Free Practice Questions for Chemistry in General-studies

 Sulfur and Phosphorus non-metal are used in firecrackers

Important Points : 

• Sulfur is a non-metal with the chemical symbol S and atomic number 16. It is used in the production of sulfur dioxide, sulphuric acid, Carbon disulfide, etc. It is used in the manufacture of matches, and explosives. It is used as a fungicide. It is used in the vulcanization of rubber.

Sodium

• It is a metal with the atomic number 11.
• It is so soft that it can be cut with a knife.
• It is used as a reducing agent.
• It is used in the making of tetraethyl lead compound by the use of an alloy of sodium-lead.
• Sodium metal is very reactive. It reacts vigorously with oxygen and water. A lot of heat is generated in the reaction. It is, therefore, stored in kerosene.

Copper

• Copper is used for making wires used in electrical industry and for water and steam pipes because it is a good conductor of heat and electricity. 
• It is also used in several alloys e.g., brass (with zinc), bronze (with tin) and coinage alloy (with nickel).

Zinc

• It is a transition element.
• Zinc is used for galvanizing iron. 
• It is a constituent of many alloys, e.g., brass, (Cu 60%, Zn 40%) and german silver (Cu 25-30%, Zn 25-30%, Ni 40–50%).

Metals combine with oxygen to form basic oxides.

Important Points:

• Aluminium oxide and zinc oxide show the properties of both basic as well as acidic oxides. These oxides are known as amphoteric oxides. 
• Metals are malleable and ductile.
• Metals are good conductors of heat and electricity.
• Metals are generally hard. Alkali metals (lithium, sodium, potassium) are so soft that they can be cut with a knife.

₁₉K⁴⁰ and ₁₈Ar⁴⁰ are isobars.

Important Points:

• Atoms of different elements with different atomic numbers, which have the same mass number, are known as isobars. 
• Potassium(K), atomic number 19, and argon (Ar), atomic number 18 have different number of electrons, but same mass number that is 40.

Option Explanation:

Nitrogen is a non-metal. It does not show allotropy.

Important Points:

• Nitrogen atom has two stable isotopes: ¹⁴N and ¹⁵N. 
• Nitrogen gas is slightly lighter than air and slightly soluble in water. 
• It is non -flammable. 
• Nitrogen is used to make ammonia which is used for making fertilizers.

Methane gas is released from the paddy fields.

Important Points:

• The first member of the family of alkanes is methane.
• It has the molecular formula CH4. This hydrocarbon is saturated.
• Marsh gas is another name for it.
• Methane is a greenhouse gas. It is the primary ingredient of natural gas.

Iodine is the lustrous non-metal.

Important Points:

• Nonmetals have no malleability or ductility. Except for Iodine, they are non-lustrous.
• Except for bromine, which is a liquid, nonmetals are either solids or gases.
• Except for graphite, they are poor conductors of heat and electricity. 
• Except for mercury, which is a liquid at room temperature, they are all solids at room temperature. 
• The hardest known natural substance is diamond, which also has the highest known melting and boiling points. It is an allotrope of carbon.

Pristley and Scheele .

Important Points :

Oxygen

• Oxygen was discovered by Joseph Priestley, Antoine Lavoisier and Carl Wilhelm Scheele. Oxygen is the most abundant of all the elements on earth.
• Oxygen is the third most abundant element in the universe and makes up nearly 21% of the earth's atmosphere. Oxygen exists as diatomic molecule (O₂). 
• Dioxygen is a colourless and odourless gas.  Oxygen atom has three stable isotopes: ¹⁶O, ¹⁷O and ¹⁸O. Molecular oxygen, O₂ is unique in being paramagnetic inspite of having even number of electrons.
• Oxygen cylinders are widely used in hospitals, high altitude flying and in mountaineering. In addition to its importance in normal respiration and combustion processes, oxygen is used in oxyacetylene welding.

Options Explanation : 

Neon has 10 electrons, while Mg2+ has 10 protons but only 8 electrons.

Important Points:

• Isoelectronic elements are elements that have the same number of electrons.
• Neon has 10 electrons, which is a stable electron configuration.
• Oxygen has 8 electrons, but when it gains 2 electrons, it becomes O2-, which also has 10 electrons.
• Fluorine has 9 electrons, but when it gains 1 electron, it becomes F-, which also has 10 electrons.
• Sodium has 11 electrons, but when it loses 1 electron, it becomes Na+, which has 10 electrons.
• Magnesium has 12 electrons, but when it loses 2 electrons, it becomes Mg2+, which has 10 electrons.
• Therefore, the only element that is not isoelectronic with neon is Mg2+.

Bronze contains copper and tin, while solder contains tin and lead.

Important Points:

• Bronze is an alloy of copper and tin. It is typically made up of 80% copper and 20% tin, but the proportions can vary depending on the desired properties.
• Solder is an alloy of tin and lead. It is typically made up of 60% tin and 40% lead, but the proportions can vary depending on the desired properties.
• The main difference between bronze and solder is the addition of lead in solder. Lead makes solder more easily melted and workable, which makes it ideal for welding electrical wires together.
• Bronze is a stronger and more durable alloy than solder, which makes it ideal for making medals and other objects that need to be strong and resist wear and tear.

Baking soda is an ingredient of baking powder.

Important Points:

• Sodium chloride is one of the raw components used in the manufacturing of baking soda.
• To make delicious, crispy pakoras and other foods, baking soda is frequently used in kitchen recipes.
• It is included to speed up cooking.
• It is a component of baking powder, which is made up of baking soda and tartaric acid, a moderate acid.
• Antacids also contain sodium hydrogen carbonate as a component.
• It relieves discomfort by neutralising excess stomach acid due to its alkaline nature.
• It decomposes on heating to generate bubbles of carbon dioxide (leaving holes in cakes or pastries and making them light and fluffy).
• For skin infections, sodium hydrogen carbonate is a moderate antiseptic. It's a component of fire extinguishers.

