Question

The chemical equation below shows the decomposition of nitrogen triiodide (NI3) into nitrogen (N2) and iodine (I2). 2NI3 mc030-1.jpg N2 + 3I2 The molar mass of I2 is 253.80 g/mol, and the molar mass of NI3 is 394.71 g/mol. How many moles of I2 will form 3.58 g of NI3?
A) 0.00907
B) 0.00940
C) 0.0136
D) 0.0212

Answer 1

The balanced chemical reaction would be:

2NI3 = N2 + 3I2 

We use the reaction above and the molar masses of the substances involved. We start with the initial amount of NI3 reactant. 

3.58 g NI3 (1 mol NI3 / 394.71 g NI3) (3 mol I2 / 2 mol NI3) = 0.0136 mol I2

Therefore, option C is the answer.

Answer 2

The moles of I2 that will  form 3.85 g of NI3  is 0.0136  moles ( answer c)

   calculation

 2 NI3 → N2  + 3 I2

Step 1: calculate  the moles of NI3  that decomposes

 moles= mass/molar mass

=3.58 g/ 394.71 g/mol = 0.00907 moles

Step 2 :  use the mole ratio of NI3  to I 2  which is 2:3 to  calculate the moles of I2

 = 0.00907  x3/2  =0.0136  moles  ( answer C)