Question

The equation for water is H
2
​
+O
2
​
→H
2
​
O. To balance the equation, which coefficient should be placed in front of H
2
​
and H
2
​
O?

1. 1
2. 2
3. 3
4. 4

Answer 1

To balance the equation for the formation of water, \( \text{H}_2 + \text{O}_2 \rightarrow \text{H}_2\text{O} \), we need to ensure that the number of atoms of each element is the same on both sides of the equation.

On the left side, there are:
- 2 hydrogen (H) atoms from \( \text{H}_2 \)
- 2 oxygen (O) atoms from \( \text{O}_2 \)

On the right side, there is:
- 2 hydrogen atoms from \( \text{H}_2\text{O} \)
- 1 oxygen atom from \( \text{H}_2\text{O} \)

To balance the equation, we can place a coefficient of 2 in front of \( \text{H}_2\text{O} \) on the right side:

\[
\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}
\]

Now the equation becomes:
- Left side: 2 H and 2 O
- Right side: 4 H (from \( 2\text{H}_2\text{O} \)) and 2 O

To balance the hydrogen, we need to place a coefficient of 2 in front of \( \text{H}_2 \):

\[
2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}
\]

Now both sides have:
- 4 hydrogen atoms
- 2 oxygen atoms

Thus, the balanced equation is:

\[
2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}
\]

So, the coefficient that should be placed in front of \( \text{H}_2 \) is **2** and in front of \( \text{H}_2\text{O} \) is also **2**.

Therefore, the answer to the question is:
**2** (for both \( \text{H}_2 \) and \( \text{H}_2\text{O} \)).