Question

balance the following chemical equation CU + HNO3 gives NO2 + H2O + Cu(NO3) 2​

Answer 1

skeletal equation: Cu + HNO₃-----> NO₂ + H₂O + Cu(NO₃)₂

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

An easier way to balance complex equations:

Step 1 : Assign variables to each compound in the equation:

Cu = a

HNO₃ = b

NO₂ = c

H₂O = d

Cu(NO₃)₂ = e

Step 2 : Now equate each variables according to their substituent elements in LHS and RHS

FOr ex: There is 1 Cu in LHS as well as in RHS,

So, a = e

There is 1 H in LHS and 2 H in RHS,

So, b = 2d

There is 1 N in LHS and 1+2 N in RHS

So, b = c+2e

There is 3 O in LHS and 2+1+6 O in RHS

3b = 2c + d + 6e

So, the equations we've got is

a = e-------(1)

b = 2d-----------(2)

b = c+2e----------------(3)

3b = 2c + d + 6e------------------(4)

Step 3 : Now solve for a,b,c,d and e

Let a = 1

So, e = 1 (because of 1)

So, in (3) ; b = c+2

c = b-2

So in (2); d = b/2

So, in (4) ; 3b = 2(b-2) + b/2 + 6

3b = 2b - 4 + b/2 + 6

6b = 4b - 8 + b+ 12

b = 4

Therefore we got, a =1

b = 4

c= 2

d = 2

e =1

Hence the balanced equations looks like;

1Cu + 4HNO₃-----> 2NO₂ + 2H₂O + 1Cu(NO₃)₂