Question

How many grams of nitrogen dioxide may theoretically be produced when copper reacts completely with 21g of nitric acid?

Cu + 4HNO3 ---> Cu(NO3)2 + 2H2O + 2NO2

Answer 1

It says the answer is 7.7 g. I don't know how to get it though. Please guide me through.

Answer 2

see 4 moles of HNO3 reacting with Cu produces 2 moles of NO2
right

Answer 3

ya

Answer 4

can you tell molecular mass of HNO3 and NO2

Answer 5

63 and 46

Answer 6

So there is 1/3 mol of HN03

Answer 7

good :)
now i convert those moles to gram
using equation moles * molar mass =gram
that is 4*63 gram of HNO3 will give rise to 2*46 g of NO2
then 21 gram of HNO3 gives = 21*2*46 /4*63 = 7.66

Answer 8

that is 4*63g/mol gives rise to 2*46g/mol right?

Answer 9

@chmvijay

Answer 10

Yaaa that also u can doo :) since they have asked in grams i have initially only converted to gram u may also convert moles to gram also :)

Answer 11

So basically, here we have 4 mol * 63g/mol gives rise to 2 mol * 46g/mol.

The mols cancel out and u see that 252 g give rise to 92 g of NO2.

Since there is only 21 g of HNO3 then 252/x = 21 implies x = 12. Dividing 92/12 = 7.66666.

Correct?

@chmvijay

Answer 12

yaaa :)