Chemistry Coursework
Investigation: To investigate how much energy is transferred as heat when an acid reacts with an alkali. The acid that I will be using is sulphuric acid and the alkali that I will be using is Sodium Hydroxide.
Introduction: Chemical reactions often involve changes in energy. When an acid reacts with an alkali, the energy change is called heat of neutralisation. Heat of neutralisation is the heat released when one mole of water is formed from neutralisation between one mole of hydrogen ions, H+, from an acid and one mole of hydroxide ions, OH- , from an alkali. For example, Sodium Hydroxide and hydrochloric acid react to produce a salt (sodium chloride) and water.
Na+(aq) + OH – (aq) + H+(aq) + Cl-(aq) Na+(aq) + Cl-(aq) + H2O (l)
During a neutralisation reaction the hydrogen ions from an acid react with hydroxide ions from the alkali to make water:
H+(aq) + OH- (aq) H2O (l)
The remaining ions in the solution make a salt.
You can calculate the energy change of the reaction using the formula:
Energy change (J) = m x s x t
The Term Paper on Potential Energy Kinetic Change Water
Thermochemistry Answer Key Assignments 1- 8 Page 1. Answers to Energy Assignment 1 1. Indicate whether the following scenarios illustrate matter possessing mainly potential energy, or kinetic energy. a) There are 30 liters of fuel in the tank of a stationary automobile. o Potential energy (chemical energy in fact) b) A large rock is perched at the edge of a 40 m cliff. o Potential energy (of the ...
Where m = the volume of liquid in the reaction mixture in cm3
(Assuming 1 cm3 of the reaction mixture has a mass of 1g)
s = the specific heat capacity of water (4.2 j/g °C)
t = the change in temperature in °C
Endothermic reactions take in energy from its surroundings. The energy is usually transferred as heat energy, from the system (reaction mixture) to its surroundings (environment).
In an endothermic reaction the temperature of the surroundings (environment) decreases and the temperature of the system (reaction mixture) increases. The temperature change can be measured using a thermometer. Some examples of endothermic reactions are:
* Electrolysis
* The reaction between ethanoic and sodium carbonate
CaCo3 + 2CH3COOH H2O + CO2 + (CH3COO) 2Ca
* The thermal decomposition of calcium carbonate in a blast furnace
In an endothermic reaction, the products must have more energy than the reactants therefore the overall empathy is positive, as shown in figure 1:
Figure 1: Graph showing an endothermic reaction
Exothermic reactions are the opposite of endothermic. An exothermic reaction transfers energy from the system to its surroundings. The energy is usually transferred as heat energy causing the reaction mixture to get colder and its surroundings to become hotter. The temperature increase can be measured using a thermometer. Some examples of an exothermic reaction are:
* Burning
* Neutralisation between acid and alkali
* The reaction between water and calcium oxide
Figure 2 shows a diagram of an exothermic reaction. In an exothermic reaction, the products must have less energy than the reactants therefore the overall empathy is negative.
Figure 2: Graph showing an exothermic reaction
Hypothesis + prediction:
The factor that I will be investigating is the temperature change when an acid reacts with an alkali. I am going to mix different volumes of acid (Sulphuric acid) and alkali (sodium hydroxide) solution and measure the change in temperature, which takes place.
The Essay on Observing Reactions of Sulfuric Acid
Assessment task 3 oral presentation summary Description of the experiment * Aim:To observe the reactions of sulfuric acid as an oxidising agent and as a dehydrating agent. Equipment: * 20mL of concentrated sulfuric acid * 20mL of 2mol/L sulfuric acid * 2 small pieces of each of copper, zinc and iron * Sandpaper * 10 test tubes * Test tube rack * 2g of sugar crystals (sucrose) * 2 wooden ice-cream ...
Sulphuric acid + sodium hydroxide odium sulfate + water
H2SO4 + NaOH NaSO4 +H2O
As the volume of sulphuric acid increases by 1cm3 and the volume of Sodium Hydroxide decreases by 1cm3, the temperature will increase, until the solution reaches neutralisation and then decrease after neutralisation has occurred. I predict that my experiment will show an exothermic reaction; this is because heat is given off from the system (reaction mixture) to its surroundings (environment) causing the temperature to increase, as shown in figure 2. There is more energy in the reactants than the products causing a decrease in the energy. Figure 2 also shows that heat is given off to its surroundings.
To test for this prediction I will add 12 cm3 of Sulphuric Acid and 18cm3 of Sodium Hydroxide in to a polystyrene cup with a thermometer placed inside the polystyrene cup, which will be covered with a lid. I will note the initial temperature, once the temperature has stopped rising, I will take a final temperature. I will repeat these steps several times by increasing sulphuric acid by 1cm3 and decreasing sodium hydroxide by 1cm3 each time for the rest of the volumes and record my results in a table (as seen in table 1).
Table 1: temperature change for each of the volumes of sodium hydroxide and sulphuric acid.
