Question

magnesium hydroxide, the active ingredient in milk of magnesia, neutralizes stomach acid, primarily hcl, according to the reaction mg(oh)₂(aq) + 2hcl(aq) → 2h₂o(l) + mgcl₂(aq). what mass of hcl, in grams, is neutralized by a dose of milk of magnesia containing 3.26 g of mg(oh)₂? express the mass in grams to three significant figures. mass of hcl = g

Explanation:

Step1: Calculate moles of $Mg(OH)_2$

The molar - mass of $Mg(OH)_2$ is $M_{Mg(OH)_2}=24.31+(2\times(16 + 1.01))=58.33\ g/mol$. The number of moles of $Mg(OH)_2$, $n_{Mg(OH)_2}=\frac{m_{Mg(OH)_2}}{M_{Mg(OH)_2}}$, where $m_{Mg(OH)_2} = 3.26\ g$. So, $n_{Mg(OH)_2}=\frac{3.26\ g}{58.33\ g/mol}=0.0559\ mol$.

Step2: Determine moles of $HCl$ using mole - ratio

From the balanced chemical equation $Mg(OH)_2(aq)+2HCl(aq)\to2H_2O(l)+MgCl_2(aq)$, the mole - ratio of $Mg(OH)_2$ to $HCl$ is $1:2$. So, $n_{HCl}=2\times n_{Mg(OH)_2}$. Substituting the value of $n_{Mg(OH)_2}$, we get $n_{HCl}=2\times0.0559\ mol = 0.1118\ mol$.

Step3: Calculate mass of $HCl$

The molar - mass of $HCl$ is $M_{HCl}=1.01 + 35.45=36.46\ g/mol$. The mass of $HCl$, $m_{HCl}=n_{HCl}\times M_{HCl}$. So, $m_{HCl}=0.1118\ mol\times36.46\ g/mol = 4.08\ g$.

Answer:

$4.08\ g$