Question

What volume of 16M HNO3 is required to dissolve 0.50g of Cu metal? What volume is actually used? Why is there a difference?

Answer 1

Mass of Cu = 0.5 g

Molar mass of Cu = 63.5 g/mol

Moles of Cu = mass / molar mass =  0.5 g / 63.5 g/mol = 0.0078 mol

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

1 mol 4 mol

0.0078 mol ?

? = 0.0078 mol x 4 = 0.0312 mol of HNO3

Therefore,  0.0312 mol of HNO3 is required.

But we have , 16M HNO3.

molarity = moles / volume (in L)

volume (in L) = moles / molarity

Hence,

volume of HNO3 required = 0.0312 mol / 16 M

= 0.00195 L

= 1.95 mL

Therefore,

1.95 mL of 16 M HNO3 is required to dissolve 0.50g of Cu metal.