[dumbnoob1010]

I want to ask why the boiling point of SiO2 is smaller than that of SiC?

They both forms giant covalent network with Si tetrahedrally bonded to 4 O in the case of SiO2 and Si bonded tetrahedrally to 4 C in the case of SiC.
And I suppose a Si-C bond is weaker than Si-O bond because:
C has a larger covalent radius than O
=> bond length of Si-C > Si-O.
=> bond strength of Si-C < Si-O
So doesn't it make more sense the b.p. of SiO2 > SiC?

[AWK]

Look at wikipedia. Your consideration are rarther irrelevant because SiC sublimes .

[Immortal_FX127]

Maybe the structure of SiC network is more stable than SiO2 network. The former seems more symmetrical.

[dumbnoob1010]

Is it because in order to completely vaporize SiO2, only 2 Si-O bonds have to be broken per SiO2 molecule but 3 Si-C bonds have to be broken per SiC molecule?