Neutralizing the thermal determination of the device, each part of the action

Cardboard and crumbled foam are used to reduce heat loss.

If used hydrochloric acid with sodium hydroxide.

The amount and concentration of the solution are the same, then the reaction is not guaranteed to be sufficient, so it is generally necessary to let one reactant in excess to ensure that the other reactant is completely reactive.

Neutralize the heat. The assay steps are as follows:

1. Instrument: large beaker.

Small beaker, thermal insulation shredded paper, cover, thermometer.

Ring stirring rod, graduated cylinder.

2. Drug: 1mol LHCI NaOH.

3. Put shredded paper in a large beaker, put a small beaker, and shredded paper with thermal insulation materials around. Rent is defeated.

4. Measure 50 ml of HCI in a small beaker, measure the temperature, and record.

5. Measure 50 ml of NaOH, measure the temperature, and record.

6. In a small beaker, carefully inject sodium hydroxide.

The solution, the cover, the thermometer, and the tung ring stirring rod are stirred to read the maximum temperature.

7. Parallel experiments were carried out three times to calculate the mean.

Note: The disadvantages are purely averaged.

Heat of neutralization: 1. Heat of neutralization, in dilute solution, strong acid.

Neutralization reaction occurs with strong alkali.

The amount of heat released when 1 mol of liquid water is generated.

Assay steps: 1. In a large beaker.

Styrofoam underlay.

or paper scraps) so that the mouth of the small beaker is level with the mouth of the large beaker. Then fill the large and small beakers with broken styrofoam (or paper strips), use Duan Xiao styrofoam board (or cardboard) as a cover plate on the large beaker, and open two small holes in the middle of the plate to make the thermometer.

and the annular glass stirring rod through, as shown in the figure below.

2. Use a graduated cylinder.

Measure 50 ml mol l hydrochloric acid, pour it into a small beaker, and measure the temperature of hydrochloric acid with a thermometer, recorded in the table below. Then rinse the acid off the thermometer with water.

3. Use another graduated cylinder to measure 50 ml mol L NaOH solution, and measure the temperature of NaOH solution with a thermometer and record it in the following table.

4. Put the thermometer and annular glass stirring rod into the hydrochloric acid of the small beaker, and pour the NaOH solution in the graduated cylinder into the small beaker at one time (do not spill the liquid outside). Gently agitate the solution with a ring glass stir bar and read the mixed solution accurately.

The maximum temperature, denoted as the termination temperature, is noted.

5. Repeat the experiment twice to take the average value of the measured data.

as a basis for calculations.

Heat of neutralization, the heat released when a strong acid and a strong base are neutralized to produce 1mol of liquid water in a dilute solution.

Determination steps: 1. Put foam plastic (or paper scraps) at the bottom of the large beaker so that the mouth of the small beaker is level with the mouth of the large beaker. Then fill the large beaker with broken styrofoam (or paper strips), use a styrofoam board (or cardboard huishuo board) as a cover plate on the large beaker, and make two small holes in the middle of the plate to pass through the thermometer and the annular glass stirring rod.

2. Use a graduated cylinder to measure 50 ml mol l hydrochloric acid, pour it into a small beaker, and measure the temperature of hydrochloric acid with a thermometer, and record it in the following table. Then rinse the acid that the thermometer has failed to guess with water.

3. Use another graduated cylinder to measure 50 ml mol L NaOH solution, and measure the temperature of NaOH solution with a thermometer and record it in the following table.

4. Put the thermometer and annular glass stirring rod into the hydrochloric acid of the small beaker, and pour the NaOH solution in the graduated cylinder into the small beaker at one time (be careful not to spill it outside). Gently stir the solution with an annular glass stir bar and accurately read the maximum temperature of the mixed solution, which is noted as the end temperature, and write it down.

5. Repeat the experiment twice, and take the average value of the measured data as the basis for calculation.

1. It must be a dilute solution of acid and alkali, because the concentrated acid solution and the concentrated alkali solution will be exothermic when they are diluted with each other. Mega mill.

2. The reaction of dilute solution of strong acid and strong base can ensure that the neutralization heat of H+(AQ)+OH-(AQ)=H2O(L) is 57 3 kJ·mol 1, while the neutralization heat of weak acid or weak base is less than 57 3 kj·mol 1 due to ionization in the neutralization reaction.

