Q8 of 41 Page 1

A shiny brown coloured element X on heating in the air becomes black in colour. Name the element X and the black coloured compound formed.

The unknown element X is copper (Cu). When copper is heated in air, it forms a black coloured compound called copper oxide (CuO). The reaction for above chemical change is given below:

More from this chapter

All 41 →
6

Why respiration is considered an exothermic reaction? Explain.

 7

In the refining of silver, the recovery of silver from silver nitrate solution involved "displacement by copper metal. Write down the reaction involved.

 9

A solution of substance X is used for white washing.

(i) Name the substance X and write its formula.


(ii) Write the reaction of the substance X named in (i) above with water.

 10

Why does the colour of copper sulphate solution change when an iron nail is dipped in it?