What mass of zinc metal is required to evolve a 30*mL volume of dihydrogen gas from a 30*mL volume of hydrochloric acid at 1.00*mol*L^-1 concentration?

2 Answers
Mar 3, 2016

From the equation you can see that one mole of Zn will react with two moles of HCl.

Explanation:

Calculate the number of moles of HCl in 30mL of 1.00M solution, and divide by 2 for moles of Zn. Then multiply that by the molecular weight of Zn.

1M = 1mole/L 0.030L * 1mole/L = 0.030 moles HCl. 0.015 moles of Zn will react.

Mar 3, 2016

Nearly $1$ $\text{gram}$ zinc metal is required.

Explanation:

$Z n \left(s\right) + 2 H C l \left(a q\right) \rightarrow Z n C {l}_{2} \left(a q\right) + {H}_{2} \left(g\right) \uparrow$.

Each equiv of zinc metal requires 2 equiv of hydrochloric acid for complete oxidation. This gives this molar quantity: we simply take half of the molar quantity of hydrochloric acid used.

${n}_{H C l}$ $=$ $30 \times {10}^{-} 3 L \times 1.00 \cdot m o l \cdot {L}^{-} 1$ $=$ ??

${n}_{H C l}$ $=$ ${n}_{Z n} / 2$.

So the mass of zinc is simply:

$30 \times {10}^{-} 3 L \times 1.00 \cdot m o l \cdot {L}^{-} 1 \times \left(\text{1 equiv of zinc")/("2 equiv of acid}\right) \times 65.38 \cdot g \cdot m o {l}^{-} 1$ $=$ ??g