Reaction 1: c3h8(g)+5o2(g)→3co2(g)+4h2o(g), δh1 = −2043 kj.
reaction 2: 3c3h8(g)+15o2(g)→9co2(g)+12h2o(g), δh2 = ?

determine the value of δh2.

From the given balanced chemical reactions, it may be observed that to obtain the second one, we just to multiply all the numerical coefficients of the first by 3. This implies that the value of ΔH2 is also thrice that of ΔH1. Therefore, the value of ΔH2 is -6129 kJ. 

C. which metal is less dense