Question

A student performs an experiment to determine the volume of hydrogen gas produced when a given mass of magnesium reacts with excess HCl(aq) , as represented by the net ionic equation above. The student begins with a 0.0360 g sample of pure magnesium and a solution of 2.0 M HCl(aq).

(a) Calculate the number of moles of magnesium in the 0.0360 g sample

Answer 1

Answer:

1.48x10⁻³ mol

Explanation:

The balanced equation is

Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)

The aqueous solution will disociate, so:

Mg(s) + 2H⁺(aq) + 2Cl⁻(aq) → Mg²⁺(aq) + 2Cl⁻(aq) + H₂(g)

Simplifying by eliminating the bolded substances that have the same amount in both sides, we have the net ionic equation:

Mg(s) + 2H⁺(aq) → Mg²⁺(aq) + H₂(g).

a) The number of moles of Magnesium is the mass divided by the molar mass (24.305 g/mol):

n = 0.0360/24.305

n = 1.48x10⁻³ mol