Question

2h₂o₂(l)→2h₂o(l)+o₂(g)+heat
ammonium sulfate:
3(nh₄)₂so₄(s)+heat→6h₂o(g)+4nh₃(g)+n₂(g)+
3so₂(g)
ammonium dichromate:
(nh₄)₂cr₂o₇(s)+heat→n₂(g)+4h₂o(g)+cr₂o
whats common to all the reactions above?
select the best answer.
smoke is always a product.
a single starting compound breaks down into
other compounds.
two smaller molecules combine to make a
larger molecule.
heat is always produced in the reaction.

Explanation:

Let's analyze each option:

• Option 1: Smoke is not always a product. For example, in the decomposition of \(H_2O_2\), there is no smoke.
• Option 2: In the reaction \(2H_2O_2(l)\to2H_2O(l)+O_2(g)\), \(H_2O_2\) (a single - starting compound) breaks down. In \(3(NH_4)_2SO_4(s)+heat\to6H_2O(g)+4NH_3(g)+N_2(g)+3SO_2(g)\), \((NH_4)_2SO_4\) (a single - starting compound) breaks down. In \((NH_4)_2Cr_2O_7(s)+heat\to N_2(g)+4H_2O(g)+Cr_2O_3\), \((NH_4)_2Cr_2O_7\) (a single - starting compound) breaks down. This is a decomposition reaction where a single reactant breaks into multiple products.
• Option 3: The reactions shown are decomposition reactions (a single compound breaks down), not synthesis reactions (where two or more smaller molecules combine to form a larger one).
• Option 4: In the reaction \(2H_2O_2(l)\to2H_2O(l)+O_2(g)+heat\), heat is a product. But in \(3(NH_4)_2SO_4(s)+heat\to6H_2O(g)+4NH_3(g)+N_2(g)+3SO_2(g)\) and \((NH_4)_2Cr_2O_7(s)+heat\to N_2(g)+4H_2O(g)+Cr_2O_3\), heat is a reactant (input for the reaction to occur).

Answer:

A single starting compound breaks down into other compounds.