What is the mass of oxygen required to react completely with 15g of H2 gas to form water?

Sure, let's solve this step by step.

1. First, we need to know the balanced chemical equation for the reaction. The reaction of hydrogen with oxygen to form water is: 2H2 + O2 -> 2H2O

2. Next, we need to find the molar mass of H2 and O2. The molar mass of H2 is approximately 2 g/mol and the molar mass of O2 is approximately 32 g/mol.

3. Now, we can find the number of moles of H2 in 15g. Using the formula: moles = mass/molar mass, we get: moles of H2 = 15g / 2 g/mol = 7.5 moles.

4. From the balanced chemical equation, we know that the mole ratio of H2 to O2 is 2:1. Therefore, to react completely with 7.5 moles of H2, we need 7.5/2 = 3.75 moles of O2.

5. Finally, we can find the mass of O2 required using the formula: mass = moles * molar mass. So, mass of O2 = 3.75 moles * 32 g/mol = 120g.

Therefore, 120g of oxygen is required to react completely with 15g of H2 gas to form water.