Question

Potassium hydrogen phthalate is a solid, monoprotic acid frequently used in the laboratory to standardize strong base solutions. It has the unwieldy formula of KHC₈H₄O₄. This is often written in shorthand notation as KHP.
If 5.15 grams of KHP are needed to exactly neutralize 32.2 mL of a barium hydroxide solution, what is the concentration of the base solution?

ANSWER: ______ M barium hydroxide

Answer 1

To solve this question, first we need to write balance chemical reaction between KHP and Ba(OH)2 which is given by

2 KHC8H4O4 + Ba(OH)2 ---> Ba(KC8H4O4)2 + 2 H2O

Now find out the moles of KHP first.

5.15 g KHC8H4O4 * (1 mol KHC8H4O4/204.22 g KHC8H4O4) = 0.025217 mol KHC8H4O4

Now we need to find moles of Ba(OH)2. For this check mole to mole ratio for KHC8H4O4 to Ba(OH)2 which is 2:1.

2 mol KHC8H4O4 = 1 mol Ba(OH)2

0.025217 mol KHC8H4O4 = 0.025217 mol KHC8H4O4 * (1 mol Ba(OH)2/2 mol KHC8H4O4) = 0.0126085 mol Ba(OH)2

Now we have moles of Ba(OH)2 and its volume. To find molarity we use the formula

Molarity = moles/Litre of solution

First convert volume of Ba(OH)2 in litre

32.2 ml * (1L/1000 ml) = 0.0322 L

Molarity = 0.0126085 mol / 0.0322 L = 0.3915 mol/L or M.

Therefore molarity of Ba(OH)2 solution will be 0.392 M.

Thanks.