Which of the following represents the number of moles of a solute in one liter of a solution?

1. Density

2. Molarity

3. Percent by mass

4. Volume

Question 2

The pH of a solution is 2.60. What is the [H3O+] for the solution?

1. 2.51 * 102 M

2. 3.98 * 102 M

3. 2.51 * 10-3 M

4. 3.98 * 10-3 M

Answer:Part 1

The right choice is (2) Molarity

Explanation:

Molarity is denoted by (M) and it is defined as the number of moles of solute (n) divided by the volume (V) of the solution in liters. We must keep in mind that the molarity is defined as moles of solute per liter of solution, not moles of solute per liter of solvent. In stichiometric calculations molarity is a unit of concentration.

Part 2Answer:

The right choice is (3) 2.51 * 10-3 M

Explanation:

As per definition of ph

pH = - log[H₃O⁺]

So putting the values

2.60 = - log[H₃O⁺]

log[H₃O⁺] = - 2.6.

We get

[H₃O⁺] = 2.51 x 10⁻³

Q1: 2. Molarity.

Q2: 2.51 x 10⁻³.

Explanation:

Q1:

The molarity is defined as the no. of moles of solute in one liter of solution. It is can be calculated from the relation: M = (no. of moles of solute) / (Volume in L of the solution).

Q2:

∵ pH = - log[H₃O⁺]

∴ 2.60 = - log[H₃O⁺]

log[H₃O⁺] = - 2.6.

∴ [H₃O⁺] = 2.51 x 10⁻³.