Compound C (MW = 550) is provided at a concentration of 25g/100mL. 1mL is taken and compound D is to be added (MW = 1025, concentration = 75mM) to give a final ratio of compound C:D of 4:1. What volume of compound D is to be added?

To solve this problem, we need to determine the volume of compound D that needs to be added to achieve the desired ratio with compound C.

First, let's calculate the number of moles of compound C in 1 mL of the solution. We know that the concentration of compound C is 25g/100mL, which is equivalent to 250g/L or 0.25g/mL. To convert grams to moles, we need to divide the mass by the molecular weight of compound C (550 g/mol):

Number of moles of compound C = mass / molecular weight
= 0.25g / 550 g/mol
= 0.0004545 mol

Next, we need to determine the number of moles of compound D that should be added to achieve the 4:1 ratio. The desired ratio is 4 parts of compound C to 1 part of compound D. In other words, for every 4 moles of compound C, we need to add 1 mole of compound D.

Since we know the number of moles of compound C in 1 mL (0.0004545 mol), we can now calculate the number of moles of compound D needed:

Number of moles of compound D = (Number of moles of compound C) / (4 parts of C: 1 part of D)
= 0.0004545 mol / (4/1)
= 0.0004545 mol / 4
= 0.0001136 mol

Finally, we need to calculate the volume of compound D that corresponds to the calculated number of moles. The concentration of compound D is given as 75mM, which means 75 millimoles per liter. To convert moles to millimoles, we multiply the number of moles by 1000:

Number of millimoles of compound D = Number of moles of compound D * 1000
= 0.0001136 mol * 1000
= 0.1136 millimoles

Now, let's calculate the volume of compound D needed using the concentration:

Volume of compound D = Number of millimoles / Concentration
= 0.1136 millimoles / 75 mM
= 0.001515 liters or 1.515 mL

Therefore, to achieve a final ratio of 4:1 (compound C:D), 1.515 mL of compound D needs to be added to 1 mL of compound C solution.