How do you calculate mass of a known substance (sodium chloride for example) given its amount in terms of moles? O multiply moles by the molar mass O divide moles by the molar mass O cannot be determined based on the given divide the molar mass by the Avogadro's number

Heating to constant mass is done to retain the constant mass of the sample so that its weight remains the same and does not affect the reading throughout the experiment.

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When something heats up energy is absorbed from another system and when something cooler down energy is released to another system.

When a reaction releases heat, it is classified as exothermic. The absorption of heat in a reaction makes it endothermic.

In order to find the pressure in this situation, we will be using the Ideal gas Law, which perfectly correlates these informations, the formula for this Law is:

PV = nRT

Where:

P = pressure, we want to find it

V = volume, 1.00 L

n = number of moles, we will also find it

R = is the gas constant, 0.082

T = 301 K

To find the number of moles, we need to use the mass provided in the question and also the molar mass of CO2, 44.01g/mol

44.01g = 1 mol

7.94g = x moles

x = 0.180 moles of CO2

Now we can use the ideal gas formula:

P * 1.00 = 0.180 * 0.082 * 301

P = 4.44 atm

Considering the definition of STP conditions, 4.83 × 10⁻³ moles of HF will occupy a volume of 0.108192 L at STP.

The STP conditions refer to the standard temperature and pressure. Pressure values at 1 atmosphere and temperature at 0 ° C are used and are reference values for gases, and 1 mole of any gas occupies an approximate volume of 22.4 liters.

In this case, you have 4.83×10⁻³ moles of HF. You can apply the following rule of three: if by definition of STP conditions 1 mole of HF occupies a volume of 22.4 liters, 4.83×10⁻³ moles occupies how much volume?

volume= (4.83×10⁻³ moles ×22.4 L)÷ 1 mole

volume= 0.108192 L

Finally, there is a volume of 0.108192 L at STP.

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Answer:

Explanations:

a) The balanced chemical reaction for the complete combustion of pentane is expressed as:

Note that oxygen, carbondioxide and water are all in gaseous state.

The boiling point of the solution is 80.93°C.

We know that the boiling point has to do with the temperature at which the pressure inside the system is the same as the atmospheric pressure. Now we know that the boiling point of the pure benzene is 80.1 °C.

Also;

ΔT = K m i

ΔT = boiling point elevation

K = boiling point constant

m = molality

i = Van Hoff factor

ΔT = 2.53°C /m * 0.33 m * 1

ΔT =  0.83°C

Boiling point of the solution =  0.83°C + 80.1 °C

= 80.93°C

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The question requires us to calculate the amount of moles of water that we would have in 5.3x10^26 molecules of water.

To solve this problem, we'll need to consider the Avogadro Number: this number states the amount of particles (electrons, ions, atoms, molecules etc.) in one mole of a substance. The Avogadro Number corresponds to 6.022 x 10^23 particles per mol.

Considering the Avogadro number and the number of molecules provided by the question, we can write:

6.022 x 10^23 molecules of water -------------------- 1 mol of water

5.3 x 10^26 molecules of water ------------------------ x

Solving for x, we'll have:

Therefore, there are 8.8 x 10^2 moles of water in 5.3 x 10^26 molecules of water.

Answer:

A

Explanation:

In-house forensics allows companies to work faster, cheaper, and potentially better than law enforcement. Labs at large companies are more likely than police labs to have high-tech tools and the latest forensics software, said Seigfried-Spellar.

Nuclear fission causes a neutron to split the isotope U-235 when it collides with its nucleus. When a slow neutron interacts with a heavy nuclide like 235U, nuclear fission can occur (0.025 eV).

When a slow neutron interacts with a heavy nuclide like 235U, nuclear fission can occur (0.025 eV). If a fission (or splitting apart) occurs, the nuclear material splits into two (on average) about equal fragments that travel away with kinetic energy, producing heat.

Nuclear fission causes a neutron to split the isotope U-235 when it collides with its nucleus. Two or three additional neutrons as well as fission products are released during this fission process. The chain reaction is continued by some of the emitted neutrons. There is significant energy released in every fission reaction.

When a uranium atom divides, additional neutrons are also released. The process keeps repeating again as these neutrons keep crashing into more uranium atoms. This process is called a nuclear chain reaction. This reaction is controlled in nuclear power plant reactors to produce a desired amount of heat.

