1. A combination reaction may also be a displacement reaction.

Question

True or False

2. The combustion of an element is always a combination reaction.
True or False

For number 1, I first thought true, but then again, nothing is being displaced in a combination reaction, right? You are just combining, so that would make the statement false, correct?

For number 2, I'm thinking it is true since O2 is combined with the compound during combustion. Is this correct? I guess the "always" term is throwing me off in this true/false question.

Thank you!!

Answer 1

I agree with your thoughts about #1.
For #2, I would look at it this way. If C combines with O2 we get
C + O2 ==> CO2 and that is, indeed, a combination reaction. However, if we use a hydrocarbon, such as CH4 and combine that with O2 we get
CH4 + O2 ==> CO2 + H2O and that isn't a combination reaction. It is true that the C combines with O2 to form CO2 and the H combines with O2 to form H2O but that isn't what is meant by combination reactions so I think that "always" makes it false. I had some teachers when I was a student that told me to "always" put false when the question had "always" in it. :-) That's not "always" a true but it works most of the time.