Science Answer the questions.[Che-2M]

Impure metal M is made the anode, thin strips of pure metal M as cathode and a salt solution of metal M as electrolyte.

Iron and aluminium will displace hydrogen from dilute acids as they more reactive then hydrogen. Mercury and copper cannot displace hydrogen from dilute acids as they are less reactive than hydrogen.

Amphoteric oxides are the oxides, which react with both acids and bases to form salt and water.
E.g. ZnO and Al₂O₃.

Copper does not react with cold water, hot water, or steam. However, iron reacts with steam. If the hot water tanks are made of steel (an alloy of iron), then iron would react vigorously with the steam formed from hot water. 3Fe + 4H₂O → Fe₃O₄ + H₂O.
That is why copper is used to make hot water tanks, and not steel.

Aqua regia (By volume, this contains 3 parts of concentrated hydrochloric acid and 1 part of concentrated nitric acid) is the solution, which is used to sparkle the bangles like new, but their weight will be reduced drastically.

Carbonate and sulphide ores are usually converted into oxides during the process of extraction because metals can be easily extracted from their oxides rather than from their carbonates and sulphides.

Though aluminium is a highly reactive metal, it is resistant to corrosion. This is because aluminium reacts with oxygen present in air to form a thin layer of aluminium oxide. This oxide layer is very stable and prevents further reaction of aluminium with oxygen. Also, it is light in weight and a good conductor of heat. Hence, it is used to make cooking utensils.

Sodium, potassium, and lithium are very reactive metals and react very vigorously with air as well as water. Therefore, they are kept immersed in kerosene oil in order to prevent their contact with air and moisture.

When non-metals react with oxygen, they form acidic oxides or neutral oxides.
Example: Carbon reacts with oxygen to form an acidic oxide called carbon dioxide. Hydrogen reacts with oxygen.

Test tube A contains distilled water which is considered as soft water, free from ions like Mg²⁺, Ca²⁺, etc. So, in this case, the length of foam will be the longest(maximum).
Test tube B contains underground water which contains ions like Mg²⁺, Ca²⁺, etc. which react with soaps to form salts of fatty acids called scum, which are insoluble in water. So, in this case, the length of form will be the less in comparison to test tube A.
Test tube C contains distilled water with CaSO₄, which contains Ca²⁺ ions which react with soaps to form salts of fatty acids called scum, which are insoluble in water. So, in this case also, the length of foam will be the less in comparison to test tube A.

Solid air-fresheners are covalent compounds because they are volatile compounds with low melting and boiling points.

1. 3Fe (s) + 4H₂O (g) → Fe₃O₄ (aq) + 4H₂ (g)

2. Ca (s) + 2H₂O (I) → Ca(OH)₂ (aq) + H₂ (g) + Heat

2K (s) + 2H₂O (I) → 2KOH (aq) + H₂ (g) + Heat

Metal oxides are basic in nature and turn red litmus blue. For example: Magnesium oxide. Non-metal oxides are acidic or neutral in nature. The acidic oxides turn blue litmus red.
For example: Carbon dioxide.

White phosphorus is kept immersed in water because it reacts spontaneously with oxygen of air to form phosphorus pentoxide but does not react with water.

Sodium chloride has a high melting point because it is an ionic compound and these compounds are made of up of positive and negative ions. There is a strong force of attraction between the oppositely charged ions, so, a lot of heat energy is required to break this force of attraction and melt or boil the ionic compound.

These compounds are made up of positive and negative ions. There is a strong force of attraction between the oppositively charged ions, so a lot of heat energy is required to break this force of attraction and melt the ionic compounds. This is why ionic compounds have high melting points.

Gold ornaments look new even after several years of use because gold does not corrode when exposed to atmosphere. It is a highly unreactive metal which remains unaffected by air, water vapour and other gases in the atmosphere.

