Question

A 1.04 g sample of KBr is dissolved in water to give 155 mL of solution. This solution is then added to 165 mL of 0.015 M aqueous Pb(NO3)2, in an attempt to remove the toxic lead(II) ions from the solution via precipitation as insoluble PbBr2(s).

The precipitation reaction that occurs is: Pb2+ (aq) + 2 Br (aq) ---> PbBr2 (s)

At the end of the reaction, what is the concentration (in molarity) of nitrate ions in the solution?

Note: potassium ions would be present, because both K+ and NO3- are spectator ions, but you have only been asked about the NO3-.

Question 4 Tries remaining: 1 Marked out of 4 p Flag question A 1.04 g sample of KBr is dissolved in water to give 155 mL of solution. This solution is then added to 165 mL of 0.015 M aqueous Pb(NO2), in an attempt to remove the toxic lead(II) ions from the solution via precipitation as insoluble PbBr_(s). The precipitation reaction that occurs is: Pb** (aq) + 2 Br (aq) --> PbBr,(s) At the end of the reaction, what is the concentration (in molarity) of nitrate ions in the solution? Note: potassium ions would also be present, because both K and No, are spectator ions, but you have only been asked about the NOZ: Select one: O a. 0.0300 mol/L O b. 0.00495 mol/L O c. 0.00773 mol/L O d. 0.0155 mol/L Check

Answer 1

The solution of question is not as trivial as the question itself.The solution just involves the calculation of Molarity of NO3- which involves the calculation of new molarity of aq lead(2) nitrate in increased volume of solution though the no of moles remain same.

(Pb(NO) Initially the molarity of solution is 0.015 and volume is 165 ml but when kB r solution is added the total volume becomes 220 me. Mo. of moles of Pb(NO2) = oo MX Vsan (inul - 0.015X.165 - 2.475 X 10-3 moles But the no. of moles does not change so now the molarity of Pb(NO3)₂ Ch combined solution is u m = n Vsoln (ini) 2.475X103 - 820x103 - M = 0.00773 molll for the reaction and removal of Pb(11) from ag Pb(NO3)2 , KBr is added precipitating Pb Br, but no concetto -ation does not change. Reaction for Pb(NO3)2 (ag.) is dissociation - Pb(NO₃), (ag.) - Pb2+ + 2NO 0.00773 2X0.00773 Initial 0:0@772 conc Final

or mall . The concentration of NO 2 - ů 2x0.0078 = 0.0155 M The correct option is d e d) 0.0155 molle