Chemistry Questions and Answers

C = 72 / 12       H = 12 / 1       O = 16 / 16

C = 6               H = 12             O = 1

: EMPIRICAL FORMULA

C$_6$H$_12$O

- Iron sulfide reacts with hydrochloric acid, releasing hydrogen sulfide: FeS + 2HCl → FeCl$_2$ + H$_2$S.

- Hydrogen sulfide reacts with lead acetate to form lead sulfide and thus produces a coloration on the paper which will vary from yellow to black, depending upon the amount of hydrogen sulfide present.

-Potassium dichromate solution is acidified with dilute sulphuric acid to oxidise ethanol into ethanoic acid.

- Endothermic reactions are chemical reactions in which the reactants absorb heat energy from the surroundings to form products.

-  A system of reactants that absorbs heat from the surroundings in an endothermic reaction has a positive ΔH.

-  examples of endothermic processes:

• Melting ice cubes.
• Melting solid salts.
• Sublimation of dry ice into carbon dioxide gas.
• Evaporating liquid water.

- When quicklime is added to water, it forms slaked lime along with the evolution of heat. There will be a rise in the temperature of the bucket. Calcium oxide reacts with water to form calcium hydroxide, also called slaked lime.

- That is adding water to quicklime produces an exothermic reaction (gives out heat) and hydrated lime.