Question

A precipitation reaction is caused by mixing 100. mL of 0.25 M K2Cr2O7 solution with 100. mL of 0.25 M Pb(NO3)2 solution. When the precipitate forms, it is filtered from the mixture.What is the concentration of nitrate anion in the reaction mixture after filtration?0.50 M0.10 M0.0 M0.25 M

Answer 1

Answer:

The molarity of the nitrate ion = 0.25 M

Explanation:

Step 1: Data given

Volume of 0.25 M K2Cr2O7 = 100 mL = 0.1 L

Volume of 0.25 M Pb(NO3)2 =100 mL = 0.1 L

Step 2: The balanced equation

Pb(NO3)2(aq) + K2Cr2O7(aq) → PbCr2O7(s) + 2KNO3(aq)

PbCr2O7(s) + 2KNO3(aq) → PbCr2O7(s) + 2K+ + 2NO3-

Step 3: Calculate moles of K2Cr2O7

Moles K2Cr2O7 = Molarity K2Cr2O7 * volume

Moles K2Cr2O7 = 0.25M * 0.1 L

Moles K2Cr2O7 = 0.025 moles

Step 4: Calculate moles of Pb(NO3)2

Moles Pb(NO3)2  = 0.25 M * 0.1 L

Moles Pb(NO3)2  = 0.025 moles

Step 5: Calculate limiting reactant

For 1 mol Pb(NO3)2 consumed, we need 1 mol of K2Cr2O7, to produce 1 mol of PbCr2O7 and 2 moles of KNO3

Both reactant will be completely consumed. since there will react 0.025 moles of both.

Step 6: Calculate moles of KNO3

For 1 mol Pb(NO3)2 consumed, we need 1 mol of K2Cr2O7, to produce 1 mol of PbCr2O7 and 2 moles of KNO3

For 0.025 mol Pb(NO3)2, we have 2*0.025 = 0.050 moles of KNO3

Step 7: Calculate moles of nitrate ion

2 moles KNO3 will dissociate in 2 moles of K+ and 2 moles of NO3-

For 0.050 moles KNO3, we'll have 0.050 moles of NO3-

Step 8: Calculate molarity of NO3- ion

Molarity NO3- = moles NO3- / volume

Molarity NO3- = 0.050 moles/ 0.2L

Molarity NO3- = 0.25 M

The molarity of the nitrate ion = 0.25 M