D
If an element doesn’t have a number next to it that means there is only one. There a 4 hydrogens because the number is attached to the hydrogen atom. If there were 4 NH molecules the NH would be in parentheses and the 4 would be outside. Same goes for the oxygen atom and CO3 molecule.
The mass percent of sulfurous acid in the new solution : 38.9%
<h3>Further explanation</h3>
<em>In a container you have 800 g of a 35% by mass solution of sulfurous acid, from which 80 ml of water evaporates. What is the mass percent of sulfurous acid in the new solution? data: density of water is 1g / ml.</em>
<em />
solution 1
composition :


solution 2(new solution)
composition :

- Total mass of new solution after water evaporated

- %mass of acid in a new solution

Answer:
3Cu(NO3)2 + 2Al —> 2Al(NO3)3 + 3Cu
Explanation:
From the question given above,
Copper (II) nitrate reacts with aluminum to form aluminum nitrate and copper. This can be obtained represent as follow:
Cu(NO3)2 + Al —> Al(NO3)3 + Cu
Thus, we can balance the above equation as follow:
Cu(NO3)2 + Al —> Al(NO3)3 + Cu
There are 2 atoms of N on the left side and 3 atoms on the right side. It can be balance by putting 3 in front of Cu(NO3)2 and 2 in front of Al(NO3)3 as shown below:
3Cu(NO3)2 + Al —> 2Al(NO3)3 + Cu
There are 3 atoms of Cu on the left side and 1 atom on the right side. It can be balance by putting 3 in front Cu as shown below:
3Cu(NO3)2 + Al —> 2Al(NO3)3 + 3Cu
There are 2 atoms of Al on the right side and 1 atom on the left side. It can be balance by putting 2 in front of Al as shown below:
3Cu(NO3)2 + 2Al —> 2Al(NO3)3 + 3Cu
Thus, the equation is balanced.
The chemical formula of Iron (III) Sulfide is FeSO3. This element or compound has another name which is <span>ferric sulfide or sesquisulfide.</span>