Select the best answer by circling A B or C below and if app

Select the best answer by circling A, B or C below, and if applicable, fill in the number of grams. You work as a summer student in a lab to help a postdoctoral fellow in her research. One day she e t on your bench a small vial containing 6 g of vitamin Z powder and a note asking you to prepare 20 ml of a 1M solution while she attends a seminar (use water to make the solution, she wrote). You start this task by checking the molecular weight of Vitamin Z (300 g/mol). When the postdoc comes back from the seminar: You complain that there is not enough powder and you need _____ g more to prepare this solution. You give your solution to the postdoc and thank her for having calculated the exact amount of powder needed, (but you think that she could have told you that!) You return the leftover _____ g to the postdoc together with the solution. If you used 6g of vitamin Z powder to make 20 ml of solution, what is the % concentration of this solution? 6g per 20 ml equivalent to 30g per 100 ml (multiply 20ml by 5 to get to 100 ml) You work in a lab as a summer student. One of your tasks is to make sure that there is enough cell culture medium containing antibiotics to grow bacteria. One day you realize that there is only 5 ml of 10% Antibiotic stock solution in the freezer. You decide to use it all to prepare the working culture medium with 0.01% antibiotic. In the lab there is plenty of growth medium without antibiotics. You remember the equation to make dilutions of stock solutions. You usually use this formula to calculate the required volume of a stock solution, but you realize it can apply here as well, even though the unknown is the final volume. So, you make that dilution. Given that there each bacterial culture requires 200 ml of medium with 0.01% antibiotics, how many cultures can you grow? Explain your reasoning. You are performing an enzymatic reaction to digest DNA and nothing works for you. You need to find out why. You added the enzyme and the DNA to the reaction yourself and you are sure you did it right. It must be the digestion buffer. The working solution for the digestion buffer should contain 400 mM Tris, pH 8.0 and 125 mM MgCl_2. First, you ask your colleague how he made the digestion buffer and he says: \"I mixed 0.2 ml of 2M Tris, pH 8.0 stock solution 0.25 ml of 5M MgCl_2 stock solution and I completed the solution with 0.55 ml water to make a final volume of 1ml.\" Before checking your colleague\'s calculation, what Important question do you have to ask first for this specific solution? (not a generic question about all solutions) You are satisfied with his answer to a) and you believe he made a dilution error. You use the equation that applies to dilutions to check his calculations. Aha! you find the problem. What is it and how did you find out?

Solution

A. Final solution to be made = 20 ml of 1 M solution of vitamin.

Molarity = moles/ L of soln. 1 mole of Vitamin is 300g/mole

in 1000ml, 300 g of vitamin added.

in 1 ml , 0.3 g of vitamin added. In 20 ml 6 g vitamin needed.

Hence, the answer is 0 g.

Hence