Effect of concentration on reaction rate Flashcards Preview

Chemistry - New > Effect of concentration on reaction rate > Flashcards

Flashcards in Effect of concentration on reaction rate Deck (19):

Identify the pale yellow precipitate that obscures the cross on the sheet of paper

Colloidal sulfur


Describe the procedure for preparing the 0.08M solution of sodium thiosulfate from the 0.10M solution

0.1 = 100 cm3
Add 80cm3 of solution using burette
Make up until 100cm3 with deionised water


Explain why the reciprocal of time [1/time] is used as a measure of the initial rate of the reaction?

Rate of reaction is inversely promotional to the time. When time increases, there is a decrease in rate


Why are the concentration and the volume of HCL solution kept constant?

So that there is only one variable that changes - ensures fair experiment


Outline the experimental procedures you would follow in order to show the effect of concentration on reaction rate

Place a conical flask on a piece of paper marked with an X
Place fixed volume of a given concentration of thiosulfate in the flask
Add fixed volume of HCL to the flask and note the time taken for sulfur to obscure x, swirl conical flask, reaction is finished
Rate of reaction for concentration is inversely promotional to the time taken
Repeat the experiment with different concentrations


State the relationship between the rate of the reaction and the concentration of sodium thiosulfate

The rate of reaction is directly propotional to the concentration of the thiosulfate.


Explain why the rate of reaction increases with thiosulfate concentration

Increased concentration of thio means more molecules in a given molecule therefore more successful collisions and thus increase in rate of reaction


Describe a method you could use to determine when the same mass of sulfur had been formed in each run

X on a piece of Paper which ensures a fair test
When it’s no longer seen, sulfur has precipitated and shows same amount


If you were given sodium thiosulfate solutions of the following concentrations : 0.04M, 0.08M, 0.12M and 0.16M, describe how you would show that the rate of reaction is directly proportional to the concentration of sodium thiosulfate

-do method
-find 1/t
-plot vs concentration


What is meant by the term concentration?

Amount of solute that is dissolved in a given volume of solution


What is the purpose of placing a mark on the paper?

The X serves as a standard marker that helps us determine the stage at which the same amount of sulfur has precipitated for each experiment and ensures it is a 'fair test'


Describe the appearance of the suspension formed

Cloudy (milky) yellow colour


Apart from the element causing the yellow suspension, what other products are formed in this reaction?

Sodium chloride, sulfur dioxide and water


Why must the flask and graduated cylinder be rinsed out after each reading?

To avoid contamination of the next set of solutions from the previous experiment i.e ensure droplets of previous solutions do not alter concentrations


What happened to the rate of reaction as the concentration was decreased?

The rate also decreased


Time and rate are said to be inversely proportional, explain what this means

As time is increased, the rate is decreased i.e the longer the time it takes the cross to be obscured, the slower is the rate of reaction


What is the relationship between time and rate?

Inversely proportional, as time increases the rate is decreased


Give the balanced equation for the reaction

2HCL + Na2S2O3 -> 2Nacl + SO2 + S(down) +H20


Describe a procedure for diluting the 0.20 M sodium thiosulfate solution to give 50 cm3 of a 0.12 M solution.

(.20/.12= 5/3. 50 / 5/3 = 30)
Measure 30 cm3 of the 0.20 M thiosulfate solution dilute (make up) to 50 cm3 using deionised water