Control
As this experiment is about varying acid concentration, there is no need to keep it constant.
To control the mass of chips, I will use the same mass for every experiment I do. This will be 10g of marble chips
As long as the experiment is done at room temperature, the temperature should be constant at around 23º
The volume of acid is constant by using the exactly 25cm³ of acid for every experiment.
As the size of chips come in different sizes, I will use a sieve to filter the sizes out. And to use the came size through out the whole experiment.
Basic experiment
This experiment is going to see how much gas is produced when a certain amount of chips are reacted with acid. The gas is going to be measured by a gas syringe.
Method
Before anything happens, I will need to see what the room temperature is at that day, using a thermometer
I will take out a conical flask and put exactly 10g of marble chips using an electrical balance to measure it out. A Polystyrene boat will be used to hold the chips while measuring on the balance. This extra weight will be zeroed off at the beginning of the weighting. A clamp stand will then be set up, clamping a gas syringe lightly. It has to be lightly because if it were too tight, the syringe would not be able to move freely. The nozzle of the syringe will be fitted with a glass tube feeding into a rubber bung, which will fit perfectly on top of the flask.
Different concentrations of the acid will be made, as the total amount of liquid will be 25cm³,
The 1st experiment will be of 25cm³ of acid and 0cm³ of water – 2 moles
2nd. 20cm³ of acid and 5cm³ of water – 1.6 moles
3rd .15cm³ of acid and 10cm³ of water – 1.2 moles
4th. 10cm³ of acid and 15cm³ of water – 0.8 moles
5th. 5cm³ of acid and 20cm³ of water – 0.4 moles
For a control experiment there should be 0cm³ of acid and 25cm³ of water, a total of 0 moles of acid. This is to see that water does not increase the concentration of the acid.
Using the measuring cylinder, I carefully measure out the different amounts to acid and water. These different solutions will be reacted with the marble chips in 5 different experiments.
The chips are firstly place in the conical flask. When the acid is added to the chips, I will have to close the flask quickly, or there will be gas lose, meaning inaccurate readings. The syringe will collect the gas produced; the plunger moves backwards to show how much gas is produced.
A stopwatch would also be useful because every 10 seconds a reading will be made by reading the scale of the gas syringe. The result will be written down onto paper.
The experiment stops when either, the gas produced goes over the scale of 100 cm³ or if the gas produced is too slow, and has taken more than 4 minutes.
After each reaction, the acid needs to be poured down the sink and the marble chips disposed if correctly
The whole experiment should be repeated twice to get an average, and also try to correct anomalous points.
Predictions
Due to the collision theory, concentration is the number of particles of reagents in a fixed volume. If the concentration increases, there are more particles to collide with other reagents per second. This means more collisions per second thus increasing the rate of reaction. If concentration decreases, the opposite will happen and slower rate of reaction.
My predictions (which follows the prediction) of this experiment are that, the stronger the concentration of that acid, the faster the rate of reaction is, meaning more gas loss. Because a preliminary experiment was done 1 week in advance, the acid with 2-moles/ dm³ produced 100 cm³ in less than 30 seconds. When there is 20cm³ of water and 5cm³ of acid, the experiment will take more than 5 minutes to complete, because the acid it far too weak to react all the marble chips.
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Equipment
Clamp stand – to hold the gas syringe
Conical flask – for the reaction to take place
Beaker – to contain the acid
Measuring cylinder – to measure out the acid
Thermometer – to find out the room temperature at the start
Gas syringe – to contain and measure how much gas
Bung with glass tube – To feed the gas produced into the gas syringe
Stopwatch – to see the time when taking down results
Scales – to measure out the marble chips
Polythene boat – to hold the chips while measured.
Marble chips and dilute acid- for the experiment
Safety
Safety goggles need to be worn at all times, because the acid fizzes and bubbles. Some of the liquid might get flicked into anyone’s eyes; acid is corrosive, especially towards our bodies.
Table of results
The results will be put into a table:
Gas loss in cm³
Sources of information
A basic knowledge of the collision theory and rate of reactions. Also backed up by
Chemistry by Elleen Ramsdeen
