The mass of oxygen gas which occupies 5.6 litres at STP could be

To solve this problem, we need to use the molar volume of a gas at STP (Standard Temperature and Pressure), which is 22.4 liters per mole.

Step 1: Identify the given volume and the molar volume at STP. Given volume = 5.6 liters Molar volume at STP = 22.4 liters/mole

Step 2: Calculate the number of moles of the gas. Number of moles = Given volume / Molar volume at STP Number of moles = 5.6 liters / 22.4 liters/mole = 0.25 moles

Step 3: Calculate the mass of the gas. We know that one mole of oxygen gas (O2) has a mass of 32 grams (from the periodic table: Oxygen has an atomic mass of 16, and since O2 has two oxygen atoms, its molar mass is 16*2 = 32 grams/mole).

Mass of the gas = Number of moles * Molar mass Mass of the gas = 0.25 moles * 32 grams/mole = 8 grams

So, the mass of oxygen gas which occupies 5.6 liters at STP is 8 grams.