Question

A) A compound of nitrogen and iodine is an extremely sensitive contact explosive that snaps and gives off a purple gas when a small crystal is touched lightly. A sample of this compound was analyzed to give 0.259 g nitrogen and 7.04 g iodine. What is the empirical formula of this compound? _______

B) The empirical formula of hydrazine is NH₂ and its molecular mass is 32.0. What is its molecular formula?
The molecular formula is ______

Answer 1

A)
we have mass of each elements as:
N: 0.259 g
I: 7.04 g


Divide by molar mass to get number of moles of each:
N: 0.259/14.01 = 0.018487
I: 7.04/126.9 = 0.055477


Divide by smallest to get simplest whole number ratio:
N: 0.018487/0.018487 = 1
I: 0.055477/0.018487 = 3




So empirical formula is:
NI3

B)

Molar mass of NH2,
MM = 1*MM(N) + 2*MM(H)
= 1*14.01 + 2*1.008
= 16.026 g/mol

Now we have:
Molar mass = 32.0 g/mol
Empirical formula mass = 16.026 g/mol
Multiplying factor = molar mass / empirical formula mass
= 32.0/16.026
= 2

Hence the molecular formula is : N2H4