(a) Define indicator. Name two indicators obtained from plants. |
(b) Write balanced chemical equation for the reaction that takes place when sodium oxide reacts with water. How will this solution behave towards phenolphthalein and red litmus paper? |
(c) State what happen when sodium hydroxide, solution reacts with dilute hydrochloric acid. What is this reaction called? |
Answer:
(a) Indicator is any substance that gives visible sign, usually by colour change, of the presence or absence of a chemical species. Two indicators are litmus and turmeric. (b) \[N{{a}_{2}}O+{{H}_{2}}O\to 2NaOH\] NaOH in phenolphthalein shows pink colour and turns red litmus blue. (c)\[NaOH + HCl \left( dil. \right)\to NaCl+{{H}_{2}}O\] . This is a neutralisation reaction where add acid base reacts to give salt and water.
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