Question

How many grams of phosphoric acid would be needed to neutralize 100g of magnesium hydroxide?(The molecular weights are $H_3{PO}_4=98andMg{\left(OH\right)}_2=58.3$)

• A. $112g$
• B. $252g$
• C. $66.7g$
• D. $168g$

Answer 1

The correct option is A $112g$

$3Mg(OH{)}_2+2H_{3}P{O}_4⟶M{g}_3(P{O}_4{)}_2+6H_{2}O$

$\Rightarrow \left(\frac{W}{E}\right)H_{3}P{O}_4=\left(\frac{W}{E}\right)Mg(OH{)}_2$

$\Rightarrow {\left(\frac{W}{98}\right)}^3=\left(\frac{100}{58}\right)\times 2$

$\Rightarrow W=\frac{100\times 98\times 2}{58\times 3}$

$\Rightarrow W=112g$

$\therefore 112g$ of $H_{3}P{O}_4$ is needed to neutralize $100g$ of $Mg(OH{)}_2$.