Concentration & Reaction Rate in Sodium Thiosulphate

Introduction: We are trying to find out how the rate of reaction is affected by the concentration of one of the reactants. We are investigating this with sodium thiosulphate and hydrochloric acid. We will use different strengths of HCI acid and record the results. Method:  Collect the apparatus.  Make up different concentrations of hydrochloric acid using table 1.  Measure 20cm3 of sodium thiosulphate and pour into conical flask  Draw "X" on paper and place under conical flask. Carefully pour hydrochloric acid into burette using funnel.

  Remove funnel.

Turn the tap on the burette and start the stop-clock  Stop the clock when the "X" is no longer visible.  Record the results and repeat x5. Repeat for 0. 5m and 1. 0m. How to make up the different concentrations of hydrochloric acid. Apparatus Conical flask 6 beakers Clamp stand Burette Stop clocks Sodium Thiosulphate Different concentrations of HCI acid. Table 2 Concentration of acid (M) Volume of water (ml) Volume of HCI acid (ml)0 What is a reaction? A reaction occurs when two reactants successfully react together to form a new product.

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This is called the collision theory. There is many different ways to measure the rate of reaction.  These include: Measuring the amount of gas produced  Weighing before and after the experiment Draw an X on a piece of paper and measure how long it takes for the substance to turn cloudy enough so that the X is no longer visible  Using sensors to detect the loss of the starting material or the formation of the product Variables: Temperature: If the temperature is high, the particles have more energy.

As a result of them having more energy they move a lot faster.

Therefore the particles collide a lot faster increasing the rate of reaction and making a new product. Examples of reactions: An example of a reaction is when water and iron combine together to form iron oxide (H2O) (Fe 3) (Fe2 O3) Another example of a reaction is when zinc and oxygen combine together to form zinc oxide (Zn) (O2) (Zn O2) Concentration: If the concentration is greater so to is the number of particles. When you increase the number of particles you increase the chance of a collision, and the chance of them reacting to form a new product. Surface area:

The smaller the particles the greater the surface area. Therefore there is a greater chance of them colliding as there is more area for them to hit off. Therefore the smaller the particles the greater the rate of reaction. Catalyst: A catalyst is a substance, which speeds up the rate of a reaction, without being used up itself. Catalysts work better when the particles are smaller because the surface area is greater. Prediction: I think that the high the concentration the faster the rate of reaction. This is because there is more H+ ions so the higher the chance of colliding.

Therefore the quicker the reaction. Diagram These are the results I recorded: Concentration of acid (M)  Conclusion: From my results I can conclude that concentration does affect the rate dramatically. For example if we compare strongest strength of acid (1 molar) to the weakest (0.2 molar), there is a difference of nearly 14 seconds between the averages. This is because in the 0. 2 molar acid there is only a small amount of h+ ions where as in the 1 molar acid there is a lot more.

Therefore the collisions occur a lot faster and the rate of reaction is increased as illustrated in the diagram above. Science coursework Stephen bannon Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.