Question

A student dissolved 4.00 g of Co(NO_3)_2 in enough water to make 100.0 mL of stock solution. He took 4.00 mL of the stock solution and then diluted it with water to give 275 mL of a final solution. How many grams of NO^-_3 ion are there in the final solution?

Answer 1

400 8829 -0.219 b mo Concentrati on of the stock Co (NOz), solution, M1- Volume of the stock Co (NO3)2 solution , И-400 mL Volume of the dilute Co (NO3), soluti on, V-275 mL Concentrati on of the dilute C(N) olution, M2-? 0.100 L According to dilution principle, VM,-A4 Concentrati on of the dilute Co (NO3), soluti on, M2 (4.00 mL)(0.219 M) 275 mL 0.00318 M Equation representing the di ssociati on of Co (NOs) Co(NO3)2 (aq) Co2+ (aq) + 2NO3-(aq) Since 1 mol of Co(NO3)2 forms 2 mol of N03. LN03-J = 2[Co(NO3)2 -2(0.00318M) 0.00636 M 362.01g 1L0.00636 mol NO. 1000 mL Amount of NO3-= 275 mL × × 1L = 0.108 g