6.03 Calorimetry Lab
Results :
Calculation :
Part A
Molecular weight of 1M of NaOH = 23g/mol + 16g/mol + 1g/mol = 40g/mol
1M = 40g/mol dissolved in 1L and 20g dissolved in 500ml
20g of NaOH was used to prepare 500ml of 1M NaOH.
Part B
Molecular weight of 1M of HCl = 35.5g/mol + 1g/mol = 36.5g/mol
Specific gravity = 1.19kg/L
37% HC1 × 1.19kg/L = 0.44kg/L
Convert w/v to mol/v = = 12mol/L =
(12mol/L) = (1M)250ml = 20.83ml ≈ 21ml
21ml of concentrated HC1 is used to prepare 250ml of 1M of HC1.
Part C
For 0.1N of NaOH :
For 0.1N of HC1 :
(1M) = 50ml of NaOH
(1M) = 25ml of HC1
Part D
First trial
Second trial
Third trial
Initial volume, ml
0
11.3
21.8
Final volume, ml
11.3
21.8
33.4
Total volume of HC1 used, ml
11.3
10.5
11.6
Normality of HC1
= 0.0885 …show more content…
This buffering ability is achieved via the equilibrium between the acid and its conjugated base in the reaction.
According to Le Chartelier’s principle, if a strong acid is added to a buffered solution, or in other words containing a weak acid and its conjugated base, pH is not significantly changed. As a result, the hydrogen ions concentration increases less than what would be expected due to the amount of acid added. Following a similar process, adding a strong base consumes much less hydrogen ions than anticipated. Adding a strong acid or base would seriously change the pH of the solution in the absence of the buffer.
In the experiment, standardization of NaOH with HC1 solution is carried out. Solid NaOH is hygroscopic where significant amounts of water vapor can be absorbed. Also, as NaOH is a strong base, significant amounts of atmospheric carbon dioxide can be absorbed too. It is also clear that NaOH cannot serve as a primary standard and thus it needs standardization by a primary or secondary standard. NaOH solutions can be directly titrated versus standardized HCl using phenolphthalein or methyl red indicator. In this case, methyl red is used as an indicator. The colours change from red to completely purple pink indicate the standardization is achieved. If reasonable concentrations of the acid and base are used, very sharp end points can be achieved. The …show more content…
Besides, the conical flask should be stirred all along the titration to ensure the two solutions can be mixed evenly. Furthermore, repeat the experiment for getting the average readings to ensure the accuracy of the experiment. Lastly, keep the eyes in level with the liquid surface while reading the burette to prevent parallax
Calculation :
Part A
Molecular weight of 1M of NaOH = 23g/mol + 16g/mol + 1g/mol = 40g/mol
1M = 40g/mol dissolved in 1L and 20g dissolved in 500ml
20g of NaOH was used to prepare 500ml of 1M NaOH.
Part B
Molecular weight of 1M of HCl = 35.5g/mol + 1g/mol = 36.5g/mol
Specific gravity = 1.19kg/L
37% HC1 × 1.19kg/L = 0.44kg/L
Convert w/v to mol/v = = 12mol/L =
(12mol/L) = (1M)250ml = 20.83ml ≈ 21ml
21ml of concentrated HC1 is used to prepare 250ml of 1M of HC1.
Part C
For 0.1N of NaOH :
For 0.1N of HC1 :
(1M) = 50ml of NaOH
(1M) = 25ml of HC1
Part D
First trial
Second trial
Third trial
Initial volume, ml
0
11.3
21.8
Final volume, ml
11.3
21.8
33.4
Total volume of HC1 used, ml
11.3
10.5
11.6
Normality of HC1
= 0.0885 …show more content…
This buffering ability is achieved via the equilibrium between the acid and its conjugated base in the reaction.
According to Le Chartelier’s principle, if a strong acid is added to a buffered solution, or in other words containing a weak acid and its conjugated base, pH is not significantly changed. As a result, the hydrogen ions concentration increases less than what would be expected due to the amount of acid added. Following a similar process, adding a strong base consumes much less hydrogen ions than anticipated. Adding a strong acid or base would seriously change the pH of the solution in the absence of the buffer.
In the experiment, standardization of NaOH with HC1 solution is carried out. Solid NaOH is hygroscopic where significant amounts of water vapor can be absorbed. Also, as NaOH is a strong base, significant amounts of atmospheric carbon dioxide can be absorbed too. It is also clear that NaOH cannot serve as a primary standard and thus it needs standardization by a primary or secondary standard. NaOH solutions can be directly titrated versus standardized HCl using phenolphthalein or methyl red indicator. In this case, methyl red is used as an indicator. The colours change from red to completely purple pink indicate the standardization is achieved. If reasonable concentrations of the acid and base are used, very sharp end points can be achieved. The …show more content…
Besides, the conical flask should be stirred all along the titration to ensure the two solutions can be mixed evenly. Furthermore, repeat the experiment for getting the average readings to ensure the accuracy of the experiment. Lastly, keep the eyes in level with the liquid surface while reading the burette to prevent parallax