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.How many moles of solid product are formed?0.025 mol0.050 mol0.25 mol0.010 mol

Answer 1

Answer: The amount of solid product (lead dichromate) formed is 0.025 moles

Step-by-step explanation:

To calculate the number of moles for given molarity, we use the equation:

`\text{Molarity of the solution}=\frac{\text{Moles of solute}* 1000}{\text{Volume of solution (in mL)}}` .....(1)

• For potassium dichromate:

Molarity of potassium dichromate solution = 0.25 M

Volume of solution = 100.0 mL

Putting values in equation 1, we get:

`0.25M=\frac{\text{Moles of potassium dichromate}* 1000}{100.0}\\\\\text{Moles of potassium dichromate}=(0.25* 100)/(1000)=0.025mol`

• For lead nitrate:

Molarity of lead nitrate solution = 0.25 M

Volume of solution = 100.0 mL

Putting values in equation 1, we get:

`0.25M=\frac{\text{Moles of lead nitrate}* 1000}{100.0}\\\\\text{Moles of lead nitrate}=(0.25* 100)/(1000)=0.025mol`

The chemical equation for the reaction of potassium dichromate and lead nitrate follows:

`K_2Cr_2O_7(aq.)+Pb(NO_3)_2(aq.)\rightarrow PbCr_2O_7(s)+2KNO_3(aq.)`

The solid precipitate formed here is lead dichromate

By Stoichiometry of the reaction:

1 mole of lead nitrate produces 1 mole of lead dichromate

So, 0.025 moles of lead nitrate will produce =
`(1)/(1)* 0.025=0.025mol` of lead dichromate

Hence, the amount of solid product (lead dichromate) formed is 0.025 moles