Question

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

Answer 1

According to mole concept and law of constant proportion

Answer 2

Hii dear,

When free oxygen reacts with hydrogen the reaction is as follows-

2H2 + O2 = 2H2O

2 moles of hydrogen + 1 mole of oxygen → 2 moles of water

1 moles of hydrogen reacts with 1/2 mole of oxygen gas

For H2

W1 = 15g

M1 = 2×1 = 2g

n1 = W1/M1 = 15/2 moles

For O2

n2 = 0.5 × 15/2 = 15/4 moles

M2 = 16×2 = 32g

W2 = n1×M1 = 15/4 × 32 = 120g

Theoretically, mass of oxygen reacted is 120 g.

Hope that helps...