Answer to Question #161310 in General Chemistry for Faith

Question

Goal: Identify a limiting reactant

1. Count: H2O is the chemical formula for water. In order to produce a single molecule of 

water, how many hydrogen atoms are needed?

2

Oxygen atoms?

1. Predict: Set the number of O2 molecules to five and the number of H2 molecules to eight.

1. How many oxygen atoms are present?

Hydrogen atoms?

1. How many water molecules could form from these reactants?

1. After the molecules react, which reactant will be left over?

1. Which reactant will be the limiting reactant?

1. Click Play and wait until Reaction complete is shown. What happened?

1. Test: Click Reset. Set the number of O2 molecules to 10. 
2. How many hydrogen molecules (H2) will be needed for there to be no excess 

reactants?

7

Use the slider to set the number of H2 molecules to this value.

1. How many water molecules will be formed?

1. Click Play. What happened?

1. Challenge yourself: Run the Gizmo with five O2 molecules and nine H2 molecules. 

1. How many of each molecule do you think will be produced by this reaction? 

O2:

H2:

H2O:

1. Click Play. How many were actually produced? O2:

H2:

H2O:

1. How do you explain this result? 

Activity B: 

Methane reaction

Get the Gizmo ready: 

• Select C + H2 becomes CH4.

Goal: Predict the results of a chemical reaction.

1. Count: CH4 is the chemical formula for methane. In order to produce a single molecule of 

methane, how many carbon (C) atoms are needed? 

Hydrogen atoms?

1. Predict: Set the number of C atoms to 14 and the number of H2 molecules to 10.
2. How many total hydrogen atoms are there?

1. How many methane molecules could form from these reactants?

1. After the atoms react, which reactant will be left over?

1. Which reactant will be the limiting reactant?

1. Click Play and wait until Reaction complete is shown. What happened?

1. Test: Click Reset. Set the number of C atoms to seven. 

1. How many hydrogen molecules (H2) will be needed for there to be no excess 

reactants?

Use the slider to set the number of H2 molecules to this value.

1. How many methane molecules will be formed?

7

1. Click Play. What happened? 

Answer 1

To find out what water is made of, it helps to look at its chemical formula, which is H2O. This basically tells us that the water molecule is composed of two elements: hydrogen and oxygen or, more precisely, two hydrogen atoms (H2) and one oxygen atom (O). Hydrogen and oxygen are gases at room temperature.

two atoms of hydrogen are needed to produce a single molecule of water. 

Chemical reaction: 2H₂ + O₂ → 2H₂O. /÷2.

H₂ + 1/2O₂ → H₂O.

Beside two atoms of hydrogen, there is also one atom of oxygen in a single molecule of water (H₂O). Atoms of hydrogen and oxygen are connected by polar covalent bonds.