In this experiment I had to put different amounts of substances into the Conical Flask. And using a timer, see how long it took before the reaction took place.
This diagram shows the Conical flask and a black cross underneath it. We were hoping that as a result of a chemical reaction the liquid within the beaker would be that we were unable to see the black cross at the bottom of the flask This result would mean that the solution had either changed colour or become cloudy. We tried and tested this experiment three times and recorded each set of results for the sake of integrity.
My Method for the trials
- Take three different molars of acid; 0.5, 1 and 2.
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Measure 5cm3 of 0.5 molar hydrochloric acid and 25cm3 of sodium Thiosulphate
- Place the conical flask on top of a piece of paper with an ‘x’ drawn on it.
- Pour in the hydrochloric acid and sodium Thiosulphate.
- Swirl the flask gently and start the timer
- Observe the amount of time taken for ‘x’ to disappear.
- Record times in a table of results.
My Prediction
I predict that as the temperature is increased the rate of reaction will increase. I also predict that as the concentration of the sodium Thiosulphate increases the rate of reaction will increase. This means that both graphs drawn up in my analysis will have positive correlation, and will probably be curved as the increase in rate of reaction will not be exactly the same as the concentration\temperature is increased. This can be justified by relating to the collision theory. When the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully. If solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur. However, not all collisions bring about a reaction. A reaction will only occur if the colliding particles possess more than a certain minimum amount of energy. This is known as the activation energy. This activation energy will enable the chemical bonds that already exist between the particles to stretch and eventually break, and atoms, ions and electrons will be rearranged.
There are factors that affect this experiment such as temperature, concentration and time. I do not think that surface area will affect the experiment, as both chemicals are liquids.
All this can be understood better with full understanding of the collision theory itself.
My Evaluation
Looking at my results, the table and the line graph that I have produced, the results appear to be very similar showing ,that the experiment I did was a fair one. Also looking at my graph there is a positive correlation. Even a minor mistake, can cause acute changes in the results. I also noticed that the lower the concentration of Thiosulphate and the higher amount of water being used to dilute the Thiosulphate meant that it took longer for a chemical reaction to take place.
The scientific Analysis of the Experiment
By using a higher concentration of Thiosulphate and less water it meant that the black X underneath the Conical flask disappeared more rapidly, this is because there are more particles in the substance enabling it to react faster. All particles are made up of particles, and the particle I was using in the experiment was molecules, which are a group of 2 are more atoms bonded together. To get a chemical reaction, as mine did the particles, must collide together (crash). As you increase the concentration of the acid(Thiosulphate) there are more acid particles in the same volume. Therefore there is a greater chance of it colliding, and reacting with particles. You are increasing the rate of reaction. The reason for the water changing to be cloudy is that we get a Precipitate of Sulphur (Thiosulphate) as the solutions react.
