There will be a chemical reaction between the two solutions, resulting in the formation of insoluble lead chromate (PbCrO4) and soluble nitrate and sulphate ions. The balanced chemical equation for this reaction is:

Pb(NO3)2 + K2Cr2O7 → PbCrO4 + 2KNO3

However, the given concentrations of lead nitrate and chromic sulphate are not enough to completely react and form the maximum amount of lead chromate. To determine the amount of lead chromate formed and the remaining concentrations of the reactants, we need to calculate the limiting reagent and use stoichiometry.

First, we need to convert the volumes of the solutions to moles using the given molarities:

moles of Pb(NO3)2 = 0.15 M x 0.035 L = 0.00525 mol
moles of K2Cr2O7 = 0.12 M x 0.020 L = 0.0024 mol

Next, we can use the stoichiometric ratio between Pb(NO3)2 and K2Cr2O7 to determine which one is the limiting reagent:

1 mol Pb(NO3)2 : 1 mol K2Cr2O7

Since the amount of Pb(NO3)2 is greater than K2Cr2O7, Pb(NO3)2 is in excess and K2Cr2O7 is the limiting reagent. This means that all of the K2Cr2O7 will be consumed in the reaction and the amount of Pb(NO3)2 remaining will determine the amount of lead chromate formed.

Using the stoichiometric ratio between K2Cr2O7 and PbCrO4, we can calculate the theoretical yield of lead chromate:

1 mol K2Cr2O7 : 1 mol PbCrO4

moles of PbCrO4 = 0.0024 mol

Converting this to grams using the molar mass of PbCrO4 (323.2 g/mol):

mass of PbCrO4 = 0.0024 mol x 323.2 g/mol = 0.777 g

Therefore, the expected yield of lead chromate is 0.777 grams.

To calculate the concentrations of the remaining reactants, we need to use the volumes and moles of the reactants that were used:

moles of Pb(NO3)2 remaining = 0.00525 mol - 0.0024 mol = 0.00285 mol
moles of K2Cr2O7 consumed = 0.0024 mol

Using these values and the volumes of the solutions, we can calculate the concentrations of the remaining reactants:

concentration of Pb(NO3)2 = 0.00285 mol / 0.035 L = 0.0814 M
concentration of K2Cr2O7 = 0.0024 mol / 0.020 L = 0.12 M

Therefore, after the reaction, the concentration of lead nitrate is 0.0814 M and the concentration of chromic sulphate is 0 M (since it was completely consumed).