The preparation and measurement of hcl-based analytical experiment in university

Answer 1

1. ** The preparation of the HQ solution **
- The volume of concentrated sulfuric acid needed to prepare a solution of a certain concentration (such as 0.1moldm3) was calculated. For example, to prepare a 1000cm 3 0.1moldm- 3 solution of the solution, it was necessary to first calculate according to the law of dilute, where c1V1 = c2V2, where c1 and V1 are the concentration and volume of the concentrated solution of the solution, and c2 and V2 are the concentration and volume of the solution to be prepared. Assuming that the concentration of concentrated sulfuric acid is 6 mol-dm- 3, we can get the result of the experiment. After measuring the volume of concentrated sulfuric acid, dilute it with distilled water to form a solution of 1000cm-3, store it in a reagent bottle and label it for later use. You can also use a small measuring cylinder to take 8.2 ml of concentrated sulfuric acid, add water to dilute it to 1000ml, and mix it well to obtain a 0.1 mol. L - 1 sulfuric acid solution.
2. ** Standard solution for the measurement of the standard solution of the hydrogen clo **
- ** Choice of reference materials **: The reference materials used to mark the standard solution of HQ are Na2CO3 and Na2B4O7·10H2O.
- ** Using Anhydrous Natrium Carbonic as an example, the steps for the measurement **
- Take about 0.2g of reference absolute carbon dioxide dried at 270 - 300 ° C to a constant weight, accurately weigh 3 portions, and place them in 250ml conical flasks.
- After dissolving it in 50ml of distilled water, add 10 drops of mixed indicator of methylethyl-bromocresoll green.
- Titrate the solution with a 0.1 mol-L- 1 solution of sulfuric acid until the solution turns from green to dark red. When it is close to the end point, boil it for 2 - 3 minutes to remove the carbon dioxide in the solution, and then continue to titrify to the end point. According to the relationship between the two stoichiometries, the mass of the weighed absolute Na2CO3, the volume of the consumed solution, and the mole mass of the absolute Na2CO3, the accurate concentration of the solution was calculated according to the formula, c(HQ)= 2frac {2m (Na2CO3)}{V(HQ)M(Na2CO3)}.
- ** Using Borax as an example, the steps for the measurement (if Borax is selected as the reference material)**
- Accurately weigh a certain amount of tribution, place it in a conical flask, and add an appropriate amount of water to dissolve it.
- According to the reaction [Na2B4O7 + 2HC1 + 5H2O = 2NaCl4 + 4H3BO3], the chemical measurement point [pH5.1], select a suitable indicator (such as methylared).
- Titrate the solution to the end point with the solution to be labeled. According to the mass of the weighed meteorite [m(Na2B4O7·10H2O)], the volume of the consumed solution [V(HQ)], and the mole mass of meteorite [M(Na2B4O7·10H2O)], calculate the accurate concentration of the solution according to the formula [c(HQ)]=[frac{2m (Na2B4O7·10H2O)}{V(HQ)M(Na2B4O7·10H2O)}.

During the entire experiment, he also needed to be familiar with the use of the apparatus such as the flask, pipet, and buret, including washing, rinsing, filling, blowing bubbles, reading, and so on. At the same time, he needed to accurately determine the end point of the Titration.
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