Select the best answer by circling A, B or c below, and if applicable, in the nu

Question

Select the best answer by circling A, B or c below, and if applicable, in the number grams. You work as a summer student to help a postdoctoral fellow in her research. One day she left on your bench small containing 6g of vitamin z powder and a note asking you to prepare 20 ml of a 1M solution while she attends seminar (use water to make the solution, she wrote). You start this task by checking the molecular weight of vitamin g/moll. 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 her the of solution to the p and thank for having calculated exact amount 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 percentage concentration of this solution? 6g per 20 ml equivalent to 30g per 100 ml (multiply 20ml by 5 to get to 100 m) You work in a lab as a summer student. One of your tasks is to make sure that there is

Explanation / Answer

Molarity = Moles/Volume in liters

Since the solution volume had to be 20mL ( = 0.02 L) with a molarity of 1M, this means that the requirement of moles of vitamin is: 0.02*1 = 0.02 moles

Since MW = 300g/mole, so mass of vitamin powder needed = 0.02*300 = 6g

Thus the amount of powder was given in exact amount.

20 mL of the solution contains 6g powder,so,

100mL will contain: 6*5 = 30 g powder

Thus, (w/v)% of the solution = 30%

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