Question

Calculate the amount of $Ca{\left(OH\right)}_2$ required to remove the hardness in $60$ litre of pond water containing $1.62mg$ of calcium bicarbonate per $100mL$ of water.

• A. $0.246g$
• B. $0.897g$
• C. $0.444g$
• D. $1.286g$

Answer 1

The correct option is C $0.444g$

$1.62$mg in $100$ml of water

So $60$ lit has $=0.9720g$ of ${Ca\left(H{CO}_3\right)}_2$

$=0.0060$ moles

${Ca\left({HCO}_3\right)}_2+Ca{\left(OH\right)}_2\to 2Ca{CO}_3+2H_{2}O$

$0.060\Rightarrow 0.0060$moles

$0.0060$ moles ${Ca\left(OH\right)}_2=0.444g$ of ${Ca\left(OH\right)}_2$