Question

balancing chemical equations
cynthia wilson
c₃h₈ + 5o₂ → 3co₂ + 4h₂o
3 carbons
8 hydrogens
10 oxygens
3 carbons
8 hydrogens
10 oxygens
multiple - choice question
how do you know when your reaction is balanced?
it has the same type of elements.
it has the same number of atoms of a given element.
rewatch

Explanation:

A balanced chemical equation must have the same number of atoms of each element on both sides of the equation. The type of elements is always the same in a chemical reaction (as per the law of conservation of mass), but that alone does not mean the equation is balanced. For example, in the given reaction \(C_3H_8 + 5O_2
ightarrow3CO_2 + 4H_2O\), we check the number of carbon (\(C\)) atoms: \(3\) on the left (\(C_3H_8\)) and \(3\) on the right (\(3CO_2\)). Hydrogen (\(H\)) atoms: \(8\) on the left (\(C_3H_8\)) and \(4\times2 = 8\) on the right (\(4H_2O\)). Oxygen (\(O\)) atoms: \(5\times2=10\) on the left (\(5O_2\)) and \((3\times2)+(4\times1)=6 + 4=10\) on the right (\(3CO_2+4H_2O\)). So, it's the equality of the number of atoms of each element that determines a balanced equation.

Answer:

It has the same number of atoms of a given element.