Question

What volume of 0.125 M H₂SO₄ is required to neutralize 2.50 g of Ca(OH)₂?

**** I know the answer is 270 mL, but I do not understand how to work it. Please explain where each number comes from that is used to get this answer. I'm very lost. Thank you!!

Answer 1

we have the Balanced chemical equation as:

H2SO4 + Ca(OH)2 ---> CaSO4 + 2 H2O

Molar mass of Ca(OH)2 = 1*MM(Ca) + 2*MM(O) + 2*MM(H)

= 1*40.08 + 2*16.0 + 2*1.008

= 74.096 g/mol

mass of Ca(OH)2 = 2.5 g

we have below equation to be used:

number of mol of Ca(OH)2,

n = mass of Ca(OH)2/molar mass of Ca(OH)2

=(2.5 g)/(74.096 g/mol)

= 3.374*10^-2 mol

From balanced chemical reaction, we see that

when 1 mol of Ca(OH)2 reacts, 1 mol of Ca(OH)2 reacts

mol of Ca(OH)2 reacted = (1/1)* moles of Ca(OH)2

= (1/1)*3.374*10^-2

= 3.374*10^-2 mol

This is number of moles of H2SO4

we have below equation to be used:

M = number of mol / volume in L

0.125 = 3.374*10^-2/ volume in L

volume = 0.26992 L

volume = 270 mL

Answer: 270 mL