CBSE CHEMISTRY

CHEMISTRY 1 MARKS Formation of compost is what type of reaction ? What happens when common salt is heated with sulphuric acid? Aluminum burns in chlorine to form aluminum chloride ? Write equations ? Heated iron metal reacts with steam to form iron (2) oxide and hydrogen ? Give an example of thermal decomposition ? What happens when gypsum is heated at 473 K ? A shiny brown coloured element X on heating in air becomes black in colour . Name the element X and the black colored compound formed ? What are olfactory indicators? What happens when zinc is hydrolyzed? 2 MARKS Why the silver articles tarnish ? What do you mean by precipitation reactions ? Explain the colour changes when copper sulphate solution is put in a iron container ? What is dilution in terms of ions concentration ? Explain the displacement reactions between lead and copper chloride with the help of a chemical reactions ? Why should be the magnesium ribbon be cleaned before burning ? What are redox reactions ? explain with an example ? what happens when silver chloride is exposed to sunlight ? How does black and white photography takes place ? Explain wth the help of a equation ? What happens when silver nitrate solution is added to sodium chloride solution ? explain with a chemical equation ? How do corrosion become advantageous in the case of aluminum ? Why does the medal of bronze turn green in moist conditions ? What happens when copper reacts with silver nitrate solution ? What is Rancidity? How it can be protected ? A green colored crystals are heated to form 2 gases X and Y which causes nausea and irritation in eyes. Identify the gases and write relevant chemical equations? sodium bicarbonate is a salt, still it is used as antacid. Why 3 Marks Brine solution is neutral. On electrolysis of brine solution, two gases are evolved at two different electrodes and the solution turns red litmus blue. What does it indicate? Name the two gases which are formed on these electrodes. Why the nature of solution changes after electrolysis? What is this process called? Write the balanced chemical equation for the reaction. A farmer could not increase his yield despite of lots of efforts .When he got tested the pH of soil, he found that the pH of soil is 3. What will you suggest to improve the yield of the field?