Will FeS precipitate in a solution that is 0.10 M in Fe(NO3)2, 0.4 M in HCl, and 0.10 M in H2S? Will FeS precipitate if the pH of the solution is adjusted to pH 8 with an NH4+ - NH3 buffer? Kspa = 6 x 10^2 for FeS.

Video transcript

Hello. In this problem we are told the solution is created by mixing. Point to Mueller nickel acetate 0.0.3 Mueller nitric acid and point to Mueller hydro sulfuric acid. Under scenario one we want to know well nickel sulfide precipitate out of solution. Were given this liability product constant under acidic conditions for nickel sulfide. As 3.2 under scenario two, we want to know if the ph of the solution is increased to seven. Using a phosphate buffer. Will nickel to sulfide precipitate out of solution. So let's begin by writing the reaction for the scalability of nickel to sulfide in acid and then write the corresponding liability product constant expression. So we have nickel to sulfide and reacts with acid form Nicole Lyons, hydro sulfuric acid and water. So the scalability protocols that expression. Then under these acidic conditions we have concentration of nickel ions times the concentration of hydro sulfuric acid. The water is eliminated since it's a pure liquid. All over the concentration of our hydrogen minds squared. The nickel sulfide is parasol. So it's eliminated from South Delhi product cost expression. So then step two, we're going to address the first scenario. So we're going to calculate the reaction quotient Nickel concentration, then we have 0.20 moles of nickel to acetate. Every leader, one more of nickel to acetate. Then we'll produce one more nick alliance, our moles and nickel to as state cancels And our concentration of Nicole Lyons is 0.20 moller Our concentration of hydro spherical acid has given in the problem statement 0.20 moller. And the concentration of our hydrating minds comes from the concentration of nitric acid call that nitric acid is a strong acid, so it will dissociate completely to form hydrogen mines and nitrate anons. So in this case we have 0.30 moles nitric acid. Every leader and one more nitric acid Will produce one more of hydrogen mines And our moles of nitric gas cancels. So our concentration of hydrogen mines is 0.30 moller. So our reaction quotient too, then Is equal to the concentration of our Nick Alliance .2. This concentration of hydro spherical acid, which is also point to solar over the concentration of our hydrogen mines which is .3 fuller. And that's squared. So this works out to 0.4444. This is less than 3.2 which is equal to our solid ability product constant. And so that means that no equal to sulfide will precipitate, given that our reaction quotient Q is less than our solid ability product constant. It indicates the reaction favors the four direction to reach equilibrium which is away from the formation of the precipitate. Step three. Then we'll consider the second scenario and find our reaction quotient. So the concentration of our nick alliance remains the same concentration of our sulfuric acid also remains the same. We are now told that the P. H. S. Seven. So our hydrogen ion concentration is equal 10 to the minus ph So that's 10 to the minus seven. We have one times 10 to the -7 moller is our concentration of hydrogen mines. Our reaction quotient then is equal to the concentration of nickel ions that of Hydrofluoric acid over the concentration of our I do any wines And that's where this works out to 4.0 times 10 to the 12, Which is greater than 3.2, which is our scalability product constant. So that means nickel sulfide will precipitate. In this case, our reaction quotient Q is greater than our scalability product constant. That says reaction favors the reverse direction, which is towards the precipitate in order to reach equilibrium. So, in our first scenario, no nickel to sulfide will precipitate. Under our second scenario, nickel to sulfide will precipitate. And that's because our reaction quotient is greater than our solid ability product constant. And this corresponds to answer a thanks for watching. Hope this helps