Question

this equation represents an unbalanced chemical reaction: al + o₂ → al₂o₃
when the equation is balanced, which coefficient should be placed before al₂o₃?
2
3
4
5
identify the type of reaction:
agno₃ + nacl → agcl + nano₃
synthesis
double replacement
decomposition
combustion

Explanation:

First Sub - Question (Balancing Chemical Equation)

Step 1: Analyze O atoms

The unbalanced equation is \( \text{Al}+\text{O}_2
ightarrow\text{Al}_2\text{O}_3 \). On the left, O is in \( \text{O}_2 \) (2 atoms), on the right, O is in \( \text{Al}_2\text{O}_3 \) (3 atoms). The least common multiple of 2 and 3 is 6. So, we put a coefficient of 3 in front of \( \text{O}_2 \) (to get 6 O atoms: \( 3\times2 = 6 \)) and a coefficient of 2 in front of \( \text{Al}_2\text{O}_3 \) (to get 6 O atoms: \( 2\times3=6 \)).

Step 2: Analyze Al atoms

After putting 2 in front of \( \text{Al}_2\text{O}_3 \), the number of Al atoms on the right is \( 2\times2 = 4 \). So we put a coefficient of 4 in front of Al on the left. The balanced equation is \( 4\text{Al}+3\text{O}_2
ightarrow2\text{Al}_2\text{O}_3 \). So the coefficient in front of \( \text{Al}_2\text{O}_3 \) is 2.

In the reaction \( \text{AgNO}_3+\text{NaCl}
ightarrow\text{AgCl}+\text{NaNO}_3 \), the cations (\( \text{Ag}^+ \) and \( \text{Na}^+ \)) and anions (\( \text{NO}_3^- \) and \( \text{Cl}^- \)) are exchanged between the two compounds. This fits the definition of a double - replacement reaction, where \( \text{AB}+\text{CD}
ightarrow\text{AD}+\text{CB} \) (here \( \text{AB}=\text{AgNO}_3 \), \( \text{CD}=\text{NaCl} \), \( \text{AD}=\text{AgCl} \), \( \text{CB}=\text{NaNO}_3 \)).

Answer:

2 (the option with "2")

Second Sub - Question (Identifying Reaction Type)