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(i) It keeps on burning.
(ii) It gets extinguished.
(iii) Although CO2 is a non-supporter of combustion, but burning magnesium

breaks CO2, into Carbon and Oxygen; Oxygen helps in burning.
(iv) CO2 is a supporter of combustion.

a) (ii) b) (i) and (iii) c) (i) and (iv) d) (i)
4. pH is measured using a pH meter, which comprises a detecting unit consisting of
a pH sensitive glass electrode and an indicating unit which indicates the pH as
shown below.

To measure the pH of a solution, the glass electrode is dipped into the solution and
the pH is displayed on the screen of the indicating unit. Before measuring the pH of
another solution, the glass electrode is rinsed with distilled water and dried
carefully with tissue paper.
How is the pH reading of the second solution likely to be affected if the glass
electrode is not dried with tissue paper in the following cases:-