To determine which chemical equation is correctly balanced, we need to evaluate each equation by counting the number of atoms of each element on both sides of the arrow.
1. First equation:
[tex]\[
2 \text{Ca (s)} + \text{Cl}_2 \text{(g)} \rightarrow \text{CaCl}_2 \text{(s)}
\][/tex]
- Left side: 2 Ca, 2 Cl
- Right side: 1 Ca, 2 Cl
The left side has 2 calcium atoms and 2 chlorine atoms, while the right side has 1 calcium atom and 2 chlorine atoms. Therefore, this equation is not balanced.
2. Second equation:
[tex]\[
2 \text{Mg (s)} + \text{O}_2 \text{(g)} \rightarrow 2 \text{MgO (s)}
\][/tex]
- Left side: 2 Mg, 2 O
- Right side: 2 Mg, 2 O
The left side has 2 magnesium atoms and 2 oxygen atoms, and the right side also has 2 magnesium atoms and 2 oxygen atoms. Therefore, this equation is balanced.
3. Third equation:
[tex]\[
\text{Li (s)} + \text{Cl}_2 \text{(g)} \rightarrow 2 \text{LiCl (s)}
\][/tex]
- Left side: 1 Li, 2 Cl
- Right side: 2 Li, 2 Cl
The left side has 1 lithium atom and 2 chlorine atoms, while the right side has 2 lithium atoms and 2 chlorine atoms. Therefore, this equation is not balanced.
4. Fourth equation:
[tex]\[
2 \text{C (s)} + \text{O}_2 \text{(g)} \rightarrow \text{CO}_2 \text{(g)}
\][/tex]
- Left side: 2 C, 2 O
- Right side: 1 C, 2 O
The left side has 2 carbon atoms and 2 oxygen atoms, while the right side has 1 carbon atom and 2 oxygen atoms. Therefore, this equation is not balanced.
Based on the evaluation, the second chemical equation is correctly balanced. Therefore, the balanced equation is:
[tex]\[
2 \text{Mg (s)} + \text{O}_2 \text{(g)} \rightarrow 2 \text{MgO (s)}
\][/tex]
This corresponds to the second equation in the list. Hence, the correct answer is:
[tex]\[
\boxed{2}
\][/tex]
