Determine the percentage composition (by mass) of oxygen in NH4NO3.

60%

Explanation:

M(NH4NO3) = 2*14 +4*1 +3*16 = 80 g/mol

M(3O) = 3*16 = 48 g/mol

(48/80) *100 % =60% oxygen by mass.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

(b) which contains higher levels of vitamin b, oranges or spinach?

explanation:

you can eliminate a, c, and d because they are questions based on opinions.