Chemistry MCQ Quiz - Objective Question with Answer for Chemistry - Download Free PDF

The correct answer is More than one of the above.

Key Points

Concept:

• Corrosion: The eating away of the surface of metals due to the action of air, moisture, or chemicals is called corrosion. 

Explanation:

The rusting of iron can be prevented by painting, oiling, greasing, galvanizing, chrome plating, anodizing, or making alloys.

• Galvanization: It is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc.
• Alloying: An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. When iron is mixed with nickel and chromium, we get
  stainless steel, which is hard and does not rust.
• Anodising: It is an electrolytic process in which a layer of oxide is formed on the metal surface making it resistant to further corrosion.
• Painting, oiling, and greasing form a protective film between air and the surface of iron protecting it from corrosion. 

Additional InformationSoldering:

• It is a joining process used to join different types of metals together by melting solder.
• Solder is an alloy usually made of tin and lead.

Thermit reaction: 

• The displacement reaction between iron oxide and aluminum releasing a lot of heat is called the thermit reaction.
• It is used to join railway tracks or cracked machine parts. 

Carbonization: 

• The dead plants and vegetation due to temperature and high pressure over hundreds of years slowly turned into coal.
• This slow conversion of dead plants and forests into coal is called the process of carbonization.

The correct answer is Iodine.

Key Points

• Iodine is a chemical element. The body needs iodine but cannot make it.
• The iodine needed by the body must come from the diet. As a rule, there is very little iodine in food, unless it has been added during processing.
• Processed food typically contains more iodine due to the addition of iodized salt.
• Symbol: I
• Atomic mass: 126.90447 u
• Atomic number: 53
• Electron configuration: [Kr] 4d105s25p5
• Electronegativity: 2.66
• Van der Waals radius: 198 pm
• Uses of iodine:
  • ​Promoting thyroid health.
  • Reducing risk for some goiters.
  • Managing overactive thyroid gland.
  • Treating thyroid cancer.
  • Neurodevelopment during pregnancy.

Additional Information

• Silicon:

• Germanium:

• Carbon:

The correct answer is John Dalton.

Key Points

• This law of multiple proportions is also known as Dalton's law because this law was announced (1803) by the English chemist John Dalton.
• Law of multiple proportions:
  • if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element, are in the ratio of small whole numbers.
  • Hydrogen combines with oxygen to form two compounds, water and hydrogen peroxide.
    Hydrogen + Oxygen → Water
          2g             16g          18g
    Hydrogen + Oxygen → Hydrogen Peroxide
          2g             32g          34g
  • Masses of oxygen is16 g (in water) and 32 g (in hydrogen peroxide) combine with 2g of hydrogen, bear a simple ratio, 16:32 or 1: 2.

Additional Information

• Avogadro's Law: Equal volumes of all gases at the same temperature and pressure should contain the equal number of molecules. 
• Gay Lussac's law of gaseous volume: The gases combine in a simple ratio by volume, when they are kept at constant temperature and pressure.

The correct answer is Oxygen.

Key Points

• Antoine-Laurent de Lavoisier is considered the “father of modern chemistry”.
• He was the first to establish that sulphur as an element, not a compound.
• In 1778, he named oxygen and in 1783 he named hydrogen.
• He discovered the law of conservation of mass. i.e The law of conservation of mass states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations.

Additional Information

The correct answer is Plaster of Paris.

Key Points

• Glass is formed when molten material is cooled so quickly that its constituent atoms do not have time to align themselves into an ordered lattice. 
• Soda ash varies in density, size, and shape when mined and processed. 
  • This flexibility allows it to be used in a variety of everyday products like glass. 
  • Specifically, soda ash is used to make the most common type of glass, soda-lime silica glass.
  • It is used as the main ingredient because soda ash naturally reduces melting temperatures and its alkali effectively supports the shaping of the glass item. 
• Alumina is used in glassmaking because of its superior mechanical and optical properties. 
  • Alumina can form glass if it is alloyed with calcium or rare-earth oxides.
  • But the required quenching rate can be as high as 1000 degrees per second, which makes it difficult to produce bulk quantities.
• Glass manufacturers add borax to the silica base to:
  • significantly lower melting temperature and viscosity, inhibit crystallization of the glass, control thermal expansion, and inhibit devitrification.
    • The resulting products have inherent durability and chemical resistance and are tough enough to withstand considerable mechanical or thermal shock.

K2CO3 or potassium carbonate is known as pearl ash.

• Pearl ash, in ancient times, was created by baking potash in a kiln in order to remove impurities. The remaining fine, white powder was pearl ash.
• Potassium carbonate is an inorganic compound and a white salt which is soluble in water.
• It is mainly used in the production of glass and soap.