H2SO4 (cm3) | NaOH (cm3) | Temperature (°C) | Temperature change (°C) * |
| Exp 1 | Exp 2 | Exp 3 | Exp 1 | Exp 2 | Exp 3 |
12 | 18 | | | | | | |
13 | 17 | | | | | | |
14 | 16 | | | | | | |
15 | 15 | | | | | | |
16 | 14 | | | | | | |
17 | 13 | | | | | | |
18 | 12 | | | | | | |
*Temperature change calculated initial temperature – final temperate)
Other factors:
Other factors that may affect my experiment are: the cup and lid size and material, the acid, the alkali and temperature. The size of the cup and lid will affect the experiment because the larger the cup, the larger the surface area will be therefore there will be more heat loss. The material of the cup and lid as an affect on the experiment because different cups are made out of different materials therefore I will be using a cup and lid that is made out of polystyrene this is because polystyrene is a good insulator preventing minimal heat loss. The type of acid and alkali used can have an affect on the experiment as different acid and alkali react differently therefore this factor will be kept constant. A final volume of 30 will be maintained for example: 12 + 18 = 30, 13+17 = 30. This will be kept constant as reaction rates differ. The initial temperature will be 20.
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The chemical compound potassium nitrate is a naturally occurring mineral source of nitrogen. It is a nitrate with chemical formula KNO3. Its common names include saltpetre (from Medieval Latin sal petrae: “stone salt” or possibly “Salt of Petra”), American English salt peter, Nitrate of potash and nitre. The name salt peter is also applied to sodium nitrate. Description: ...
Preliminary experiment:
Aim: The aim of my preliminary experiment was to identify any problems that will occur and change them in order to make the results of my final experiment as accurate as possible. This will also reduce the occurrence of any anomalous results. The alkali that I used was Sodium Hydroxide and the acid that I used was Sulphuric Acid.
H2SO4 + 2NaOH 2H2O + NaSO4
This equation shows the neutralisation between sulphuric acid and sodium hydroxide producing a salt (sodium sulfate) and water.
I placed 25 cm3 of Sodium Hydroxide and 0 cm3 of Sulphuric Acid, then noted down the start temperature. I stirred the mixture and kept an eye on the thermometer, I took down the end temperature when the temperature stopped rising and calculated the temperature change. I then rinsed out the cup and repeated these steps but increasing sulphuric acid by 1cm3 and decreasing sodium hydroxide by 1cm3 for the rest of the volumes. I recorded my results in a table, as shown in table 2.
Results:
Table 2: NaOH + H2SO4 reacting to produce a temperature change
NaOH (cm3) | H2SO4 (cm3) | Initial temperature (°C) | Final temperature (°C) | Temperature change (°C)* |
25 | 0 | 26 | 26 | 0 |
24 | 5 | 26 | 28 | -2 |
23 | 10 | 28 | 35 | -7 |
22 | 15 | 35 | 35 | 0 |
21 | 20 | 35 | 30 | 5 |
20 | 25 | 30 | 29 | 1 |
* Temperature change calculated initial temperature – final temperature.
From table 2 in the preliminary results I can see that the temperature change increased until it reached 22cm3 of sodium hydroxide and 15cm3 of sulphuric acid where there was no temperature change. This is when neutralisation occurred. After this point the temperature change decreased showing an exothermic reaction. To improve my experiment I will be changing the range, as the interval range I used was too large. If I make the intervals smaller my results will be more accurate and precise and I will get a better and more precise idea of what volumes of sodium hydroxide and sulphuric acid have to be to achieve neutralisation.
The Essay on The Dissolving of Solid Sodium Hydroxide in Water Procedure
... record the initial temperature of each solution and record on your data table. 3. Add the sodium hydroxide solution to the acid solution in ... this would this affect the temperature change observed in the experiment? How would this affect the calculated enthalpy change? Heat would escape through the ...
Variables:
From my preliminary work the following variables are taken into consideration.
Independent – I will be changing the volume of the acid and alkali. I will be changing this so that I can clearly identify what volume the acid and the alkali have to be for neutralisation to occur.
Dependent – the variables that I will keep the same are: the size and material of the cup with the lid. I will be keeping the size the same because if I change the size there will be more heat loss as there will be a larger surface area. I will be keeping the material of the cup and lid the same because polystyrene is a good insulator therefore preventing any heat loss. These factors need to be controlled otherwise my results will not be accurate.
Risk Assessment:
Material | Risk | Precaution |
Sodium hydroxide | Corrosive | Wear gloves and goggles (eye protection) |
Hair blocking vision | Interfere with experiment | Tie hair back so that it will not interfere with my experiment. |
Breakage of thermometer | Can release a poisonous liquid called mercury. | I will use a thermometer that has alcohol instead of mercury, as it is less harmful. |
Spillage of sodium hydroxide | Burn the skin | I will make sure that the sodium hydroxide is not on the edge of the table. Incase it does fall I will have a large tub of water for major spillages. |
Sulphuric acid | Hazardous | Wear gloves, protective goggles as it can cause serious damage when in contact with skin. |
Filling burette | Burette can break | To minimize this risk I will make sure the burette is not on the edge of the table and I will make sure that It is at eye level. |
Transferring to cup | Solution can spill | To minimize this risk I will make sure the cup is steady therefore preventing the risk of the solution to spill causing damage. |
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Introduction In the experiment the magnesium reacts with the hydrochloric acid to create magnesium chloride and hydrogen. The balanced formula for this is: Mg(s) + 2HCL(aq) MgCl2(aq) + H2(g) Magnesium + hydrochloric acid Magnesium Chloride + Hydrogen Magnesium will react with hydrochloric acid, because it is higher in the reactivity series than hydrogen. The magnesium displaces the hydrogen in the ...
