Question 8 (2 points)
Use the law of conservation of mass to solve the problem below for the missing mass of a product.
In the above reaction, 45.3 grams of Zinc (Zn) reacts completely with 72.4 grams of Hydrochloric acid (HCl) to produce 68.7 grams of Zinc (II) chloride (ZnCl2) and ______ grams of Hydrogen gas (H2).
If you are unsure how to work out this problem, see a similar example linked HERE.
a
186.4 grams of H2
b
49 grams of H2
c
117.7 grams of H2
d
3.7 grams of H2
Let's first calculate the molar mass of each substance involved in the reaction:
Molar mass of Zn = 65.38 g/mol
Molar mass of HCl = 36.46 g/mol
Molar mass of ZnCl2 = 136.29 g/mol
Molar mass of H2 = 2.02 g/mol
Next, let's calculate the number of moles of each substance:
Number of moles of Zn = 45.3 g / 65.38 g/mol = 0.693 moles
Number of moles of HCl = 72.4 g / 36.46 g/mol = 1.987 moles
From the balanced chemical equation, we can see that one mole of Zn reacts with 2 moles of HCl to produce 1 mole of ZnCl2 and 1 mole of H2. Therefore, the limiting reactant is Zn.
Number of moles of ZnCl2 produced = 0.693 moles
Number of moles of H2 produced = 0.693 moles
Now, let's calculate the mass of H2 produced:
Mass of H2 = number of moles of H2 * molar mass of H2
Mass of H2 = 0.693 moles * 2.02 g/mol = 1.39986 ~ 1.4 grams
Therefore, the missing mass of Hydrogen gas produced is approximately 1.4 grams.
Correct answer: a
186.4 grams of H2