Additional Information

 Key Points

• Atomic Mass of the Hydrogen = 1
• Atomic Mass of the oxygen = 16

Explanation:

1 mole of hydrogen = 1gm

1 mole of oxygen = 16gm

Water (H2O) = 2 Hydrogen atoms + 1 Oxygen atom

2 mole of hydrogen = 2gm

1 mole of oxygen = 16 gm

The ratio of the mass of Hydrogen: Ratio of mass of Oxygen =  2/16 = 1/8 

The ratio of the mass of Hydrogen to the mass of Oxygen in water is always 1:8.

• The number of water molecules present is washing soda is 10.
• We know the molecular formula for Washing Soda is Na₂CO₃.10H₂O.
• Recrystallisation of Sodium Carbonate (Na₂CO₃) gives washing soda.
• In a Washing soda, water is present in the form of crystals.

The correct answer is Vermilion.

• Mercury Sulfide is also known as Vermilion.
• It is a chemical compound composed of the chemical elements mercury and sulfur.
• The chemical formula of Mercury sulfide is HgS.
• It is dimorphic with two crystal forms:
  • Red cinnabar
  • Black metacinnabar

Additional Information

• Marsh Gas is the common name of Methane with the formula of CH₄.
• Mohr's Salt is the common name of Ammonium Ferrous Sulphate with the formula of (NH₄)2Fe(SO₄)₂(H₂O)₆.
• Potash Alum is the common name of Potassium Aluminium Sulphate with the formula of KAl(SO₄)₂.

Explanation:

• Calcium hydroxide is sparingly soluble in water producing an alkaline solution known as limewater.
• Calcium Carbonate is a chemical compound found commonly in rocks as minerals and is the main component of pearls and the shells of marine organisms, eggs, etc.
• When carbon dioxide gas is passed through or over limewater, it turns milky due to the formation of calcium carbonate.
• In the chemical reaction it can be shown as :

\(\rm \underset{Lime\ water}{Ca (OH)_2} \ (aq) \ + \ \underset{Carbon \ Dioxide}{CO_2 \ (g) }\ \longrightarrow \ \underset{Calcium \ Carbonate}{CaCO_3 \ (g)}\)Ca(OH)2Lime water (aq) + CO2 (g)Carbon Dioxide ⟶ CaCO3 (g)Calcium Carbonate" id="MathJax-Element-1-Frame" role="presentation" style="display: inline; position: relative;" tabindex="0">Ca(OH)2Lime water (aq) + CO2 (g)Carbon Dioxide ⟶ CaCO3 (g)Calcium Carbonate" role="presentation" style="display: inline; position: relative;" tabindex="0">Ca(OH)2

• However, when an excess of CO2 ​is passed through this solution, the milkiness disappears. This is due to the formation of calcium bicarbonate which is colorless and soluble in water.

Ca(OH)2Lime water (aq) + CO2 (g)Carbon Dioxide ⟶ CaCO3 (g)Calcium Carbonate" role="presentation" style="display: inline; position: relative;" tabindex="0">​\(\rm \underset{Lime\ water}{Ca (OH)_2} \ (aq) \ + \ \underset{Carbon \ Dioxide}{CO_2 \ (g) }\ \longrightarrow \ \underset{Calcium \ Carbonate}{CaCO_3 \ (g)}\)​\(\rm \underset{Lime\ water}{Ca CO_3} \ (aq) \ + \ \underset{Carbon \ Dioxide}{CO_2 \ (g) }\ \longrightarrow \ \underset{Calcium \ Carbonate}{Ca(HCO_3)_2 \ (g)}\)Lime water (aq) + CO2 (g)Carbon Dioxide ⟶ CaCO3 (g)Calcium Carbonate\(\rm \underset{Calcium\ Carbonate}{Ca CO_3} \ \ +H_2O+ \ \underset{Carbon \ Dioxide}{CO_2 \ (g) } \ \longrightarrow \ \underset{Calcium \ bi\ Carbonate}{Ca(HCO_3)_2 \ (g)}\)

Additional Information Reaction involved-

CaCO₃ + 2HCl →  CaCl₂ + CO₂ + H₂O

• The evolved gas is carbon dioxide which then passes through lime water and turns it milky.

Ca(OH)₂ + CO₂ → H₂O + CaCO₃  

• Due to formation of these compounds
• when excess CO₂ is passed

CaCO₃ + H₂O + CO₂ →  Ca(HCO₃)₂ 

• Bicarbonate is formed which again clears the solution

Mistake Points

•  Do not confuse Calcium carbonate and calcium bicarbonate.
• One produces white colour while the other makes it colourless.

• Aluminium (Al) metal reacts with steam to form a metal oxide and hydrogen.
• This reaction can be given as

2Al + 3H₂O (g) → Al₂O₃ + 3H₂ (g)

• Other metals of this type are Iron (Fe) and Zinc (Zn).

