Question

Cooks use baking soda to make cakes light and fluffy. You might have used baking soda yourself. Baking soda is NaHCO3. A 0.1 M solution of baking soda in water has a [H+] of about 4.0 × 10–9. (You may prefer to think of the hydronium ion concentration, [H3O+], as 4.0 × 10–9.) Write the formula for the calculation of pH, and then show each step as you calculate the pH of a 0.1 M solution of baking soda.

Answer 1

PH = -log [H⁺] ←←[log without a specified base means log base 10] 

and if you want to use the hydronium ion concentration then use pH = -log [H₃O⁺] 

either way the calculation is the same: 


They give that a 0.1 M solution of NaHCO₃ has a hydrogen ion concentration of 4.0 x 10^(-9) 

so pH = -log (4.0 x 10^(-9)) 

pH = 8.4