Question

1. a student combines 15 g of hydrogen gas with 120 g of oxygen gas inside a sealed container. a chemical reaction occurs, forming water. what is the mass of the water produced in the container? 105 g 120 g 135 g 150 g clear all

Explanation:

Step1: Write the chemical reaction

The reaction between hydrogen ($H_2$) and oxygen ($O_2$) to form water ($H_2O$) is $2H_2 + O_2=2H_2O$.

Step2: Determine the limiting - reactant

The molar mass of $H_2$ is $M_{H_2}=2\ g/mol$, so the number of moles of $H_2$, $n_{H_2}=\frac{15\ g}{2\ g/mol}=7.5\ mol$. The molar mass of $O_2$ is $M_{O_2} = 32\ g/mol$, so the number of moles of $O_2$, $n_{O_2}=\frac{120\ g}{32\ g/mol}=3.75\ mol$. From the balanced - equation, the mole ratio of $H_2$ to $O_2$ is $2:1$. For $3.75\ mol$ of $O_2$, the amount of $H_2$ required is $2\times3.75 = 7.5\ mol$. So, there is no limiting reactant.

Step3: Use the law of conservation of mass

According to the law of conservation of mass, the total mass of reactants equals the total mass of products in a chemical reaction. The total mass of reactants is $m = 15\ g+120\ g=135\ g$. So the mass of water produced is $135\ g$.

Answer:

135 g