• But these metals do not react with either hot or cold water.

The correct answer is Lactic Acid.

Key Points

• Lactic acid is present in Sour milk or curd.
• The sourness of the milk is due to the presence of lactic acid.
• Human beings feel tired due to the accumulation of lactic acid in the muscles.​

Additional Information

The correct answer is Sodium carbonate.

• Washing soda is a chemical compound with the formula Na₂CO₃, known as sodium carbonate, and it's a salt of carbonic acid.

Key Points

• Properties of a Washing soda:
  • It is a transparent crystalline solid.
  • It is one of the few metal carbonates which are soluble in water.
  • It is alkaline with a pH level of 11, it turns red litmus to blue.
  • It has detergent properties or cleansing properties because it can remove dirt and grease from dirty clothes, etc.
  • It attacks dirt and grease to form water-soluble products, which are then washed away on rinsing with water. 

Important Points

Some common chemical compounds with their common names are:

pH of some common aqueous solutions

The correct answer is increases.

Important Points

• In normal cases, the volume of substances increases on heating and decreases while cooling.
• When 1 litre of water is cooled from 4°C to 0°C volume of water will start increasing this due to water's unique property known as 'Anomalous Expansion of Water'.
• Anomalous Expansion of Water occurs between 4°C to 0°C.
• The density of water is a maximum at 4 °C.
• When water is cooled from 4°C to 0°C, its density decreases.
• The anomalous expansion of water helps preserve aquatic life during very cold weather.

Explanation:

• When water reaches 4°C the molecules have been pushed as close to one another as possible and the density of water becomes precisely 1.00 g/cm³
• When water freezes at 0°C due to the crystal structure the molecules arranged in some structured fashion so a little far apart ended up less dense - 0.93 g/cm³  - and so floats due to buoyancy.

As density decreases the volume increases.

Volume = mass /density.

Key Points

• The elements in 18 group of the periodic table have a complete Outer Shell.
• In the 18^th group of the modern periodic table, the noble gases placed.

There are 7 noble gases in the periodic table.

They are Helium (He) with atomic number 2,

• Neon (Ne) with atomic number 10,
• Argon (Ar) with atomic number 18,
• Krypton (Kr) with atomic number,
• Xenon (Xe) with atomic number 54,
• Radon (Rn) with atomic number 86,
• Ununoctium (Sun)/Oganesson (Og) with atomic number 118.

The correct answer is Zn.

Key Points

• Only a few elements have been found to be absolutely essential for plant growth and metabolism.
• These elements are further divided into two broad categories based on their quantitative requirements: (i) Macronutrients, and (ii) Micronutrients.
• Macronutrients are generally present in plant tissues in large amounts.
  • The macronutrients include carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorous (P), sulphur (S), potassium (K), calcium (Ca) and magnesium (Mg).
  • Of these, carbon, hydrogen and oxygen are mainly obtained from CO₂ and H₂O, while the others are absorbed from the soil as mineral nutrition.
• Micronutrients or trace elements are needed in very small amounts.
  • These include iron, manganese (Mn), copper (Cu), molybdenum (Mo), zinc (Zn), boron (B), chlorine (Cl) and nickel (Ni).

Additional Information

• In addition to the 17 essential elements named above, there are some beneficial elements such as sodium (Na), silicon (Si), cobalt (Co) and selenium (Se). They are required by higher plants

The correct answer is Double displacement reaction.

Concept:

Chemical reaction:

• It is a process in which one or more substances, the reactants, are converted to one or more different substances, the products.
• A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products.

Explanation:

• Double displacement reaction: 

• It is a chemical reaction in which two compounds react and exchange their ions forming new products. 
• This reaction often results in the formation of an insoluble compound called a precipitate. 
• Such reactions are represented by equations of the following form: A⁺B^- + C⁺D^- → A⁺D^- + B^-C⁺

​In the given chemical reaction: 

NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(s)

The reactants NaCl and AgNO₃ have exchanged their ions to form NaNO3  and AgCl. 

Thus, it is an example of a double displacement reaction.^​

^{Additional Information}

Types of Chemical Reactions:

Combination reaction:

• Two or more elements or compounds combine together to form a single compound.
• Such reactions are represented by equations of the following form:     A + B → AB.

Decomposition reaction:

• The opposite of a combination reaction, a complex molecule breaks down to make simpler ones.
• Such reactions are represented by equations of the following form: AB → A + B.

Displacement reaction:

• One element takes place with another element in the compound.
• Such reactions are represented by equations of the following form: A + BC → AC + B.

Redox reaction:

• It is a reaction in which one species is reduced and the other is oxidized. 
• Reduction means losing Oxygen or gaining hydrogen 
• Oxidation means gaining oxygen or losing hydrogen. 

The Correct Answer is Option (4) i.e. Potassium.

