magnesium (24.30 g) reacts with hydrogen chloride (x g) to produce hydrogen gas (2.04 g) and magnesium…

Explanation:

Step1: Write the chemical reaction equation

$Mg + 2HCl=MgCl_{2}+H_{2}$

Step2: Calculate the moles of magnesium

The molar - mass of $Mg$ is $M_{Mg}=24.30\ g/mol$. The moles of $Mg$, $n_{Mg}=\frac{m_{Mg}}{M_{Mg}}=\frac{24.30\ g}{24.30\ g/mol}=1\ mol$.

Step3: Calculate the moles of hydrogen gas

The molar - mass of $H_{2}$ is $M_{H_{2}} = 2.04\ g/mol$. The moles of $H_{2}$, $n_{H_{2}}=\frac{m_{H_{2}}}{M_{H_{2}}}=\frac{2.04\ g}{2.04\ g/mol}=1\ mol$.

Step4: Calculate the moles of magnesium chloride

The molar - mass of $MgCl_{2}$ is $M_{MgCl_{2}}=96.90\ g/mol$. The moles of $MgCl_{2}$, $n_{MgCl_{2}}=\frac{m_{MgCl_{2}}}{M_{MgCl_{2}}}=\frac{96.90\ g}{96.90\ g/mol}=1\ mol$.

Step5: Use the mole - ratio from the balanced equation

From the balanced equation $Mg + 2HCl=MgCl_{2}+H_{2}$, the mole - ratio of $HCl$ to $Mg$ is $2:1$. Since $n_{Mg} = 1\ mol$, the moles of $HCl$ used, $n_{HCl}=2n_{Mg}=2\ mol$.

Step6: Calculate the mass of $HCl$

The molar - mass of $HCl$ is $M_{HCl}=1.01\ g/mol + 35.45\ g/mol=36.46\ g/mol$. The mass of $HCl$, $m_{HCl}=n_{HCl}\times M_{HCl}=2\ mol\times36.46\ g/mol = 72.92\ g$.

Answer:

$72.92$