Question

In the decomposition potassium nitride, 10.65 g of nitrogen form. How much potassium nitride was present initially ?

Answer 1

Answer:

Mass =  99.8 g  

Explanation:

Given data:

Mass of potassium nitride = ?

Mass of nitrogen produced = 10.65 g

Solution:

Chemical equation:

2K₃N→ 6K + N₂

Moles of nitrogen:

Number of moles = mass/ molar mass

Number of moles =  10.65 g / 28 g/mol

Number of moles = 0.38 mol

Now we will compare the moles of nitrogen with potassium nitride.

                        N₂              ;         K₃N

                         1               :            2

                         0.38          :          2×0.38 =0.76

Mass of potassium nitride:

Mass = molar mass × number of moles

Mass =    131.3 g/mol ×   0.76 mol

Mass =  99.8 g