A fine coating of calcium carbonate is formed on the walls as a result of a slow reaction between calcium hydroxide, Ca(OH)2, and the carbon dioxide in the air. 

Important Points:

• After two to three days of whitewashing, calcium carbonate forms and provides the surfaces a shiny sheen. 
• Slaked lime, also known as calcium hydroxide. 
• It only partially dissolves in water. 
• Lime water is a liquid solution of calcium hydroxide, and milk of lime is a mixture of slaked lime in water. 
• Calcium carbonate is formed when carbon dioxide is added to lime water, which causes the water to turn white. 
• Calcium hydrogen carbonate is created when the precipitate dissolves in extra carbon dioxide.

Methane is the first member of alkane family. Its chemical formula is CH₄.

Important Points:

• It is a saturated hydrocarbon. It is also called marsh gas.
• Methane is a greenhouse gas. It is used as a rocket fuel and as an antifreeze ingredient in industries.
• Methane gas is released from the paddy fields. It is the main constituent of natural gas. 

• Ethane – It is a saturated hydrocarbon with chemical formula C₂H₆.
• Ethene – It is an unsaturated hydrocarbon and the first member of alkene family. Its chemical formula is C₂H₄. It is also known as ethylene. It is used for the ripening of fruits.

Nitrogen is used to make ammonia by Haber’s process.

Important Points:

• Nitrogen gas is slightly lighter than air and slightly soluble in water.
• It is non -flammable and does not support combustion. 
• Nitrogen is used to make ammonia which is used for making fertilizers. 
• Nitrogen is a non-metal. 
• Nitrogen atom has two stable isotopes: ¹⁴N and ¹⁵N.

Melamine is known as fire proof plastic.

Important Points:

• Melamine plastic is known as fire proof plastic. 
• Melamine is an example of thermosetting plastic. 
• It resists fire and can tolerate heat better than other plastics. 
• It is used for making floor tiles, kitchenware and fabrics which resist fire.

Option Explanation:

Disproportionation reactions are a special type of redox reaction.

In a disproportionation reaction, an element in one oxidation state is simultaneously oxidized and reduced.

Important Points:

• Phosphorous, sulfur, and chlorine undergo disproportionation in the alkaline medium. 
• The disproportionation reaction describes the formation of household bleaching agents. 
• The hypochlorite ion (ClO^– ) formed in the reaction oxidizes the color-bearing stains of the substances to colorless compounds.

The composition of gun powder is 75% saltpeter (potassium nitrate, KNO₃), 15% Sulphur (S) and 10% charcoal.

Important Points:

• Gun powder is also known as black powder.  
• Potassium nitrate provides oxygen for the combustion reaction. 
• Sulphur lowers the ignition temperature that is required to start the reaction. It can also acts as a fuel. 
• Charcoal, a source of carbon, acts as a fuel.

White lead is the basic lead carbonate, 2PbCO₃·Pb(OH)₂.

Important Points:

• It is used as a white pigment in paints.
• It is a complex salt, containing both carbonate and hydroxide ions. 
• Lead sulfide, PbS, is known as galena. 
• Lead oxide, PbO, is known as litharge or massicot.

Potassium permanganate is known as Condy's Crystals.

Important Points:

• Potassium permanganate is a crystalline solid with a metallic sheen that dissolves readily in water.
• KMnO₄ crystals are dark purple (almost black) and isostructural with KClO₄.
• It is also known as Condy's Crystals.
• Pyrolusite ore (MnO2) is used for the production of potassium permanganate.
• It is a strong oxidizing agent.
• It is an effective disinfectant and is commonly used to treat various skin conditions, such as eczema, dermatitis, and fungal infections.
• It can also be used to purify water and as a laboratory reagent.

Option Explanation:

• Potassium aluminium sulphate is known as potash alum. Its chemical formula is K₂SO₄.Al₂(SO₄)₃.24H₂O.  
• Potassium chromium sulphate is known as chrome alum. Its chemical formula is K₂SO₄.Cr₂(SO₄)₃.24H₂O.
• The inorganic compound potassium manganate has the molecular formula K₂MnO₄.It is a green colour solid.

A-II, B-III, C-IV, D-I

Important Points:

Freon-

• The chlorofluorocarbon compounds of methane and ethane are collectively known as freons.  
• Freon 12 (CCl₂F₂ ) is used as a refrigerant. 

 Chloroform-

• The IUPAC name of Chloroform is Trichloromethane(CHCl₃). 
• It was also used as a general anaesthetic in surgery.
• Chloroform is slowly oxidised by air in the presence of light to an extremely poisonous gas, carbonyl chloride, also known as phosgene. 
• It is therefore stored in closed dark coloured bottles completely filled so that air is kept out.  

Methylene chloride-

• Dichloromethane, also known as methylene chloride is widely used as a solvent as a paint remover, as a propellant in aerosols, and as a process solvent in the manufacture of drugs.

On 2–3 December 1984, 42 tonnes of methyl isocyanate (MIC) gas leaked at the Union Carbide India pesticide plant in Bhopal.

Important point:

• Methyl isocyanate is toxic and its symptoms include cough, shortness of breath, chest pain, lacrimation, eyelid swelling, and fainting.
• It is an organic compound having the chemical formula CH3NCO.
• It is used in the production of rubber and adhesives.
• It is a colourless, poisonous, irritating gas.