1. NaCl
2. CaO
3. KOH
4. MgS
5. CuCO3
6. Al2O3
7. Fe2O3
8. Na2CO3
9. AlHO3
10. (NH4)3N
11. Zn3N2
12. MgCO3
All numbers are subscripts.
This may help you
Use an arbitrary mass, 100 g is an easy number to work with.
60% of 100 g is 60 g, there are two A's. Each A is 30 g
40 g is B, and there is only one, so B is 40 g.
<span>A<span>B2</span></span>, would have a mass of 30 g + 2*40 g = 110 g
The new percent by mass composition of A is: <span><span><span>30g</span><span>110g</span></span>∗100%=27.3%</span>
The new percent by mass composition of B is: <span><span><span><span>80g</span><span>110g</span></span>∗100%=72.7%</span></span>