Scientific Understanding

**What are chemical equation coefficients?**

Chemical equations also need to be balanced. The above chemical equations are not balanced. All further chemical equations on this page should be balanced (If they are not practice problems). This means they have to have the same amount of each element on the reactants side as they do on the products side. The trick to balancing is that you cannot change the compounds by changing the subscript. However, you can put a number in the front of them that is called the coefficient. In math terms, this coefficient multiplies all the elements of a single compound behind it. Before we start balancing equations let us try practicing using coefficients.

**Examples**: Label how many of each element is contained in the coefficient and compound combination.

2 NaCl | 2 Na and 2 Cl |

6 P_{4}S_{3} |
24 P and 18 S |

3 Mg_{3}(PO_{4})_{2} |
9 Mg, 6 P, and 24 O |

**VIDEO Coefficient Demonstrated Example 1**: Label how many of each element is contained in the coefficient and compound combination.

**4 CaBr _{2}**

**Step 1:**

What is the subscript of Ca?

Answer: 1

**Step 2:**

What is the coefficient of the compound?

Answer: 4

**Step 3:**

What is the coefficient multiplied by the subscript?

Answer: 4 * 1 = 4 So there are 4 Ca

**Step 4:**

What is the subscript of Br?

Answer: 2

**Step 5:**

What is the coefficient of the compound?

Answer: 4

**Step 6:**

What is the coefficient multiplied by the subscript?

Answer: 4 * 2 = 8 So there are 8 Br

**Step 7:**

What is the total of all the elements in the compound with the coefficient?

COMPLETE ANSWER: 4 Ca and 8 Br

**VIDEO Coefficient Demonstrated Example 2**:Label how many of each element is contained in the coefficient and compound combination.

**6 Al _{2}(CO_{3})_{3}**

**Step 1:**

What is the subscript of Al?

Answer: 2

**Step 2:**

What is the coefficient?

Answer: 6

**Step 3:**

What is the coefficient multiplied by the subscript of Al?

Answer: 6 * 2 = 12 So there are 12 Al

**Step 4:**

What is the subscript inside the parenthesis of C?

Answer: 1

**Step 5:**

What is the coefficient?

Answer: 6

**Step 6:**

What is the subscript outside the parenthesis?

Answer: 3

**Step 7:**

What is the subscript inside the parenthesis of C multiplied by the coefficient multiplied by the subscript outside the parenthesis?

Answer: 1 * 6 * 3 = 18 So there are 18 C

**Step 8:**

What is the subscript inside the parenthesis of O?

Answer: 3

**Step 9:**

What is the coefficient?

Answer: 6

**Step 10:**

What is the subscript outside the parenthesis?

Answer: 3

**Step 11:**

What is the subscript inside the parenthesis of O multiplied by the coefficient multiplied by the subscript outside the parenthesis?

Answer: 3 * 6 * 3 = 54 So there are 54 O

**Step 12:**

What is the total of all the elements in the compound with the coefficient?

COMPLETE ANSWER: 12 Al, 18 C, and 54 O

**PRACTICE PROBLEMS**: Label how many of each element is contained in the coefficient and compound combination.

5 Na_{2}S |
10 Na and 5 S |

2 Ni_{3}P |
6 Ni and 2 P |

4 Sr_{3}(PO_{3})_{2} |
12 Sr, 8P, and 24 O |

3 SiH_{4} |
3 Si and 12 H |

1 Se_{5}Br_{6} |
5 Se and 6 Br |

6 Be(NO_{3})_{2} |
6 Be, 12 N, and 36 O |