name _______________________
Introduction : Sure, it's easy to calculate the concentration of a solution. But can you actually make a solution with a given molarity? Is there anything unexpected that can happen when one compound is dissolved in another? The answer to these and other questions can be found in this lab.
Purpose : To calculate and then experimentally determine the molarity of two different solutions.
To understand the effect of dissolving a solute upon the volume of a solution.
Materials : 10 ml graduated cylinder rubber stopper (00) 50 ml graduated cylinder water denatured ethyl alcohol 2 droppers NaCl
(s)
Procedure 1
1. Calculate the molarity of the solution that results when 4.00 g of NaCl
(s)
is dissolved in 30.0 ml of water. (Show your work, use the correct # of sig. digits, etc., etc.) answer ___________
Measure exactly 30.0 ml of water using the 50 ml graduated cylinder. Mass exactly 4.00 g of NaCl
(s)
.
Carefully add the salt to the water in the cylinder - make sure none of the NaCl sticks to the sides - and stir until all is dissolved. Try not to lose any solution when you remove the stirring rod.
2. What is the final volume of your solution? ________
3. What is the molarity of your solution? answer ___________
4. Why does your experimental result differ from your original calculated value?
5. Write a hypothesis to explain why the dissolving of salt in water changes the volume of the solution.
6. Calculate the percent error between your calculated value and your experimental value (the accepted value).
7. Write a procedure for making 1.50 Liters of 1.62 M NaCl
(aq)
solution.

Procedure 2
8. Calculate the molarity of the solution that results when 5.0 ml of CH
3
OH
(l)
(methyl alcohol or methanol) is dissolved in 5.0 ml of water. (Show your work, use the correct # of sig. digits, etc., etc.) answer ___________
Measure exactly 5.0 ml of colored water using the 10 ml graduated cylinder. Using a plastic transfer pipet, carefully add methyl alcohol to the cylinder until the combined volume is exactly 10.0 ml. Add the alcohol slowly, holding the tip near the surface of the liquid in the cylinder so that the water and the alcohol do not mix.
9. Why does the methyl alcohol "float" on the water?
10. Can you tell at this point if the water and MeOH are miscible? Explain.
Tightly stopper the graduated cylinder and gently invert the solution a number of times until the solution is fully mixed. Remove the stopper but try not to lose any solution when you are removing it.
11. What is the final volume of your solution? ________
12. What is the molarity of your solution? answer ___________
13. Why does your experimental result differ from your original calculated value?
14. Write a hypothesis to explain why the dissolving of alcohol in water changes the volume of the solution.
15. Calculate the percent error between your calculated value and your experimental value (the accepted value).
16. Write a procedure for making 2.00 Liters of 6.74 M CH
3
OH
(aq)
solution.