Which of the following reactions is an example of a single replacement reaction? Select one:
a. H2 + O2 --> H2O
b. CH4 + O2 --> CO2 + H2O
c. NaI + Br2 --> NaBr + I2
d. H2CO3 --> H2O + CO2

C

Explanation:

Single replacement reactions is when only one element gets replaced / changed. This usually looks like this: A + BC = B + AC or A + BC = C + AB

Therefore, the number of reactants must be equal to the number of products, since no actual combinations / break ups are occurring.

Answers A and D are eliminated right away since the number of products don't equal the number of reactants.

Answer B is wrong because it does not show simply one element being replaced, instead, two compounds are being formed. It doesn't look like the example given.

Only answer C shows that one element is replaced:

The iodine is replaced with bromine to form NaBr + I2

it is the most commonly accepted one