Calculate Molarity of Co^2+ in a solution

[larry21]

Homework Statement

Calculate the molarity of the Co^2+ ion in each of the solutions 1-5. The new molarity is given by the molarity of the stock solution multiplied by the dilution factor.

Solution: Co(NO3)2

Original molarity: 0.160

Dilution #1: none
D#2: 12mL to 16mL
D#3: 8mL to 16mL
D#4: 4mL to 16mL
D#5: 2mL to 16mL

Please help I do not understand what I'm supposed to do. Thank you.

 

[kk727]

Co(NO3)2 --> (Co)+2 + 2(NO3)-1

Look at the coefficients. Your molarity of Co(NO3)2 will be the same as the Co+2 ions.

Dilution Factor = Starting Volume/Ending Volume

For #1, if you are not diluting the solution, you are not adding water. Your molarity will not change.

For #2, you are starting with 12 mL of 0.160M Co(NO3)2. Diluting to 16 mL will lower your molarity. Your dilution factor would be 12/16, or 0.75. Multiply this by the old molarity to get your new molarity.

Correct me if I'm wrong!

 

[larry21]

Yes, that is what I thought as well, I just don't know what it meant by "Calculate the molarity of the Co^2+ ion in each of the solutions 1-5"

So the above statement just means to calculate the molarity of the Co(NO3)2 solution in each of the 5 diluted solutions?

 

[Borek]

Does it help: you have a 1M (mole/L) solution of CaCl₂. CaCl₂ is completely dissociated. That means solution contains 1M of Ca²⁺ and 2M of Cl^-.

Please note when asking homework type questions you should follow the template, otherwise you risk your question will be deleted. That's in forum rules.

 

[donutz610]

Try M1V1=M2V2 were m is your molarity and v is your volume. With the dilution factor you should be able to calculate your original and final volumes then plug them into get your other molarity.