chemistry molarity?

Question

i want to prepare 100mL of a 0.125M solution of zinc iodide from the stock solution. how would i do this? assume you have a 100mL flask availabe. this is called a dillution. it is crucial that you be able to do this type of calculation.
how many moles of solute are you going to want to end up with the 100mL solution?
. how many milliliters of solution are you going to need to take from the stock solution to get the moles in a?

Answer 1

I can't give a specific answer untill I am told the molarity of the stock solution. However, since you need 100 ml of 0.125M ZnI2 solution you can see that you will need 1/10 of 1/8 of a mole of ZnI2 in you solution. So you just need to determine what volume of "stock solution" is required to contain this amount of ZnI2, add it to your 100ml flask, then dillute to 100ml with water. I have probably given you enough of an idea that you can solve it for yourself now.

Answer 2

First off Zinc Iodide is Zn(II)I2.

Take 100ml times 0.125 moles / 1000ml of ZNI2 solution = # moles solute. 0.0125 moles.

# ml sol. needed = 1000 because molarity is moles per liter or 1000 ml.