A=4 g. Substituting values into the equation above, we have;
ln(8) = -3k + C
ln(4) = -6k + C
Subtracting first equation from second, we get;
ln(4/8) = -3k
Simplifying, we get;
k = ln(2)/3
Now, we can use the equation we derived earlier to find how long it will take for there to be only 1 g of A left;
ln(A) =[tex]-k_{t}[/tex] + C
ln(1) = -(ln(2)/3)t + C
Simplifying, we get:
t = 3 ln(2)
t ≈ 2.079 hours
Therefore, it will take 2.079 hours.
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The empirical formula of caffeine is C4H5N2O. If the molar mass of caffeine is 194.19 g/mol, what is the molecular formula of caffeine?
The molecular formula of caffeine is C₈H₁₀N₄O₂
To find the molecular formula of caffeine, we need to determine the ratio of the empirical formula to the actual molecular formula. The empirical formula gives us the smallest whole-number ratio of atoms in a compound, while the molecular formula gives us the actual number of atoms of each element in a molecule.
First, we need to calculate the empirical formula mass of caffeine:
Empirical formula mass = (4 x atomic mass of carbon) + (5 x atomic mass of hydrogen) + (2 x atomic mass of nitrogen) + (1 x atomic mass of oxygen)
Empirical formula mass = (4 x 12.01 g/mol)+ (5 x 1.01 g/mol) + (2 x 14.01 g/mol) + (1 x 16.00 g/mol)
Empirical formula mass = 96.09 g/mol
Next, we can calculate the ratio of the molar mass of caffeine to the empirical formula mass:
Ratio = Molecular mass / Empirical formula mass
Ratio = 194.19 g/mol / 96.09 g/mol
Ratio = 2.02
This ratio tells us that the molecular formula of caffeine is approximate twice the size of the empirical formula. To find the molecular formula, we can multiply the subscripts in the empirical formula by the ratio:
C₄H₅N₂O × 2 = C₈H₁₀N₄O₂
Therefore, the molecular formula of caffeine is C₈H₁₀N₄O₂.
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