Aluminum reacts with hydrochloric acid to produce aluminum chloride and hydrogen gas. What mass of hydrochloric acid reacts when 87.7 grams of aluminum dissolves in excess hydrochloric acid?
The correct answer and explanation is:
The balanced chemical reaction between aluminum and hydrochloric acid is:
2Al+6HCl→2AlCl3+3H22Al + 6HCl \rightarrow 2AlCl_3 + 3H_2
This shows that 2 moles of aluminum react with 6 moles of hydrochloric acid.
Step 1: Calculate moles of aluminum
The atomic mass of aluminum (Al) is approximately 27 g/mol. moles of Al=87.7 g27 g/mol=3.25 moles Al\text{moles of Al} = \frac{87.7 \text{ g}}{27 \text{ g/mol}} = 3.25 \text{ moles Al}
Step 2: Use stoichiometry to find moles of HCl needed
From the balanced equation, 2 moles of Al react with 6 moles of HCl.
So, moles of HCl=3.25×62=3.25×3=9.75 moles HCl\text{moles of HCl} = 3.25 \times \frac{6}{2} = 3.25 \times 3 = 9.75 \text{ moles HCl}
Step 3: Calculate the mass of hydrochloric acid
The molar mass of HCl is about 36.46 g/mol. mass of HCl=9.75 moles×36.46 g/mol=355.3 grams\text{mass of HCl} = 9.75 \text{ moles} \times 36.46 \text{ g/mol} = 355.3 \text{ grams}
Final answer:
355.3 grams of hydrochloric acid react with 87.7 grams of aluminum.
Explanation
In this chemical reaction, aluminum metal reacts with hydrochloric acid to form aluminum chloride and hydrogen gas. To find out how much hydrochloric acid is needed to completely react with a given mass of aluminum, the reaction must be balanced first. The balanced chemical equation provides the mole ratio between aluminum and hydrochloric acid.
Since the atomic mass of aluminum is 27 grams per mole, the given mass of aluminum (87.7 grams) can be converted to moles by dividing by 27. Next, using the mole ratio from the balanced equation, the moles of hydrochloric acid required are calculated. The ratio indicates that for every 2 moles of aluminum, 6 moles of hydrochloric acid are needed, which simplifies to 3 moles of HCl per mole of Al.
Finally, to find the mass of hydrochloric acid required, multiply the moles of HCl by its molar mass (36.46 g/mol). This process converts the amount from moles to grams, giving the mass of hydrochloric acid needed to react completely with 87.7 grams of aluminum.
This stoichiometric calculation is fundamental in chemistry to determine how much reactant is consumed or product is formed in a chemical reaction. It is useful in laboratory settings, industrial processes, and understanding reaction yields.