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Answer:

Explanation:2H2 + O2 —-> 2H2O

The mole ratio of H2 to H2O is 2 : 2 = 1:1

4 moles of H2 = 4 moles of H2O

Moles of H20 = 4mol

Molar mass of H2O = 18g/mol

Mass = moles X Molar mass

= 4mol x 18g/mol

= 72g

Answer:

b Different amounts of food samples were used.

Explanation:

The mass of the two samples needs to be the same in order for the test to be accurate.

There are many legends of the North Star that have been told over the years by different civilizations and of them is a mythical story told about the existence of the star.

It is said that it is a little dot left behind after God created the stars and based on the fact that the dot was not like the other stars as it was almost an afterthought and then it came to the attention of Luminaria who granted the dot its wish and it became a real star like the others and became the Star of Bethlehem.

Hence, it can be seen that the given legend and mythical stories are just one of the many ways humans try to understand the phenomena of astrology and how they attach certain significance to it.

With this in mind, it is very clear to see that the North Star is a special star.

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In order to calculate this question, we will use the reaction quotient Q, which has a very similar formula as the equilibrium formula, but this Q can be calculated not just in equilibrium (where Q = K) but in any part of the reaction, so K is the equilibrium, and Q is what is used to see where the reaction will shift towards until it reaches equilibrium, we can have three possible outcomes:

Q = K, the reaction is already in equilibrium

Q > K, the reaction will proceed in the reverse direction

Q < K, the reaction will proceed in the forward direction

Let's set up the formula:

Q = [products]/[reactants], the brackets mean Concentration of each compound. Now adding our compounds

Q = [BrCl]^2/[Br2]*[Cl2], the BrCl is raised to 2 because we have 2 BrCl in the reaction, this is a rule for the equilibrium formula, we use the coefficient in front of the compound and raise its concentration to this number

Now we need the concentration of each compound, to find it we will use the Molarity formula

M = n/V

M = 0.15/2

M = 0.075M, notice that since we have the same number of moles and volume for every compound, we will have the same concentration for every compound, going back to our formula

Q = [0.075]^2/[0.075][0.075]

Q = 1.0

Since K = 7.0 and Q = 1.0

K > Q, the reaction will proceed in the forward direction in order to increase the concentration of 2 BrCl in order to finally reach Q=K

Answer:

The Chlorine atom has higher ionization energy.

Explanation:

Ionization energy is the energy needed to separate an electron from an atom of an element in the gaseous state.

In the Periodic Table of Elements, Ionization energy increases from bottom to top (in a group), and increases from left to right (in a period).

In the folowing drawing we can see the variation of the Ionization energy and the location of the magnesium atom and chlorine atom:

Magnesium atom and Chlorine atom are located in the same period, but Mg is in group 2 (left side) and Cl in in group 17 (right side), so the Chlorine atom has higher ionization energy.

The correct statement about the description of ion whose symbol is Ca2+ among the choices above are:

The options b and d are correct.

It follows that elements whose charge on them are positive are called cations. In order words, in the periodic table of science of chemistry, the positively charged ions of elements are known as cations. Calcium has a positive of 2 on as it ion and this makes it a cation.

In addition to the above, calcium ion helps in signal transduction pathways of cells of living organisms. This goes to say that they also help in the body's normal functioning of the human body.

However, on a second note, calcium in the periodic table belongs to group 2, has a valence electrons of 2 and a metallic element; thereby making it a divalent metal.

In conclusion, we can now confirm from all said above that calcium above is a cation.

Complete question:

Check all of the following statements that are true about the ion whose symbol Ca2+

a. It is an anion

b. It is a cation

c. Its atoms is connected by tripple bonds

d. It is a divalent metal

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2. Which is the volume of 3.20 moles of O₂?

We are told that at STP one mol of any gas occupies 22.4 L. We will use that relationship to find the volume occupied by 3.20 moles of O₂.

1 mol of O₂ = 22.4 L

volume of O₂ = 3.20 moles of O₂ * 22.4 L/(1 mol of O₂)

volume of O₂ = 71.7 L

Answer: 3.20 moles of O₂ occupies 71.7 L

7. Which is the volume of 100. g of O₂?

In this case we will use the same relationship, but we are given grams instead of moles. So first we have to convert the mass in grams into moles. To do that we use the molar mass of O₂.

atomic mass of O = 16.00 amu

molar mass of O₂ = 2 * 16.00

molar mass of O₂ = 32.00 g/mol

Once that we know that the mass of 1 mol of O₂ is 32.00 g, we can find the number of moles that we have in 100. g of it.

moles of O₂ = mass of O₂ /(molar mass of O₂)

moles of O₂ = 100. g/(32.00 g/mol)

moles of O₂ = 3.13 moles

Finally we can find the volume that 3.13 moles of O₂ occupies (remember that 1 mol of any gas occupies 22.4 L at STP).

volume of O₂ = 3.13 moles * 22.4 L/(1 mol)

volume of O₂ = 70.1 L

Answer: 100. g of O₂ occupies 70.1 L

3.786137931L of chlorine are needed.

