Question

(i). Tooth enamel is one of the hardest known substance in our body. How does it

undergo damage due to the eating of chocolates and sweets? What should be done to

prevent it?

(ii). Dry HCl gas doesn't change the colour of the dry blue litmus paper. Explain.

(iii). Alcohol and glucose also contain hydrogen but don't conduct electricity. Explain.

(iv). A compound 'X' on reaction with an acid produces a colourless gas which when

bubbled through lime water turns it milky. This compound 'X' is also used in soda acid

fire extinguisher. Identify 'X' and write its reaction with acid.​

Answer 1

Answer:

i) When the pH in the mouth is below 5.5, bacteria present in the mouth produce acids by degradation of sugar and corrode the tooth enamel. It can be prevented by using tooth pastes which are generally basic.

ii) Dry HCL it does not dissociate to give H+ ions. Acids dissociate to give ions only in the aqueous solution. In this, HCL is not in the aqueous form nor the litmus paper is wet, so the colour of the litmus paper does not change.

iii) The aqueous solution of glucose and alcohol do not show acidic character because these do not ionise to give hydrogen ions on dissolving in water. Hence, they do not conduct electricity.

iv) When acid reacts with metal carbonate or bicarbonate gives CO2​ gas which is colourless and odourless gas and turn lime water milky

Metal carbonate+CH3​COOH→salt+CO2​

CH3​COOH+CH3​OHConc.H2​SO4​

​esterCH3​COOCH3​​+H2​O

Methyl ethanoate, sweet smell.

Hope it helps you!