Sodiun reacts with water to give alkali solution and hydrogen gas.

a) construct a balance chenical reaction for the reaction

b) How many moles of sodiun metal react with water to make 45 dm3 of hydrogen gas and a sodiun hydroxide solution

a) 2Na + H_2O → 2NaOH + H_2; b) Moles of Na = 4.0 mol

b) Mass of Na

Step 1. Calculate the moles of hydrogen

I assume that the gas is at STP (1 bar and 0 °C). At STP, the molar volume of a gas is 22.71 dm^3.

Moles of H_2 = 45 dm^3 H_2 * (1 mol H_2/22.71 dm^3 H_2) = 1.98 mol H_2

Step 2. Calculate the moles of sodium

Moles of Na = 1.98 mol H_2 * 2 mol Na/1 mol H_2 = 4.0 mol Na