Experiment 5 Chemistry Form 6 1j5a4v

Name: Experiment 5 Topic

: Volumetric – stoichiometry

Purpose

: to determine the exact concentration of monobasic acid, HX

Question

: you are provided with a monobasic acid, HX, with a concentration in the range of to

. You are required to plan and carry out an experiment to

determine the exact concentration of the HX solution provided. Materials 

KA 1 is a solution containing an unknown acid, HX with a concentration varying from



KA2 is a solution containing sodium hydroxide, NAOH with a concentration of 1.0 mol dm-3



Phenolphthalein as indicator

Apparatus Weighing bottle, volumetric flask 500 ml or 500 cm3, electric balance, filter funnel, wash bottles, droppers, beaker, retort stand, burette, pipette, sucker, conical flasks, white tiles, distilled water and a spatula. Precaution 1. Sodium in metal form is highly reactive. Wearing protective gears and precautionary steps are taken to minimize accidents during the process of cutting Sodium (natrium , Na) solids. 2. Handle sodium metal with gloves. Sodium is reactive when come in with water. Introduction Preparation of a standard solution of sodium hydroxide, NaOH is done by dissolving pure sodium metals in water, react with

In the process, small sparks are seen as the reaction takes place. The

ions

ions to form sodium hydroxide solution which used in second part of the experiment.

Sodium hydroxide solution can be prepared by dissolving sodium hydroxide pellets with certain amount of water to get suitable molarity. Procedure: Part 1: preparing a standard solution of 1.0 mol dm-3 sodium hydroxide, NaOH. 1. A electronic balance and weighing bottle are used to weigh 10 g of sodium hydroxide powder using a spatula. 2. The solid are carefully tipped into a beaker containing distilled water. 3. Any solids remaining in the weighing bottle is washed into the beaker into the beaker with a wash bottle.

4. After dissolving the solid, the final solution is carefully transferred into the volumetric flask using a glass rod and a filter funnel. 5. About reaching the volume needed, stop at 1 or 2 cm from the line. By using a dropper or a wash bottle, carefully filling it until the mark. 6. The flask is then shaken to mix the solution thoroughly. 7. The solution prepared is a standard solution of 1.0 mol dm -3 or 1.0M.

Part 2: Titration of 1.0 mol dm-3 sodium hydroxide, NaOH, with an unknown acid, HX with a concentration between 0.5 mol dm-3 to 1.0 mol dm-3 Pipette 25cm3 of KA1 into the titration flask. Titre solution with KA2. Repeat titration as many times as you think it is necessarily to achieve accurate results. Results: Part1 : calculation Molar mass of NaOH = 23+16+1 =40g

Use:

Part 2 Titration

Rough

Accurate First

Second

Final reading / cm3 Intitial reading/ cm3 Volume of KA2/ cm3 i)

25cm3 of KA 1 required __________cm3 of KA 2 for a complete reaction.

MODIFIED LAST ON 21/7/2012 LOO FU HONG

Third