1st) It is necessary to write the balanced equation of the reaction between chlorine gas (Cl2) and sodium (Na) to produce sodium chloride (NaCl):

Now we know that 1 mol of chlorine gas is needed to react with 2 moles of sodium in the production of sodium chloride. With the molar mass of Na (23.0g/mol) and Cl2 (71.0g/mol), we can see that 71.0g of Cl2 are needed to react with 46.0g of sodium.

2nd) Knowing that 71.0g of Cl2 are needed to react with 46.0g of sodium, we can use a mathematical rule of three to calculate the amount of Cl2 that will react completely with 12.0g of sodium:

3rd) Now it is necessary to convert the mass of chlorine gas into moles, so we can use it in the Ideal gas formula:

So, 0.26 moles of chlorine gas are needed.

4th) With the formula of Ideal gases and replacing the values of Pressure (P), number of moles (n) and Temperature (T, in Kelvin), we can calculate the volume of Cl2:

Finally, 3.786137931L of chlorine are needed to react completely with 12.0g of sodiu.

The final temperature of the solution is  20 °C.

Given that :

volume of HNO₃ = 0.33 L

molarity = 0.500 M

no. of moles HNO₃ = 0.33 × 0.500

                     = 0.165 mol

moles of Ba(OH)₂ = 0.33 × 0.250

                             = 0.082 mol

Q = ΔH × n

Q = - 52600 J/mol × 0.165 mol

Q = - 8679 J

total volume = 330 mL +330 mL = 660 mL

Density = mass / volume

mass = 1 g/mL × 660 mL

mass = 660 g/mL

now, the change in temperature can be calculated by following formula :

Q = mc ( ΔT )

Q = mc ( T2 - T1 )

- 8679 = 660× 4.184 ( T2 - 18.46 °C)

T2 = 20 °C

Thus, A quantity of 3.30 × 10² mL of 0.500 M HNO3 is mixed with 3.30 × 10² mL of 0.250 M Ba(OH)₂ in a constant-pressure calorimeter of negligible heat capacity. The initial temperature of both solutions is the same at 18.46°C. The heat of neutralization when 1.00 mol of HNO₃ reacts with 0.500 mol Ba(OH)₂ is −56.2 kJ/mol. Assume that the densities and specific heats of the solution are the same as for water (1.00 g/mL and 4.184 J/g · °C, respectively).  the final temperature of the solution is 20 °C.

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2 oxygen ions

Oxygen is a non-metal with an atomic number of 8. The electronic configuraton of the element is given as:

If a an unknown metal with a charge of 4 combines with oxygen, the required reaction will be:

Since oxygen is in group VI of the periodic table and has a oxidation number of -2, to form a neutral compound with charge of +4, this means that 2 oxygen ion will combine with the metal to form a neural compound MO2

There are some compounds in which the electrons move from one side to anothe, and it is a continous movement. For that reason, the resonance structure is created. It works as a theorical structure which is not exact, but it helps us to approach to the real structure.

For example, for the bencene, there are 3 different resonance structures:

And they are the same compound. It means that the answer is B. Alternate structures of the same compound.

5998kJ

Given the reaction between ethanol and oxygen expressed as:

For the product

We have 2 moles of CO2 and 3 moles of water. The total bond energy in the product is expressed as:

Hence the total energy transferred to build all the bond energy in the product is 5998kJ

Some atoms are neutral and others have positive or negative charges.

The charged atoms are called "ions".

- If the ion has positive charge, it is called cation.

- If the ion has negative charge, it is called anion.

Ions can be identified by their charge, for example:

- Cations: Na^+1, K^+1, Mg^+2

- Anions: Cl^-1, Br^-1

It is the same for every sample of every substance present describes an intensive property of matter.

The correct option is C.

An intense property is a greater stability of a system that is independent of the system's size or the volume of its constituent elements. Based on the definitions, internal energy, volume, or density are extensive properties while pressure, temperature, and densities are intensive properties.

