# Balancing chemical equation

does anyone know how to solve? i tried couple of times and had hard time with it. is there any trick we can use to do it quickly?

The equation for the preparation of nitrogen monoxide is:
a Cu + b HNO3 a Cu (NO3)2 + c H2O + 2NO
What is the value of b?

A 2
B 4
C 6
D 8
E 12
F 16

Hi.

Assuming you mistyped; instead of the second a it must be an arrow

The answer should be 4, in such questions you don’t have to work all the elements just the required ones.

2 Likes

I believe the answer is 4
If thats correct:
One easy way that i would solve the question would be like this
firstly start from the most rare element and big molecule, Which is Cu in Cu(No3)2,by attributing the number 1 to Cu(NO3)2 And calculating the number of Cu will see that we are going to need 1 CU in the left side, Then the 2nd most rare would be N in Cu(NO3)2 Which shows there are 2N In the right side plus 2N from 2NO, Altogether 4N In the right side, the same numer of N should be in the left side,taken together the number that should be attributed to HN03 is 4.

If there was any faster way,I’d be delighted to be informed

1 Like

b = 2 + 2a (based off \$2\$NO and \$a\$Cu)

b = c (based off hydrogen)

We can sub in the smallest number that gives us a whole number answer for a, b, c. This is a = 1 (notice that if make b or c = 1 then a will be 1/4. We want whole numbers when balancing equations so we would have to multiply everything by 4, giving us the same answer).

b = 2 + 2(1) (based off \$2\$NO and \$a\$Cu)
b=4
b = c = 4 (based off hydrogen)