Number Of Moles Of Hydrochloric Acid example essay topic

My aim in this investigation is to analyse a solution of hydrochloric acid and calculate the concentration of acid it contains in gdm. Apparatus Solution of Hydrochloric Acid (HCL - 0.3 molar) Solution of Calcium Hydroxide Ca (OH) 100 cm Conical Flask Pipette (25 cm) Pipette Filler Burette Distilled Water Volumetric Flask Funnel Methyl Orange Indicator White Tile. Method 1. Collect all the apparatus and set up as shown in diagram below. 2. Hydrochloric Acid should be diluted.

I have to dilute the acid from 0.3 molar to 0.03 molar, because at 0.3 mol / dm it is 20 times more concentrated than CA (OH). Use a pipette and pipette filler to transfer 25 cm of hydrochloric acid into a graduated flask. The rest of the flask should be filled with distilled water until the solution reaches the faint line on the neck of the graduated flask. This shows that 250 cm has been reached.

3. After rinsing, the burette is filled with acid to the "0" mark. This should be done using funnel to prevent any spillage's. The acid should run through the whole of the burette. This is to make sure that the acid is the only solution in the burette. 4.

A few drops of indicator, Methyl Orange are added to the flask (methyl orange is being used as the titration is between a strong acid and a weak alkali), which is placed on a white tile underneath the burette. 5. Record initial burette reading before beginning the titration (should be 0 cm always). 6. Acid is added to the flask from the burette. The flask is swirled continuously to mix the chemicals.

7. This process continues until the indicator just changes colour (red / magenta pink). This is the end-point. The white tile helps to identify any colour changes more clearly. 8. The volume of acid used from the burette is noted.

9. The process is repeated until at least 2 results are within 0.1 cm of each other. These are concordant results. 10. Results obtained should be recorded in a suitable results table. 11.

Apparatus should be cleaned away safely and all glassware should be washed with distilled water. Variables In this investigation, the only variable there will be is the amount of hydrochloric acid added to the conical flask. Risk Assessment During this experiment, corrosive solutions (such as Calcium Hydroxide and Hydrochloric Acid) will used so eye protection such as goggles should be worn at all times incase of any incidents of wild reactions which would result to any splashes into the experimenter's eyes. Calcium Hydroxide is very corrosive which cause the skin to burn and irritate if spilt on it. Calcium Hydroxide should be kept away from water because it reacts very vigorously with it. If any of the Calcium Hydroxide enters the eye then it must be washed with water as soon as possible.

If Calcium Hydroxide comes into contact with skin then the area affected should be washed with water and should seek medical care. Calcium should be disposed of by diluting it with large quantities of water and pouring it down a drain. ANALYSIS Table Of Results 1st Titre (cm) 2nd Titre (cm) 3rd Titre (cm) Start (Initial) Finish (Final) 22.30 22.40 22.40 Overall Titre 22.30 22.40 22.40 The overall titre is worked out using the following method: Initial Reading - Final Reading = Overall Titre (cm) The average titre is worked out using the following method: 1st titre + 2nd titre + 3rd titre = average titre (cm) 3 Average titres of concordant results = 22.30 + 22.40 + 22.40 3 = 22.366667 = 22.37 cm (rounded to nearest decimal place) Using the average titre I am going to calculate the number of moles of Hydrochloric Acid (HCL). Firstly divide the average titre by 1000 so that my result is covered into dm to get the volume.

The average titre = 22.4 1000 = 0.0224 dm This is the volume Now I am going to use the concentration of Hydrochloric Acid used (after dilution which is 0.03 moles dm) to calculate the number of moles of Hydrochloric acid by using the formula. Number of moles = Concentration (mol / dm ) x Volume (dm) = 0.03 x 0.0224 = 0.000672 moles I am going to use the number of moles of Hydrochloric Acid used to calculate the number of moles of Calcium Hydroxide. I did not use the value given as it was just an estimate (0.015). As you can see from the equation the ratio of Calcium Hydroxide to Hydrochloric Acid is 1: 2, therefore half of the number of moles of Hydrochloric Acid was used.

Number of moles of Hydrochloric Acid = 0.000672 2 = 0.000336 Number of moles of Calcium Hydroxide = 0.000336 moles Now using the number of moles of Calcium Hydroxide and the volume of Calcium Hydroxide I am going to calculate the concentration using the formula: Concentration (mol dm) = Number of moles (m) Volume (dm) Volume = 25 cm 1000 = 0.025 dm Concentration = 0.000336 0.025 = 0.01344 mol / dm I am now going to convert the moldm to gdm by multiplying by the molar mass Molar mass of Calcium Hydroxide = 40 + (16 x 1) x 2 = 74 g Concentration in gdm = 0.01344 x 74 = 0.9946 gdm The presumed concentration for the Calcium Hydroxide was 0.015 moldm but from my calculations it worked out to be 0.99456 mol gdm. This was just over half the concentration that I had predicted it would be. EVALUATION From looking at my results I can perfectly see that there were no anomalous results because the overall titres were very close to one another. This is because the technique I used tried to make everything as accurate as possible. I feel that the main errors occurred whilst I was using the pipette filler because it was very hard to handle. Sometimes there would be some air left in it.

I could have also had made some errors when it came to recognising the correct endpoints on the measuring equipment (volumetric flask, pipette filler etc... ) Here are some percentage errors that could have affected my results: Burette 0.05 + 0.05 x 100 = 0.45% 22.3 0.05 + 0.05 x 100 = 0.45% 22.4 0.05 + 0.05 x 100 = 0.45% 22.4 Total % error for the burette = 0.45 + 0.45 + 0.45 = 1.35 = 4.5 3 Pipette A 25 cm pipette was used to measure the solutions this introduces an error of 24% On the 25 cm pipette it states that there is a error of 0.06. 0.06 = 0.0024 25 0.0024 x 100 = 0.24 Volumetric Flask A 25 cm volumetric flask which was used to measure the diluted acid introduces an error of 0.15%. Indicators could also of affected the results of my experiment because excess indicators will require a different volume of solution to be added from the burette before the required colour change is obtained. My results are reliable to a great extent because the titration was carried out three times to record concordant titres.

All of the glassware was also washed thoroughly between use to prevent any contamination and blockages of dried up Hydrochloric Acid. The percentage errors will affect the overall results because sometimes not enough or too much of the acid or alkali was added. I cannot find out if too much or too little was added. The procedure that I used was time consuming but it kept any errors to a minimum but this factor did not prevent the percentage errors from occurring and affecting the results. web.