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Chapter 8: Problem 1

Decide on the appropriate methods and equipment for the following procedures: (a) Preparing one litre of ethanol at approximately \(70 \% \mathrm{v} / \mathrm{v}\) in water for use as a general-purpose reagent. (b) Adding \(25.00 \mathrm{~mL}\) of concentrated hydrochloric acid to water (100 mL). (c) Adding \(10 \mu \mathrm{L}\) of propanone to a volumetric flask \((100.00 \mathrm{~mL}\) ) to produce an aqueous solution calibration standard for chromatography. (d) Titrating an unknown solution of sodium hydroxide (approximate concentration \(0.1 \mathrm{M}\) ) with sulphuric acid \((0.5 \mathrm{M})\).

Short Answer

Expert verified
The methods and equipment for these procedures range from utilization of a volumetric flask for mixing ethanol with water, a beaker and burette or graduated cylinder for achieving precise volumes of hydrochloric acid and water, micropipette or microsyringe for adding small volumetric quantities, and a burette, pipette or volumetric flask, and indicator in the case of a titration between sodium hydroxide and sulphuric acid.

Step by step solution

01

Procedure (a)

For preparing approximately 70% of ethanol in water as a reagent, a simple method is to use a volumetric flask. First, fill in approximately 700 mL of ethanol into a 1000 mL volumetric flask and then fill up the rest volume of the flask with water until the one litre mark.
02

Procedure (b)

For adding 25.00 mL of concentrated hydrochloric acid to water (100 mL), it is important to follow the general rule 'Add acid to water'. A suitable equipment for this would be a beaker and a burette or graduated cylinder. Measure 100 mL of water in the beaker. Measure out 25 mL of the hydrochloric acid using the burette or graduated cylinder and add it slowly to the water while stirring to ensure proper dilution.
03

Procedure (c)

For adding 10 μL of propanone to a volumetric flask (100.00 mL) to produce an aqueous solution calibration standard for chromatography, the appropriate equipment will be a micropipette or a microsyringe, owing to the very small volume of propanone required. Measure out the 10 μL propanone and add it to the volumetric flask, then add water up to the 100 mL mark.
04

Procedure (d)

Titrating an unknown solution of sodium hydroxide (approximate concentration 0.1 M) with sulphuric acid (0.5 M) would require a burette filled with sulphuric acid, a pipette or volumetric flask for consistent volumes of sodium hydroxide and a suitable indicator. Start by adding a measured volume of sodium hydroxide solution to a conical flask. Fill the burette with sulphuric acid. Add the sulphuric acid to the sodium hydroxide solution drop by drop while stirring until end point (a color change indicating that all sodium hydroxide has reacted).

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Most popular questions from this chapter

After reading this chapter, prepare a streetwise protocol explaining how to use a pipettor to deliver a specific volume, say \(500 \mu \mathrm{L}\) (e.g. using a Gilson Pipetman \(^{\oplus}\) or an alternative if your department does not use this type). Ask another student to evaluate your protocol and provide you with feedback - either by reading through your protocol or by trying it out with a pipettor as part of a class exercise (check with a member of staff before you attempt this in a laboratory).
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