# How do you balance this equation: ?Zn + ?H_2SO_4 -> ?ZnSO_4 + H_2

Jan 9, 2017

${\text{Zn" + "H"_2"SO"_4 → "ZnSO"_4 +"H}}_{2}$

#### Explanation:

You follow a systematic procedure to balance the equation.

${\text{Zn" + "H"_2"SO"_4 → "ZnSO"_4 +"H}}_{2}$

A method that often works is first to balance everything other than $\text{O}$ and $\text{H}$, then balance $\text{O}$, and finally balance $\text{H}$.

Another useful procedure is to start with what looks like the most complicated formula.

The most complicated formula looks like ${\text{ZnSO}}_{4}$. We put a 1 in front of it to remind ourselves that the number is now fixed.

${\text{Zn" + "H"_2"SO"_4 → color(red)(1)"ZnSO"_4 +"H}}_{2}$

Balance $\text{Zn}$:

We have $\text{1 Zn}$ on the right, so we need $\text{1 Zn}$ on the left. We put a 1 in front of the $\text{Zn}$.

$\textcolor{b l u e}{1} {\text{Zn" + "H"_2"SO"_4 → color(red)(1)"ZnSO"_4 +"H}}_{2}$

Balance $\text{S}$:

We have fixed $\text{1 S}$ on the right. We need $\text{1 S}$ on the left. Put a 1 in front of ${\text{H"_2"SO}}_{4}$.

$\textcolor{b l u e}{1} {\text{Zn" + color(orange)(1)"H"_2"SO"_4 → color(red)(1)"ZnSO"_4 +"H}}_{2}$

Balance $\text{O}$:

Done.

Balance $\text{H}$:

We have fixed $\text{2 H}$ on the left, so we need $\text{2 H}$ on the right. Put a 1 in front of ${\text{H}}_{2}$.

$\textcolor{b l u e}{1} {\text{Zn" + color(orange)(1)"H"_2"SO"_4 → color(red)(1)"ZnSO"_4 + color(purple)(1)"H}}_{2}$

Every formula now has a coefficient. We should have a balanced equation.

Let's check.

$\boldsymbol{\text{Atom" color(white)(m)"lhs"color(white)(m)"rhs}}$
$\textcolor{w h i t e}{m} \text{Zn} \textcolor{w h i t e}{m m l} 1 \textcolor{w h i t e}{m m l} 1$
$\textcolor{w h i t e}{m} \text{H} \textcolor{w h i t e}{m m l l} 2 \textcolor{w h i t e}{m m l} 2$
$\textcolor{w h i t e}{m} \text{S} \textcolor{w h i t e}{m m m} 1 \textcolor{w h i t e}{m m l} 1$
$\textcolor{w h i t e}{m} \text{O} \textcolor{w h i t e}{m m l l} 4 \textcolor{w h i t e}{m m l} 4$

All atoms balance. The balanced equation is

${\text{Zn" + "H"_2"SO"_4 →"ZnSO"_4 + "H"_2"SO}}_{4}$