Question

potassium bromide KBr contains 32.9% by mss potassium . if 6.40 g of bromine reacts with 3.60g of potassium , calculate the number of moles of potassium which combine with bromine to KBr .

Answer 1

In 100 g KBr, K =32.9g, then Br=67.1g

2K+Br  

2

​  

→2KBr

MolesofBr

MolesofK

​  

=  

67.1/80

32.9/39

​  

=  

1

1.0057

​  

 

∴  

MolesofBr  

2

​  

 

MolesofK

​  

=  

1

1.0057×2

​  

=  

1

2.0114

​  

 

2K+Br  

2

​  

→2KBr

Given moles  

39

3.60

​  

               

160

6.40

​  

 

                   =0.092                             0.04

The reaction ratio for moles of K and Br  

2

​  

=2.0114. Thus, Br  

2

​  

 will be completely used leaving K.

∵   Moles of Br  

2

​  

 reacting =0.04

∴  Moles of K reacting =0.04×2.0114=8.01×10  

−2

mole