Because of the small range of densities present among the samples, density is an intense attribute. Concentrations were roughly the same regardless of the beginning mass. The data show that density is an intense attribute of matter because it is independent of the amount of substance present.

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The complete question is

Which statement describes an intensive property of matter?

A-It is the same for every sample of a single substance.

B-It depends on how a substance was formed.

C-It is the same for every sample of every substance.

D-It depends on the amount of substance present.

The reaction to produce nitrogen dioxide from nitrogen and oxygen is as follows:

Since all the reactants and products are gases, we can take the coefficients as liters of substance.

Dividing the volumes we have of each reactant by their corresponding coefficient we can determine the limit reagent:

From this we can conclude that the limit reagent is oxygen.

We have to base our calculations on this substance.

According to the given equation, 2 L of O2 produce 2 L of NO2, use this ratio to find the volume of nitrogen dioxide produced:

It means that 60.6 liters of nitrogen dioxide gas are made.

This organic compound has in its structure the next element: C, H, and O

45.27% C

4.43 % H

The rest 100%-45.27%-4.43 = 50.3 % O

-----------------------------------------------------------------------------------------------------------------

The empirical formula of a chemical compound is the simplest whole-number ratio of atoms present in a compound.

Procedure:

Step 1)

We convert % into grams (g). Let's assume we have a 100g sample. Therefore,

45.27 % C = 45.27 g

4.43 % H = 4.43 g

50.3 % O = 50.3 g

Step 2)

We calculate the number of moles of each element. To do this, we need every atomic mass

For C)

For H)

For O)

Step 3)

We divide all moles by the smallest one of them (3.14 moles of O)

For C) 3.767 moles/3.14 moles = 1.19 = 1 (we need integer numbers)

For H) 4.43 moles/3.14 moles = 1.41 = 1

For O) 3.14 moles/3.14moles = 1

The empirical formula is CHO

The percentage of the sample of As-81 remaining undecayed after 43.2 seconds is 40.6%

We'll beging by calculating the number of half lives that has elapsed. This can be obtained as follow

The following data were obtained from the question:

n = t / t½

n = 43.2 / 33

n = 1.3

Finally, we shall determine the percentage remaining undecayed. This is shown below:

N = N₀ / 2ⁿ

N = 100 / 2^1.3

N = 40.6%

Thus, we can conclude that the percenatge undecayed is 40.6%

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Answer:

Explanation:

The chemical reaction talks about the synthesis of calcium carbonate

It is from the reaction between sodium carbonate and calcium chloride

Let us write the equation of reaction as follows:

Firstly, we want to get the expected mass of calcium carbonate

This speaks about getting the theoretical yield based on the equation of reaction

From the data collected, 90 ml of 0.20 M (mol/L) of sodium carbonate gave calcium carbonate

We need to get the actual number of moles of sodium carbonate that reacted

We can get this by multiplying the volume by the molarity (kindly note that we have to convert the volume to Liters by dividing by 1000)

Thus, we have it as:

Hence, we see that 0.009 moles of sodium carbonate reacted theoretically

Since 1 mole of sodium carbonate gave 1 mole calcium carbonate, it is expected that 0.009 mole of sodium carbonate will give 0.009mole of calcium carbonate

What we have to do now is to get the theoretical grams of calcium carbonate produced

That would be the product of the number of moles of calcium carbonate and its molar mass

The molar mass of calcium carbonate is 100 g/mol

The theoretical yield (expected mass) is thus:

Finally, we proceed to get the percentage yield which is calculated using the formula below:

The actual yield is the observed mass which is given as 0.88 g

The percent yield is thus:

Answer:

Explanation:

Here, we want to get the molar mass of the gas

Let us call it M

From the ideal gas equation, we can get the number of moles of the gas

Mathematically:

Also, n is the mass divided by the molar mass of the gas:

Where:

M is the molar mass that we want to calculate

m is the mass of the gas sample which is 1.45 g

P is the gas pressure which is 733 torr (to convert to atm, we multiply by 0.00131579 : 733 * 0.00131579 = 0.96 atm)

V is the volume which is 931 mL (We convert to L by dividing by 1000:

931/1000 = 0.931 L)

R is the molar gas constant which is 0.0821 L.atm/mol.K

T is the temperature that we convert to K by adding 273 K : 273 + 16 = 289 K)

Substituting the values, we have it that: