Why Is HNO3 Split Up in the Reactants Side?

[r_swayze]

CuS precipitates dissolve in hot HNO3. The hot HNO3 oxidizes the sulfide ion in the precipitates to free elemental sulfur, forming NO(g) as its reduction product. For CuS,

3CuS(s) + 8H(aq) + 2NO3(aq) = 3Cu(aq) + 2NO(g) + 3S(s) + 4H2O(l)

I have a few questions here.
Why is HNO3 split up on the reactants side?
Does it matter what the coefficient is of CuS?
if so, how do know whether it 3 or 4 or 2?

 

[Borek]

First: there should be charges in the equation.

Second: nitric acid is dissociated in water solutions.

Third: do you know what it means "balanced reaction equation"?

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methods

 

[Blueshift5]

Great question! The HNO3 is split up on the reactants side because it is a strong acid and will dissociate in water to form H+ ions and NO3- ions. This is important because in order for the reaction to occur, the sulfide ions in the CuS precipitate need to be in contact with the H+ ions from the acid.

The coefficient of CuS does matter in this equation. The balanced equation shows that for every 3 moles of CuS, we need 8 moles of H+ ions and 2 moles of NO3- ions. This is because the reaction requires a certain ratio of reactants in order to proceed and produce the desired products. The coefficients are determined through a process called balancing equations, where we use the law of conservation of mass to ensure that the number of atoms of each element on both sides of the equation are equal.

To determine the coefficients, we start by balancing the elements that appear in the fewest number of compounds. In this case, it is Cu. We see that there are 3 Cu atoms on the reactants side and only 1 on the products side, so we need to multiply the Cu(aq) by 3 to balance it. This results in 3CuS(s) + 8H(aq) + 2NO3(aq) = 3Cu(aq) + 2NO(g) + 3S(s) + 4H2O(l). We then continue this process for each element until all elements are balanced.

I hope this helps to clarify the coefficients in the equation and how they are determined through balancing.