Molar Mass From Freezing And Boiling Point Quiz

1. The molar mass of solute is defined by

Mass of solute/number of moles of solute

Mass of solvent/number of moles of solute

Mass of solute/number of moles of solvent

None of the above

The molar mass of a solute is defined as the mass of the solute divided by the number of moles of the solute. This definition is based on the concept of molar mass, which is the mass of one mole of a substance. In this case, the numerator represents the mass of the solute, while the denominator represents the number of moles of the solute. Therefore, the correct answer is "mass of solute/number of moles of solute".

Explanation

The molar mass of a solute is defined as the mass of the solute divided by the number of moles of the solute. This definition is based on the concept of molar mass, which is the mass of one mole of a substance. In this case, the numerator represents the mass of the solute, while the denominator represents the number of moles of the solute. Therefore, the correct answer is "mass of solute/number of moles of solute".

2. What are examples of colligative property?

Boiling Point Elevation

Freezing Point Depression

Osmotic Pressure

All of the above

The examples provided, boiling point elevation, freezing point depression, and osmotic pressure, are all types of colligative properties. Colligative properties depend on the number of solute particles present in a solution, rather than the identity of the solute. Boiling point elevation occurs when the boiling point of a solvent increases due to the presence of a solute. Freezing point depression refers to the lowering of the freezing point of a solvent caused by the addition of a solute. Osmotic pressure is the pressure required to prevent the flow of solvent across a semipermeable membrane, and it is also a colligative property.

Explanation

The examples provided, boiling point elevation, freezing point depression, and osmotic pressure, are all types of colligative properties. Colligative properties depend on the number of solute particles present in a solution, rather than the identity of the solute. Boiling point elevation occurs when the boiling point of a solvent increases due to the presence of a solute. Freezing point depression refers to the lowering of the freezing point of a solvent caused by the addition of a solute. Osmotic pressure is the pressure required to prevent the flow of solvent across a semipermeable membrane, and it is also a colligative property.

3. The freezing point of a solution is __________, the freezing point of the pure solvent.

Less than

Greater than

Equal to

None of the above

A solution is formed when a solute is dissolved in a solvent. The presence of the solute particles disrupts the regular arrangement of the solvent particles, making it more difficult for the solvent to freeze. As a result, the freezing point of a solution is lower than the freezing point of the pure solvent. This phenomenon is known as freezing point depression.

Explanation

A solution is formed when a solute is dissolved in a solvent. The presence of the solute particles disrupts the regular arrangement of the solvent particles, making it more difficult for the solvent to freeze. As a result, the freezing point of a solution is lower than the freezing point of the pure solvent. This phenomenon is known as freezing point depression.

4. Adding solute particles will __________ the freezing temperature for a liquid solvent.

Increases

Does not affect

Decreases

All of the above

When solute particles are added to a liquid solvent, they disrupt the regular arrangement of solvent particles, making it more difficult for the solvent to form a solid lattice structure. This disruption lowers the freezing point of the solvent, causing the freezing temperature to decrease. Therefore, the correct answer is "decreases".

Explanation

When solute particles are added to a liquid solvent, they disrupt the regular arrangement of solvent particles, making it more difficult for the solvent to form a solid lattice structure. This disruption lowers the freezing point of the solvent, causing the freezing temperature to decrease. Therefore, the correct answer is "decreases".

5. What is the molar mass of calcium nitrate?

162.1 g/mol

163.1 g/mol

164.1 g/mol

None of the above

The molar mass of calcium nitrate is 164.1 g/mol. This can be determined by adding up the atomic masses of the elements in the compound: calcium (Ca) has a molar mass of 40.08 g/mol, nitrogen (N) has a molar mass of 14.01 g/mol, and oxygen (O) has a molar mass of 16.00 g/mol. The compound has one calcium atom, two nitrogen atoms, and six oxygen atoms, so the total molar mass is calculated as (1 * 40.08) + (2 * 14.01) + (6 * 16.00) = 164.1 g/mol.

Explanation

The molar mass of calcium nitrate is 164.1 g/mol. This can be determined by adding up the atomic masses of the elements in the compound: calcium (Ca) has a molar mass of 40.08 g/mol, nitrogen (N) has a molar mass of 14.01 g/mol, and oxygen (O) has a molar mass of 16.00 g/mol. The compound has one calcium atom, two nitrogen atoms, and six oxygen atoms, so the total molar mass is calculated as (1 * 40.08) + (2 * 14.01) + (6 * 16.00) = 164.1 g/mol.

