Question

1. 7.00×10⁻³ mol of HBr are dissolved in water to make 19.0 L of solution. What is the concentration of hydroxide ions, [OH−], in this solution?

2. 4.00 g of NaOH are dissolved in water to make 5.00 L of solution. What is the concentration of hydronium ions, [H3O+], in this solution?

Answer 1

1. 7.00×10−3 mol of HBr are dissolved in water to make 19.0 L of solution. What is the concentration of hydroxide ions, [OH−], in this solution?

find concnetratino of HBr first

[HBr] = mol/V = (7*10^-3)/(19) = 0.00036842105

Then [h+] = 0.00036842105

[OH-] = Kw/H+

Kw = 10^-14

[OH-] = (10^-14)/(0.00036842105) = 2.714*10^-11

[OH-] =2.714*10^-11

2)

m = 4 gof NaOh

V = 5 L

MW of NaOH = 40 then

mol = mass/MW = 4/40 = 0.1

M = 0.1/5 = 0.02

[OH-] = 0.02

then

[h+] = Kw/[OH-] = (10^-14)/(0.02) = 5*10^-13

[H+] = 5*10^-13