Metals And Non-Metals - MCQ Test (22-11-2017) - Class 10 MCQ

Pyrolusite is a mineral consisting essentially of manganese dioxide (MnO₂). It is an important ore of manganese. It is a black, amorphous mineral, often with a granular, fibrous or columnar structure.

Nitrogen prevents oxidation of dried fruits. It is used to prevent rancidity.

The difficulty of separating aluminium from oxygen in the alumina is overcome by the use of cryolite as a flux to dissolve the oxide mineral. Pure cryolite melts at 1012°C. It dissolves the aluminium oxides sufficiently well to allow easy extraction of the aluminium by electrolysis.

Calcium reacts with cold water (less violently as compared to the reaction of sodium with water) to form calcium hydroxide and hydrogen gas. Bubbles of hydrogen gas formed during the reaction stick to the surface of calcium and calcium pieces start floating in the water.

Platinum (Pt), Gold (Au) and Silver (Ag) occur in their free or native state.

Product X in the reaction indicates phosphine (IUPAC name: phosphane). The other product is sodium hypophosphite.

Highly reactive metals like Potassium, Sodium (Na), Calcium (Ca), Aluminium and Magnesium are obtained by electrolysis of their chlorides in molten state. They cannot be extracted by reducing their oxides with carbon. Iron (Fe) can be obtained from its oxide ore by reduction with coke or aluminium powder. Copper (Cu) can be obtained by heating its sulphide ore in air.

This reaction is an example of thermite process (also known as the Goldschmidt process). When aluminum powder reacts with iron oxide, a large amount of heat is released and a temperature of about 3500°C is attained which is enough to weld broken metallic parts.

Silver has the highest thermal conductivity amongst the elements. Although it is the best conductor, copper and gold are used more often in electrical applications because copper is less expensive and gold has a much higher corrosion resistance.

Sodium reacts vigorously with water. Such is the reaction that it has to be stored under kerosene. Calcium can react with cold water. Magnesium reacts with hot water. Heated iron reacts with water when hot steam is passed over it.

3Fe (s) + 4H₂O (g) → Fe₃O₄ (s) + 4H₂ (g)

Metals exhibit electrical conductivity (due to free electrons), sonority (production of ringing sound when struck) and ductility (ability to be drawn into wires).

Chemical reduction is used for enrichment of oxide ores. Hydraulic washing, Magnetic separation and Froth floatation method are used for the concentration of an ore. Hydraulic washing is based on the differences in gravities of the ore and the gangue particles. Froth floatation process is a process employed for the concentration or enrichment of a sulphide ore.

Aluminium is the reducing agent in the reaction. It reduces manganese dioxide (MnO₂) to manganese (Mn) and itself gets oxidised to aluminium oxide. Manganese dioxide acts as an oxidising agent.

The ammonia fountain demonstrates the solubility of ammonia in water. 

Carbon is a tetravalent element and does not lose or gain electrons easily to form electrovalent bonds. It forms covalent bonds with other elements.

Solder is a fusible metal alloy used to join metals for electrical work. Soldering differs from welding in that soldering does not involve melting the work pieces.

The Iron pillar near the Qutub Minar in Delhi is prevented from rusting because of the formation of magnetic oxide of iron (Fe₃O₄) on the surface. It is also painted with a mixture of different salts.

Most metals form basic oxides. However, some metals like aluminium and zinc, are amphoteric and form basic as well as acidic oxides. Non-metals react with oxygen to form acidic oxides or neutral oxides. E.g. Hydrogen forms a neutral oxide - H₂O.

Metals are alloyed to improve the properties of metals. An alloy is a homogeneous mixture of two or more metals. They are stronger, harder and more resistant to corrosion. They have a lower melting point and lower thermal conductivity than that of the constituent metals.

Hydrated copper sulphate (CuSO₄) is blue in colour. When water is then added to anhydrous copper sulphate, it turns into the pentahydrate form, acquiring a blue color, and is commonly known as blue vitriol.

The ratio of HCl and HNO₃ in Aqua Regia is 3 : 1. Aqua regia is a yellow-orange fuming liquid, so named by alchemists because it can dissolve the noble metals - gold and platinum.

The element is Sulphur. Sulphur is used to manufacture sulphuric acid and in the vulcanisation of rubber. S + 2HNO₃ → H₂SO₄ + 2NO

An acidic oxide will turn blue litmus red. Non-metal oxides (Oxides of S and N) are acidic in nature. Metal oxides (Oxides of Mg and Na) are basic in nature.

Galvanisation is the process of applying a protective coating of zinc to iron to prevent the rusting of iron. The most common method is hot dip galvanizing, in which steel sections are submerged in a bath of molten zinc.

Gold and Silver do not react with oxygen. They are less reactive metals and lie at the bottom of the reactivity series.

Alloys have lower electrical conductivity than that of pure metals. Alloys have lower melting points than that of the constituent metals. Different metals have different reactivity with water and dilute acids. Sodium and potassium react vigorously with cold water. Some metals like magnesium and calcium react with water to form metal hydroxide and hydrogen while some like aluminium and iron react with steam to form metal oxide and hydrogen. Metals usually displace hydrogen from dilute acids; some react only on heating. Metals like gold, silver and copper do not react with dilute acids at all.

The Iron pillar at Delhi was manufactured by the forge welding of pieces of wrought iron.

Roasting and Calcination are used for conversion of ore to metal oxide. Hydraulic washing, Froth floatation and Electromagnetic separation are used for concentration, dressing or benefaction of an ore. 

Sulphide ores are concentrated by froth floatation method. Collectors and froth stabilisers are added to a suspension of powdered ore in water. Light froth carrying mineral particles are skimmed off and then dried to recover ore particles.