I want to create lots of gas very quickly from water to create a gas pressure gradient and I was thinking of Calcium carbonate (CaCO3). For example, CaCO3 to produce 20 L of carbon dioxide (CO2), CaCO3 (s) → CaO (s) + CO2 (g). Convert 20 L of CO2 to moles: Using the ideal gas law at STP (Standard Temperature and Pressure), 1 mole of any gas occupies 22.4 L. Moles of CO2 = 20 L ÷ 22.4 L/mol = 0.8929 mol

Mass of CaCO3 = 0.8929 mol * 100.09 g/mol = 89.37 g required to create 20L of CO2 gas.

Anyone has any suggestion of any other chemical compound to create more gas in a chemistry method?