Question

A chemist prepares a solution of potassium dichromate K2Cr2O7 by measuring out 52.μmol of potassium dichromate into a 450.mL volumetric flask and filling the flask to the mark with water.

Calculate the concentration in /μmolL of the chemist's potassium dichromate solution. Round your answer to 2 significant digits.

Answer 1

Step-by-step explanation:

The first step in solving this problem is to use the given information to calculate the number of moles of K2Cr2O7 in the solution. We can do this using the formula:

moles = (mass in grams) / (molar mass)

The molar mass of K2Cr2O7 can be calculated as:

2(39.1 g/mol potassium) + 2(52.0 g/mol chromium) + 7(16.0 g/mol oxygen)

= 294.2 g/mol

Therefore, the number of moles of K2Cr2O7 in the solution is:

moles = (52.μmol) / (10^6 μmol/mol)

= 0.000052 mol

Next, we can use the definition of concentration to calculate the concentration of the solution:

concentration = (moles of solute) / (volume of solution)

In this case, the volume of the solution is 450 mL, which we need to convert to liters:

volume = 450 mL = 0.450 L

Substituting the values we have calculated, we get:

concentration = (0.000052 mol) / (0.450 L)

= 0.000116 mol/L

Finally, we need to convert this concentration to micromoles per liter, which we can do by multiplying by 10^6:

concentration = (0.000116 mol/L) x (10^6 μmol/mol)

= 116 μmol/L

Therefore, the concentration of the chemist's K2Cr2O7 solution is 116 μmol/L (rounded to 2 significant digits).