Either my online portal hates me, or I don't understand how to balance properly.
QUESTION
Balance reaction of arsenic(III) sulfide with nitric acid As2S3(s) + NO3-(aq) → H3AsO4(aq) + S(s) + NO(g)
Is this the correct balanced equation?
32 H2O + 24 As2S3(s) + 80 H+(aq) + 80 NO3-(aq) → 48 H3AsO4(aq) + 9 S8(s) + 80 NO(g)
If yes, which is the oxidizing reagent and what is the reducing reagent?
oxidn is loss of electrons.
It is reduced.
Reduction is gain of electrons. It is the oxidizing agent. Isn't that NO3^-?
The equation looks balanced to me; one never knows these days if S8 or S is required.
To determine if the given balanced equation is correct, we need to examine the balanced coefficients for each compound on both sides of the equation and check if they are consistent with the law of conservation of mass.
First, let's tally up the atoms on both sides of the equation:
Left side:
- Arsenic (As): 4 atoms (2 As2S3)
- Sulfur (S): 3 atoms (3 S)
- Nitrogen (N): 80 atoms (80 NO3-)
- Hydrogen (H): 80 atoms (80 H+)
- Oxygen (O): 48 atoms (48 O from H3AsO4)
Right side:
- Arsenic (As): 6 atoms (6 As from H3AsO4)
- Sulfur (S): 8 atoms (1 S8)
- Nitrogen (N): 80 atoms (80 NO)
- Hydrogen (H): 32 atoms (32 H2O)
- Oxygen (O): 128 atoms (48 from H3AsO4 and 80 from NO and H2O)
Comparing the atom counts, we can see that there is a discrepancy for the oxygen atoms. On the left side, we have 48 O atoms, while on the right side, there are 128 O atoms. This means the given balanced equation is not correct.
To balance the equation, we need to adjust the coefficients until the number of atoms on both sides is equal. Here is the correctly balanced equation:
8 As2S3(s) + 91 HNO3(aq) → 12 H3AsO4(aq) + 8 S(s) + 91 NO(g) + 32 H2O(l)
Now, moving on to your second question, let's determine the oxidizing and reducing agents in the balanced equation.
In this reaction, the substance that is being reduced is the one that gains electrons, while the substance that is being oxidized is the one that loses electrons. To identify the oxidizing and reducing agents, we must look at the changes in oxidation states of the elements.
In the given reaction:
- Arsenic (As) is oxidized from an oxidation state of +3 in As2S3 to +5 in H3AsO4.
- Nitrogen (N) is reduced from an oxidation state of +5 in NO3- to +2 in NO.
Therefore, the reducing agent is NO3- (nitrate ion) since it causes the reduction of nitrogen from +5 to +2. And the oxidizing agent is As2S3 (arsenic(III) sulfide) as it undergoes oxidation by increasing the oxidation state of arsenic from +3 to +5.
Remember that the oxidizing agent itself gets reduced while causing another substance to be oxidized, and the reducing agent itself gets oxidized while causing another substance to be reduced.