Question: Give composition of the alloy – ‘brass’ and ‘bronze’.
Answer: Brass – Cu and Zn
Bronze – Cu and Tin
Question: What is the formula of rust?
Question: An alloy has low melting point and is, therefore, used for electrical fuse. Name they alloy and write its constituents.
Answer: Solder, Pb and Sn.
Question: Name one metal and a non-metal found in liquid state at room temperature.
Answer: Metal – mercury.
Non-metal – bromine.
Question: Name two metals which react with dilute HNO3 to evolve H2 gas.
Answer: Magnesium (Mg) and manganese (Mn).
Question: Why oxides of high reactive metals cannot be reduced by carbon?
Answer: This is because these metals have more affinity for oxygen than carbon.
Question: What is formed when sodium absorbs moisture from air? Give equation also.
Answer: It forms sodium hydroxide.
2Na + H2O → 2NaOH + H2
Question: Why the sulphide and carbonate ores are converted into oxides?
Answer: It is because it is easier to obtain a metal from its oxide, as compared to its sulphide and carbonates.
Question: From amongst the metals sodium, calcium, aluminium, copper and magnesium, name the metal:
(i) which reacts with water only on boiling, and
(ii) another which does not react even with steam.
Answer: (i) Magnesium (ii) Copper.
Question: Name any one metal which reacts neither with cold water nor with hot water but heated steam to produce hydrogen gas.
Answer: Iron (Fe), aluminium (Al) and zinc (Zn) do not react either with cold or hot water. They react with steam to from metal oxide and hydrogen, e.g.,
3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
Question: Name two metals which have very low melting point.
Answer: (i) Caesium (ii) Gallium.
Question: Name is a non-metal which is lustrous and a metal which is non-lustrous.
Answer: Iodine is a non-metal which is lustrous. Iron is a metal which is non-lustrous.
Question: Write balanced chemical equation for the reaction: Aluminium when heated in air. Write the name of the product.
4Al + 3O2 → 2Al2O3 (Aluminium oxide)
Question: Why do ionic compounds electricity in the solid state.
Answer: Movement of ions in the solid state is not possible due to their rigid structure.