True or false? To prepare 20.0 mL of a 2.00 M solution of hydrochloric acid from a 10.0 M stock solution, you should take 4.00 mL of the stock solution and add 20.0 mL of water. If true, verify this with calculations. If false, explain why including calculations and state how to correctly make the desired solution.
I'm not necessarily looking for someone to solve the problem for me (feel free to, though). I'm just having a hard time figuring out how to do it. Thanks!
I'm not necessarily looking for someone to solve the problem for me (feel free to, though). I'm just having a hard time figuring out how to do it. Thanks!
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As you say - I am not going to do the calculations:
But: You are correct that you must use 4mL of the 10.0M solution. This must be diluted to a final volume of 20mL. Then the molarity will be 2.00M. If however, you take the 4.0mL of stock solution and add 20mL of water, your final volume will be 24.0mL. The final solution will have molarity of 1.67M
Note: I do not like to word the answers to these questions as: take 4.0mL of the stock solution and add 16.0mL of water .... etc. This is supposedly to get the final 20.0mL volume. In my experience the correct way to to do this in practice is to measure out 4.0mL of the stock solution and dilute with water to a final volume of 20.0mL. No reference is made to the volume of diluting water.
But: You are correct that you must use 4mL of the 10.0M solution. This must be diluted to a final volume of 20mL. Then the molarity will be 2.00M. If however, you take the 4.0mL of stock solution and add 20mL of water, your final volume will be 24.0mL. The final solution will have molarity of 1.67M
Note: I do not like to word the answers to these questions as: take 4.0mL of the stock solution and add 16.0mL of water .... etc. This is supposedly to get the final 20.0mL volume. In my experience the correct way to to do this in practice is to measure out 4.0mL of the stock solution and dilute with water to a final volume of 20.0mL. No reference is made to the volume of diluting water.