1.
The molar mass of solute is defined by
Correct Answer
A. 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.
How many particles are in the solution when CH₃OH is dissolved in water?
Correct Answer
A. 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.
3.
Adding solute particles will __________ the freezing temperature for a liquid solvent.
Correct Answer
C. 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".
4.
What are examples of colligative property?
Correct Answer
D. All of the above
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.
5.
What is the molar mass of Na₂CO₃?
Correct Answer
D. 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.
6.
The freezing point of a solution is __________, the freezing point of the pure solvent.
Correct Answer
A. Less than
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.
7.
What is the molar mass of calcium nitrate?
Correct Answer
C. 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.
8.
Avogadro’s number is equal to
Correct Answer
C. 6.02214076 × 1023 mol
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.
9.
Molality is measured in
Correct Answer
C. Mols per kg
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.
Correct Answer
A. Boiling, higher
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.