Question

1. choose the best answer.

which type of reaction occurs when elemental hydrogen and oxygen come together to form water?
synthesis
replacement
decomposition
compound

1. choose all that apply.

$2\ce{naoh}(aq) + \ce{h2co3}(aq) \
ightarrow \ce{na2co3}(s) + 2\ce{h2o}(l)$
this reaction produced _____.
precipitate
gas
water

Explanation:

Question 5

Step1: Recall reaction types

Synthesis: \( A + B
ightarrow AB \); Replacement: \( A + BC
ightarrow AC + B \); Decomposition: \( AB
ightarrow A + B \); Compound is not a reaction type.

Step2: Analyze \( H_2 + O_2

ightarrow H_2O \)
Two elements combine to form a compound, matching synthesis.

Step1: Identify products

Products: \( \text{Na}_2\text{CO}_3(s) \) and \( \text{H}_2\text{O}(l) \).

Step2: Check each option

• Precipitate: \( \text{Na}_2\text{CO}_3 \) is solid (precipitate).
• Gas: No gas product.
• Water: \( \text{H}_2\text{O}(l) \) is water.

Answer:

A. synthesis

Question 6