ANS:A - 0.5

To determine the amount of hydrogen gas (𝐻2H2​) produced when 6 g of magnesium (Mg) reacts with excess acid, we need to first calculate the number of moles of magnesium and then use stoichiometry to find the number of moles of hydrogen gas produced.

1. Calculate the number of moles of magnesium: Number of moles of magnesium=Mass of magnesiumMolar mass of magnesiumNumber of moles of magnesium=Molar mass of magnesiumMass of magnesium​ =6 g24 g/mol=24g/mol6g​ =0.25 mol=0.25mol
2. From the balanced chemical equation for the reaction between magnesium and acid, we know that 1 mole of magnesium produces 1 mole of hydrogen gas: Mg+2HCl→MgCl2+H2Mg+2HCl→MgCl2​+H2​
3. Calculate the number of moles of hydrogen gas produced: Number of moles of hydrogen gas=Number of moles of magnesiumNumber of moles of hydrogen gas=Number of moles of magnesium =0.25 mol=0.25mol
4. Now, use the formula to calculate the mass of hydrogen gas produced: Mass of hydrogen gas=Number of moles×Molar mass of hydrogen gasMass of hydrogen gas=Number of moles×Molar mass of hydrogen gas =0.25 mol×2 g/mol=0.25mol×2g/mol =0.5 g=0.5g