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(a) What is produced if an acid is added to a base?
(b) Why does dry HCl gas not change the colour of dry litmus paper?
(c) What colour does phenolphthalein indicator turn when added to an alkali (such as sodium hydroxide)?
(a) Salt and water are produced when acid is added to the base.
The equation can be written as:
$NaOH(aq) + HCl(aq) → NaCl(aq) + H_2O(l)$
Base + Acid → Salt + Water
(b) Dry HCl does not change the colour of dry litmus paper because dry HCl does not undergo dissociation to form ions as there is an absence of an aqueous medium. The colour of the litmus paper changes only when the ions are formed. Hence it does not change the colour of litmus paper
(c) Phenolphthalein indicator turns pink from colourless when added to an alkali like sodium hydroxide.
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