• Potassium belongs to the group of alkali metals and belongs to the group-1 of the periodic table which lies in the s-block of the periodic table.
• The alkali metals consist of the chemical elements lithium, sodium, potassium, rubidium, cesium, and francium.
• The alkaline earth metals are six chemical elements in group-2 of the periodic table.
• Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium are the six elements of the group of alkaline earth metals.

The correct answer is Both of them undergo sublimation.

Important Points

• Both camphor and ammonium chloride are solid at room temperature.
• But they are vaporised (gas phase) when heat is applied.
  • This property is called Sublimation.

Key Points

• Sublimation - Direct conversion of a solid into the vapour state is called sublimation.
• The heat of sublimation - Heat required to change a unit mass of solid directly into vapour, at a given temperature, is called the heat of sublimation at that temperature.

Additional Information

• Camphor:
  • Colourless or white crystalline powder, flammable, waxy with a strong mothball-like odour.
  • Molecular Formula: C₁₀H₁₆O.
  • Organic compound.
• Ammonium chloride:
  • Molecular Formula: NH₄CL
  • Also, called sal ammoniac (White crystalline salt).
  • Inorganic compounds and highly soluble in water, alcohol, methanol, glycerol, etc.
  • Ammonium Chloride gives an acidic solution by dissolving in water.
  • Inorganic compound.

The correct answer is Methanoic acid.

Key Points

• Nettle is an herbaceous plant that grows in the wild.
• Nettle leaves have stinging hair, which causes painful stings when touched accidentally. 
• This is due to the methanoic acid secreted by them. 
• A traditional remedy is rubbing the area with the leaf of the dock plant, which often grows beside the nettle.

Additional Information

The correct answer is CaSO4.1/2 H2O.

​EXPLANATION:

• Plaster of Paris (POP) is a quick-setting gypsum plaster consisting of a fine white powder (calcium sulfate hemihydrate), which hardens when moistened and allowed to dry.
• It is also known as the Plaster of Paris because for the preparation of POP, the abundant gypsum was first found near the capital city of France i.e. Paris.
• The chemical formula of the Plaster of Paris is CaSO4.\(\frac{1}{2}\) H2O. Therefore option 3 is correct.
• Application of Plaster of Paris is as follows
  1. It is used as a building material as a protective coating on walls and ceilings.
  2. It is used as a moulding and vesting agent for decorative elements.
  3. It is also used for aesthetic touch to the construction elements.
  4. It is also used as plaster in orthopaedics and as a filling material by dentists, etc.

Mistake Points

• Gypsum is an ore of Calcium (Ca). The chemical formula of Gypsum is CaSO4. 2H2O.
• Gypsum is mainly used as a fertilizer, as the main constituent in plaster, chalk, etc.
• The plaster of Paris on mixing with water produces gypsum.
• Calcium Sulphate Hemihydrate (CaSO4·1/2 H2O) on hydration leads to the crystallization of gypsum calcium sulphate dihydrate (CaSO4·2H2O).

The correct answer is 17th.

• The Halogens are the elements belonging to Group 17 in the periodic table.

• A periodic table is an arrangement of elements based on their atomic numbers and chemical properties.
• It is divided into 18 groups and 7 periods running vertically and horizontally respectively.
• The periodic table accommodates a discrete combination of metal, non-metals, and metalloids.
• The elements in the periodic table are arranged horizontally in ascending order of their atomic numbers known as periods.
• Vertically the elements having identical chemical properties are clubbed together known as groups.
• The 18 groups are also known as columns and the 7 periods are also known as the rows.

Explanation:

Periods:

• Elements are arranged in increasing the atomic number of elements in a period.
• One extra electron gets added to the outermost shell as we move along the periods from left to right.
• The electron gets added to the same shell or orbit and thus the electrons present for bonding increase by one unit.
• Thus, the shell number remains the same but the number of electrons present for bonding increases along a period.

Groups:

• Elements having the same number of outer electrons are put in the same group of the periodic table.
• When we move down a group, one extra shell gets added to the elements.
• The outermost shell has electrons present for bonding.
• Though the number of shells increases as we go down in a group, the number of electrons in the outermost shell remains the same.
• For example, the Halogens F, Cl, Br, I, At all belong to group 17 and have 7 electrons in the outermost shell.
• Similarly, Group 16 elements have 6 electrons in the outermost shell, group 15 has 5 electrons in the outermost shell, and so on.

Hence, group 17 is called halogens.

Explanation:

• Sodium hydroxide (NaOH) is known as ‘Caustic Soda’.
• Some common chemical compounds with their common names are:

• The number of water molecules that combine chemically in definite molecular proportion, with the concerned salt in the crystalline state is known as the water of crystallization.
• Baking soda does NOT possess water of crystallization while other three do so.