Question

A solution is prepared by dissolving 0.23 g of sodium oxide in water to give 133.0 ml of solution. Express the pH to two decimal places.

a) 10.45

b) 11.78

c) 12.34

d) 9.02

Answer 1

To find the pH of a solution, divide the mass of sodium oxide by its molar mass to calculate the number of moles, then use the volume of the solution to find the concentration of hydroxide ions. Finally, use the equation pH = -log[OH-] to find the pH of the solution.

Step-by-step explanation:

To find the pH of a solution, we need to determine the concentration of hydroxide ions (OH-) in the solution. The number of moles of sodium oxide can be calculated by dividing the mass of sodium oxide by its molar mass. Then, we can use the volume of the solution to calculate the concentration of hydroxide ions. Finally, we can use the equation pH = -log[OH-] to find the pH of the solution.

Let's go through the calculation:

First, calculate the number of moles of sodium oxide:

moles of Na₂O = mass / molar mass = 0.23 g / 62 g/mol = 0.00371 mol

Next, calculate the concentration of hydroxide ions:

concentration = moles / volume = 0.00371 mol / 0.133 L = 0.0278 M

Finally, calculate the pH:

pOH = -log(0.0278) = 1.56

pH = 14 - pOH = 14 - 1.56 = 12.44