3. Based on the generation of 1 mol of water.

4. The reaction cannot generate precipitates (such as Ba(OH)2+H2SO4=BASO4+2H2O).

The experiment of the determination of the neutralization heat is to determine the neutralization heat of the reaction of strong acids and bases, and the experimental process is to put foam plastic (or paper strips) at the bottom of the large beaker, so that the mouth of the small beaker is level with the mouth of the large beaker.

Then fill the large beaker with broken styrofoam (or paper strips) between the large and small beakers, use a styrofoam board (or cardboard) as a cover plate on the large beaker, and make two small holes in the middle of the plate to pass through the thermometer and the annular glass stirring rod. Take a maximum of 50 ml mol l of hydrochloric acid with a graduated cylinder, pour it into a small beaker, and measure the temperature of hydrochloric acid with a thermometer.

Then rinse the acid off the thermometer with water. Measure 50 ml mol L of NaOH solution with another graduated cylinder and measure the temperature of NaOH solution with a thermometer, noted in the table below. Place the thermometer and annular glass stir rod into the hydrochloric acid of a small beaker, and pour the NaOH solution from the graduated cylinder into the small beaker at once (be careful not to spill it outside).

Gently agitate the solution with an annular glass stir bar and accurately read the maximum temperature of the mixed solution, which is denoted as the termination temperature, as recorded in the table below. The experiment was repeated twice, and the average of the measured data was taken as the basis for calculation.

Results of neutralization thermal experiments

The heat of neutralization is the heat emitted by the neutralization reaction of the acid and base in a dilute solution to produce lmol of water, why should it be specified in a dilute solution? Because if in a concentrated solution, even if it is a strong acid or a strong base, it cannot be completely ionized as a self-hailizing ion by moving ions because there are not enough water molecules.

In the process of neutralization reaction, it will be accompanied by the ionization of acid or base and the hydration of ions, ionization to absorb heat, ion hydration to release heat, different concentrations of this heat is different, so the value of neutralization heat is different, so there is no unified standard.

The steps are as follows. <>

1 Instrument: large beaker, small beaker, thermal insulation shredded paper, cover, thermometer, annular stirring rod, graduated cylinder.

2. Drug: 1mol LHCI NaOH.

3. Put shredded paper in a large beaker, put a small beaker, and shredded paper with thermal insulation materials around.

4. Take 50 ml of HCI in a small beaker, measure the temperature, and record.

5. Take 50 ml of NaOH for orange circles, measure the temperature, and record.

In a small beaker, carefully inject the sodium hydroxide solution, cover plate, thermometer, ring stirring rod and read the highest temperature.

Parallel experiments three times to calculate the mean!

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Tools Raw materials.

Large beaker, round and small beaker, thermal insulation shredded paper, cover, thermometer, annular stirring rod, graduated cylinder.

1 Reaction Principle.

h+(aq)+oh-(aq)=h2o(l) δh= kj·mol-1

By measuring the temperature change of a certain amount of acid and alkali solution before and after the reaction, the heat released by the reaction is calculated, and the heat of neutralization is obtained.

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2. Experimental description.

1) In the determination of neutralization heat, the concentration of NaOH solution is slightly greater than that of hydrochloric acid to ensure that the HCl reaction is complete. If the concentration of acid and alkali is equal, the method of slightly excessive alkali volume can be used to achieve this purpose.

2) Formula for calculating the heat of neutralization.

h= kj/mol

3) If a weak acid (or weak base) is used instead of a strong acid (or strong base) in the experiment, the value of neutralization heat is small because the ionization of the weak acid (or weak base) out of H+ (or OH) needs to absorb heat; If the heat of neutralization is measured by the reaction of concentrated sulfuric acid with a strong alkali, the value of the measured heat of neutralization is large because the dilution of concentrated sulfuric acid needs to be exothermic.

4) In order to improve the accuracy of the determination of the heat of reaction, attention should be paid to "fast" (the experimental operation should be fast to minimize heat loss), "accurate" (accurately measure the temperature and volume of the liquid), and "thin" (the concentration should not be too large, to avoid the release of dilute heat, but also to avoid the concentration being too small).

5) To use the same thermometer, the mercury ball of the thermometer should be completely immersed in the solution and the maximum temperature during the change should be read.

6) The annular glass stirring rod cannot be replaced by iron wire, if it is replaced by iron wire, it will release heat due to the reaction between iron wire and acid, and the heat transfer of iron wire is fast, so that the test results are inaccurate.

7) For quantitative experiments, the experimental steps need to be repeated, and the average of the data of the three experiments should be taken, but the data that are too different should be discarded.