Final Experiment:
Following on from my preliminary experiment and variables considered. The final experiment was conducted.
Apparatus:
* Polystyrene Cup – I used this because polystyrene is a good insulator. To measure the heat of neutralization, the heat absorbed or released by the reaction is measured by a change in temperature. If heat is released into the room through the container, the measurement won’t be accurate.
* Polystyrene Lid – I used this because it is a good insulator and it will stop any heat produced from escaping.
* Thermometer – I used this to measure the temperature
* Sulphuric Acid – used to react with sodium hydroxide to neutralise.
* Sodium Hydroxide – used to react with sulphuric acid to neutralise.
* 2 burettes – I used this to measure the concentration of the acid and alkali. A burette is accurate to 0.05 cm3.
* Clamp stands – to securely hold the burettes in place.
Method:
* First gather all the equipment required for the experiment, as per apparatus list.
* Then put the burettes on the clamps and pour in the acid and alkali into each burette – make sure that the 0 on the burette is on eye level.
* In a polystyrene cup with a lid pour 12cm3 of sulphuric acid and 18cm3 of sodium hydroxide, note down the start temperature, stir the mixture and keep an eye on the thermometer.
* Once the temperature has stopped rising take down the end temperature and rinse the cup – if the solution is diluted pour it down the sink if not pour it into a bowl.
* Dry the cup to make sure there is no water left in the cup that can interfere with your results.
* Repeat the steps above for the rest of the volumes by increasing the sulphuric acid by 1cm3 and decreasing the sodium hydroxide by 1cm3 to make a final volume of 30cm3 for example: 12 + 18 = 30, 13 + 17 = 30
* Record the results in a table as follows:
H2so4 (cm3) | NaOH(cm3) | Temperature (°C) | Temperature change (°C) | Average temperature change (°C) |
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Climatic Change on the Earths Temperature The issue on global warming or the increase in the temperature of the Earths surface including both the air and the waters has been an issue for the humankind as far back as the late fourteenth century. In fact, people started to notice the climate change when several areas in the northern hemisphere most notably in Europe experienced extreme cold and ...
| Exp1 | Exp2 | Exp3 | Exp1 | Exp2 | Exp3 | |
12 | 18 | | | | | | | |
13 | 17 | | | | | | | |
14 | 16 | | | | | | | |
15 | 15 | | | | | | | |
16 | 14 | | | | | | | |
17 | 13 | | | | | | | |
18 | 12 | | | | | | | |
Results:
H2so4 (cm3) | NaOH(cm3) | Temperature (°C) | Temperature change (°C) | Average temperature change (°C)* |
| Exp1 | Exp2 | Exp3 | Exp1 | Exp2 | Exp3 | |
12 | 18 | 34 | 34 | 34 | -14 | -14 | -14 | -14 |
13 | 17 | 35 | 35 | 34 | -15 | -15 | -14 | -14.6 |
14 | 16 | 36 | 36 | 36 | -16 | -16 | -16 | -16 |
15 | 15 | 37 | 37 | 37 | -17 | -17 | -17 | -17 |
16 | 14 | 37 | 36 | 37 | -17 | -17 | -17 | -17 |
17 | 13 | 36 | 35 | 35 | -16 | -16 | -15 | -15.6 |
18 | 12 | 35 | 34 | 33 | -15 | -15 | -13 | -14.3 |
* Temperature change calculated initial temperature – final temperature.
* Start temperature = 20 °C
Energy Change:
Energy change (J) = m x s x t
Experiment 1 | Experiment 2 | Experiment 3 |
-1764 | -1764 | -1764 |
-1890 | -1890 | -1764 |
-2016 | -2016 | -2016 |
-2142 | -2142 | -2142 |
-2142 | -2142 | -2142 |
-2016 | -2016 | -1890 |
-1890 | -1890 | -1638 |
From my results I can see that the temperature increased until neutralisation occurred, after the point of neutralisation the temperature decreased showing an exothermic reaction. This is because there was no temperature change. My results show an exothermic reaction as heat was given off from the system (reaction mixture) to its surroundings (environment).
From the table I can see that neutralisation occurred at 15cm3 of sodium hydroxide and 15cm3 of sulphuric acid. I have used a smaller range for this experiment, as it will allow me to have a clear and precise idea at what volumes the sodium hydroxide and sulfuric acid have to be for neutralisation to occur. If the range were larger then I would not have a precise idea of when neutralisation occurs, as there would be a large difference between the intervals.
