For kinetic study of the reaction of iodide ion with ${\mathrm{H}}_2{\mathrm{O}}_2$ at room temperature :

(A) Always use freshly prepared starch solution.

(B) Always keep the concentration of sodium thiosulphate solution less than that of $\mathrm{KI}$ solution.

(C) Record the time immediately after the appearance of blue colour.

(D) Record the time immediately before the appearance of blue colour.

(E) Always keep the concentration of sodium thiosulphate solution more than that of $\mathrm{KI}$ solution.

Choose the correct answer from the options given below

For kinetic study of the reaction of iodide ion with ${\mathrm{H}}_2{\mathrm{O}}_2$ at room temperature following Precautions needs to be used.

• Always keep the concentration of sodium thiosulphate solution less than that of potassium iodide solution.
• Always use freshly prepared starch solution.
• Use fresh samples of hydrogen peroxide and potassium iodide.
• Always use the same measuring cylinders for measuring solutions in two different sets of observations. If after measuring one solution, the cylinder is used for measuring another solution, clean it before using.
• Record the time immediately after the appearance of blue colour.

So, among the given statements only the statement $\left(\mathrm{A}\right), \left(\mathrm{B}\right), \mathrm{and} \left(\mathrm{C}\right)$ are correct.