Question

How many mL of 0.200 M HBr acid would be needed to neutralize 50.0 grams of calcium hydroxide solid that is completely dissolved in enough water to make 500. mL of solution?

Answer 1

Ca(OH)₂  Molar mass: 74.09 g/mol

Ca(OH)₂   Ca²⁺  + 2OH^-

So, 74.09 g of Ca(OH)₂ = 1 mole

50 gm of Ca(OH)₂ = (1 x 50) / 74.09 moles = 0.67 moles

Hence, 0.67 moles of Ca(OH)₂ in 500 mL.

But 2 moles of HBr neutralizes 1 moles of Ca(OH)₂.

So, 1.34 moles of HBr is will neutralize 0.67 moles of Ca(OH)₂.

Now,

[HBr] = 0.2 M, that is

0.2 moles in 1000 mL

1.34 moles in (1000 x 1.34) /0.2 mL

1.34 moles in 6700 mL.

So, 6700 mL HBr is required.