Dilution Lab – Preparation of Sodium Hydroxide and Hydrochloric Acid Solutions
Purpose:
To prepare 250.0 mL of 0.100 M solution from a standard 3.0 M stock solution of HCl (aq)
To prepare 100.0 mL of an assigned concentration of sodium hydroxide when starting with a solid
Introduction:
The dissolving process when making acids and bases is generally exothermic. Due to this, it is important
that the dilution process occurs in a large volume of water to absorb the heat that is produced.
The stock acid will be diluted by adding the strong acid to water.
The basic solution will be produced as solid NaOH is added to water, then diluted to the new
concentration.
Materials &
Method
100.0 mL volumetric flask
250.0 mL volumetric flask
Solid sodium hydroxide
3.0 M hydrochloric acid
pipette
pipette bulb
100 mL beaker
250 mL beaker
10 mL graduated cylinder
Part A: Dilution of strong acid
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Calculate the volume of 3.0 M HCl (aq) required to make 250.0 mL of 0.100 M acid
Have this amount confirmed and checked by the instructor
(4 marks)
Take ~200 mL of distilled water and place it into your 250.0 mL volumetric flask
Carefully take approximately 10.0 mL of the 3.0 M HCl (aq) from the class beaker into your graduated cylinder
Pour the 10 mL of concentrated acid in to a 100 mL beaker
Pipette the correct amount, that has been checked by the instructor, into the 250.0 mL volumetric flask
Fill the 250.0 mL volumetric flask with a water bottle until the meniscus reaches the line
Carefully invert the 250.0 mL volumetric flask several times to ensure proper mixing
Place your acid in the class storage bottle for future use
Part B : Dilution of sodium hydroxide
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Calculate the amount of mass of sodium hydroxide required to make 100.0 mL of 0.750 M NaOH.
Have the number of moles of solute (4 marks) and mass of solute (4 marks) checked by the instructor.
Place ~ 70 mL of water into the 100.0 mL volumetric flask
Mass and then quickly add the required amount of solid sodium hydroxide into the 100.0 mL volumetric flask
Fill the 100.0 mL volumetric flask with a water bottle until the meniscus reaches the line
Carefully invert the 100.0 mL volumetric flask several times to ensure proper mixing
Place your acid in the class storage bottle for future use
Observations:
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2)
Was the process of diluting acid an exothermic process or an endothermic process? How do you know? (2 marks)
Was the process of preparing a basic sodium hydroxide solution exothermic process or an endothermic process?
How do you know? (2 marks)
Calculations :
Show your work from the calculations required above.
Questions to Answer:
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TOTAL
Write the total ionic and net ionic equations for the dilution of the acid. ( 2 marks)
Write the total ionic and net ionic equations for the preparation of the base. ( 2 marks)
Why are volumetric flasks used in this experiment? ( 1 mark)
Why is a pipette used in this experiment? ( 1 mark)
Why is it likely that the concentration of the sodium hydroxide solution will be imprecise? ( 2 marks)
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