A new aluminium vessel lose shine so soon after use due to the corrosion of aluminium metal when exposed to moist air. This happens because the oxygen of air reacts with aluminium toform a thin, dull layer of aluminium oxide all over the vessel.

Aluminium does not corrode right through because aluminium is more reactive than iron and it forms a layer of aluminium oxide as soon as it comes in contact with moist air.
This aluminium oxide layer is very tough and prevents the aluminium underneath from corroding.

The metals like Na, K, Ca and Mg never found in their free state in nature because of the reason that all of these metals are high-up in the reactivity series. And just because they are so reactive, they are never found in nature as free elements.

Ionic compounds are usually hard because ther held together by strong electrostatic forces of attraction. Therefore the oppositely charged ions pack tightly with each other and form a crystalline structure which is very hard to break down.

An aqueous solution of an ionic compound conducts electricity because there are plenty of free ions in the solution which are able to conduct electric current.

Al metal cannot be obtained by the reduction of Al₂O₃ with Coke (C) because Al has more affinity for oxygen than carbon. So, carbon cannot remove oxygen from Al₂O₃ and thus cannot convert Al₂O₃ into Al.

The compounds that can conduct electricity in molten state are: KCl, CaCl₂ Because they are ionic compounds and will completely dissociate their ions in water.

Conduct electricity: MgCl₂ , NaCl, Na₂S (Ionic compounds)
Do not con duct electricity: CCl₄ , CS₂ ( Covalent compounds).

Reaction (a) will not occur because Cu is less reactive than Mg.
Reaction (c) will also not occur because Fe is less reactive than Mg.

Silver metal when exposed to the hydrogen sulphide turns blackish grey. It is because it consequently reacts with the gas and forms silver sulphide. Due to the traces of H₂S in the air, this sulphide layer is formed thus turning the silvery and shiny grey colour into black or grey.

Hydrogen gas is evolved when dilute hydrochloric acid is added to a reactive metal. When iron reacts with dilute H₂SO₄, iron (II) sulphate with the evolution of hydrogen gas is formed.
Fe_(s) + H₂SO_4(aq) → FeSO_4(aq) + H_2(g)

When zinc is added to iron (II) sulphate then it will displace the iron from iron sulphate solution as shown in the following chemical reaction. Zn (s) + FeSO₄ (aq) → ZnSO₄ (aq) + Fe (s)

When metals combine with oxygen, they form basic oxides.
Example: Sodium reacts with oxygen to form a basic oxide called sodium oxide.

The special quality of iron pillar near Qutub Minar is that it has not rusted till now. it was made 1000 of years ago in the time of Ashoka.

The arrangement of metals in a vertical column in the order of decreasing reactivities is called reactivity series.
Increasing order of reactivity: Iron < zinc < magnesium < sodium

Before extracting metal from an ore, it is necessary to remove these impurities (gangue) from it. By removing the gangue, we get a concentrated ore containing a much higher percentage of metal. This is called concentration of ore; also known as enrichment of ore.

Metals are malleable i.e. they can be beaten into thin sheets with a hammer.
Example: Aluminium.
Metals are ductile i.e. they can be drawn into thin wires.
Example: Copper.

Corrosion is General destruction of metals due to chemical reaction with water and oxygen. Prevention can be through oiling and Greasing.

The process of thickening of aluminium oxide layer on the surface of aluminium objects by electrolysis is called anodizing. It is done to provide more protection to the aluminium object from corrosion.

It means that 22 parts pure gold is alloyed with 2 parts of either silver or copper for making ornaments; Silver and copper are usually alloyed with gold to make it harder.

The process of depositing a thin layer of zinc metal on iron objects is called galvanisation. It is done by dipping iron object inmolten zinc metal.

It is the process of refining of metal in which impure metal is made the anode and a thin strip of pure metal is made the cathode. A solution of metal salt is used as an electrolyte.

The chemical bond formed by the transfer of electrons from one atom to another is known as an ionic bond.
Covalent bond is present in an oxygen molecule.