6. Avogadro's number is equal to

6.03214076 × 1023 mol

6.02214076 × 1022 mol

6.02214076 × 1023 mol

6.02214076 × 1024 mol

Avogadro's number is a fundamental constant in chemistry and physics that represents the number of atoms or molecules in one mole of a substance. The correct answer is 6.02214076 × 10^23 mol, which is the most widely accepted value for Avogadro's number. This means that there are approximately 6.02214076 × 10^23 atoms or molecules in one mole of any substance.

Explanation

Avogadro's number is a fundamental constant in chemistry and physics that represents the number of atoms or molecules in one mole of a substance. The correct answer is 6.02214076 × 10^23 mol, which is the most widely accepted value for Avogadro's number. This means that there are approximately 6.02214076 × 10^23 atoms or molecules in one mole of any substance.

7. What is the molar mass of Na₂CO₃?

103 g/mol

104 g/mol

105 g/mol

105.9888 g/mol

The molar mass of Na₂CO₃ is 105.9888 g/mol because it is the sum of the atomic masses of each element in the compound. Na has a molar mass of 22.99 g/mol, C has a molar mass of 12.01 g/mol, and O has a molar mass of 16.00 g/mol. Multiplying the molar mass of Na by 2 (since there are 2 Na atoms), and adding the molar masses of C and 3 O atoms gives a total molar mass of 105.9888 g/mol.

Explanation

The molar mass of Na₂CO₃ is 105.9888 g/mol because it is the sum of the atomic masses of each element in the compound. Na has a molar mass of 22.99 g/mol, C has a molar mass of 12.01 g/mol, and O has a molar mass of 16.00 g/mol. Multiplying the molar mass of Na by 2 (since there are 2 Na atoms), and adding the molar masses of C and 3 O atoms gives a total molar mass of 105.9888 g/mol.

8. How many particles are in the solution when CH₃OH is dissolved in water?

1

2

3

4

When CH₃OH (methanol) is dissolved in water, it forms a homogeneous solution. In a solution, the solute particles (methanol molecules) are evenly distributed and mixed with the solvent particles (water molecules). The solution is considered as one phase, so there is only one set of particles present in the solution. Therefore, the correct answer is 1.

Explanation

When CH₃OH (methanol) is dissolved in water, it forms a homogeneous solution. In a solution, the solute particles (methanol molecules) are evenly distributed and mixed with the solvent particles (water molecules). The solution is considered as one phase, so there is only one set of particles present in the solution. Therefore, the correct answer is 1.

9. Molality is measured in

Mols per g

Mols per L

Mols per kg

All of the above

Molality is a measure of the concentration of a solute in a solution. It is defined as the number of moles of solute per kilogram of solvent. Therefore, the correct answer is "mols per kg" because molality is measured in moles per kilogram. This unit is preferred over mols per g or mols per L because it is independent of temperature and pressure, making it a more accurate representation of the concentration of a solution.

Explanation

Molality is a measure of the concentration of a solute in a solution. It is defined as the number of moles of solute per kilogram of solvent. Therefore, the correct answer is "mols per kg" because molality is measured in moles per kilogram. This unit is preferred over mols per g or mols per L because it is independent of temperature and pressure, making it a more accurate representation of the concentration of a solution.

10. The ____________ point of the solution is _________ than the pure solvent.

Boiling, higher

Melting, higher

Boiling, lower

Melting, higher

Option 5

The boiling point of a solution is higher than that of the pure solvent. This is because when a solute is added to a solvent, the solute particles disrupt the intermolecular forces between the solvent particles, making it more difficult for the solvent to change from a liquid to a gas state. As a result, a higher temperature is required to reach the boiling point of the solution compared to the boiling point of the pure solvent.

Explanation

The boiling point of a solution is higher than that of the pure solvent. This is because when a solute is added to a solvent, the solute particles disrupt the intermolecular forces between the solvent particles, making it more difficult for the solvent to change from a liquid to a gas state. As a result, a higher temperature is required to reach the boiling point of the solution compared to the boiling point of the pure solvent.