Question

What are the number of moles of hydrogen in NH4[Cr(SCN)4(NH3)2] if the weight of nitrogen in it is 49 grams?

(a) 3.5

(b) 5

(c) 7

(d) 10

I got this question in a national level competition.

Origin of the question is The Mole topic in section Moles, Density & Concentration of Basic Chemical Engineering

Answer 1

The correct choice is (b) 5

For explanation I would say: Moles of nitrogen = 49/14 = 3.5, => moles of  NH4[Cr(SCN)4(NH3)2] = 3.5/7 = 0.5, => moles of hydrogen = 0.5*10 = 5.