Question

What is the number of moles and the mass of Mg required to react with 7.50g of HCl and produce MgCl2 and H2? 1.25 g 2.50 g 5.00 g

Answer 1

Answer:

The correct option is: 2.50 g

Explanation:

Reaction involved: Mg(s) + 2 HCl(aq) → MgCl₂(aq) + H₂(g)

Molar mass: Mg = 24.305 g/mol, HCl = 36.461 g/mol

In the given reaction, 1 mole Mg reacts with 2 moles HCl.

Given: mass of HCl = 7.50 g

So, the number of moles of HCl = given mass ÷ molar mass = 7.50 g ÷ 36.461 g/mol = 0.2057 moles

Therefore, the number of moles of Mg that reacts with 0.2057 mole HCl = 0.2057 ÷ 2 = 0.1028 moles

Therefore, the mass of Mg in grams = molar mass × number of moles = 24.305 g/mol × 0.1028 mole = 2.5 g