Gas laws question

Question

A 7.50 g sample of lithium metal is dropped into 25.0 mL of 1.5 M hydrochloric acid. What volume of hydrogen gas would be evolved once the limiting reactant has been consumed? (The reaction is performed at 298 K and 1 atm)

Answer 1

Write the balanced equation for the reaction:

2Li + 2HCl ==> 2LiCl + H₂(g) 

Find limiting reactant:

moles Li = 7.50 g x 1 mole/6.94 g = 1.08 moles Li

moles HCl = 0.025 L x 1.5 moles/L = 0.0375 moles HCl

Since mole ratio of Li to HCl is 1:1 in the balanced equation, HCl IS LIMITING.

Calculate moles H₂ gas produced from 0.0375 moles HCl:

0.0375 moles HCl x 1 moles H₂(g)/2 moles HCl = 0.01875 moles H₂(g)

Convert moles H₂(g) to volume using the ideal gas law: PV = nRT and solve for V

V = nRT/P = (0.01875)(0.0821)(298)/1 = 0.459 liters