Hydrogen

To determine how many molecules of hydrogen are present in of hydrogen, we need to use the concept of molar mass and Avogadro's number.

1. Understanding the Molar Mass of Hydrogen:
The molecular formula for hydrogen gas is . The atomic mass of hydrogen ( ) is approximately (atomic mass unit). Therefore, the molar mass of is:

$ n 10 \, \text{g} \text{H}_2 2 \, \text{g/mol} 1 \, \text{mole} 6.02 \times 10^{23} 5 \, \text{moles} \text{H}_2 10 \, \text{g} 3.01 \times 10^{24} {3.01 \times 10^{24} \, \text{molecules}} $

To determine the molar ratio of hydrogen and oxygen in the formation of water, we need to analyze the chemical reaction involved.

1. Understanding the Reaction:
The formation of water involves the combination of hydrogen gas ( ) and oxygen gas ( ). The balanced chemical equation for this reaction is:

$ \text{H}_2 \text{O}_2 \text{H}_2\text{O} \text{H}_2 \text{O}_2 2 : 1 1 : 2 \text{H}_2 \text{O}_2 2 : 1 1 : 1 \text{H}_2 \text{O}_2 2 : 3 {2 : 1} $