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

The correct answer is Quick lime.

Explanation:

• The chemical formula for quick lime calcium oxide is CaO.
• It reacts with water to form calcium hydroxide.
• The product was left immediately after the calcination of pure limestone.
• It is commonly used in making porcelain and glass and also in preparing bleaching powder
• Limestone forms from the accumulation of shell, coral, algal, and fecal debris that have calcium carbonate in them.
• The chemical composition of chalk is calcium carbonate, with minor amounts of silt and clay.
• Marble (Calcium carbonate) is a biogenic rock and is more compact than chalk.
• As with marble, calcium carbonate is a coarse-crystalline, metamorphic rock that is formed when chalk or limestone is recrystallized under conditions of high temperature and pressure.

The correct answer is H.

Key Points

• H is present in all atoms except neutrons.
  • The available hydrogen state H¹.
  • It is made of 1 electron, 1 proton, and no neutrons.
  • All other elements including isotopes of Hydrogen have neutrons.
  • Neutrons are present in the nucleus of all atoms, except hydrogen.
• All elements have atoms with neutrons except for one.
  • The normal hydrogen (H) atom does not have any neutrons in its tiny nucleus.
  • That tiny little atom (the tiniest of all) has only one electron and one proton.
  • Deuterium is a hydrogen atom with an extra neutron and tritium has two extra.

Additional Information

• Avogadro’s number is an absolute number: there are 6.023×1023 elementary entities in 1 mole.
  • This can also be written as 6.023×1023 mol-1.
• The mass of one mole of a substance is equal to that substance’s molecular weight.
  • For example, the mean molecular weight of water is 18.015 atomic mass units (amu), so one mole of water weighs 18.015 grams.
• Mole:
  • The amount of substance of a system that contains as many elementary entities as there are atoms in 12 g of carbon-12. 
  • The mole allows scientists to calculate the number of elementary entities (usually atoms or molecules ) in a certain mass of a given substance.

The correct answer is Al & P.

Key Points

• In the modern periodic table, Silicon (Z = 14) is placed between Al and P.
  • Silicon has an atomic number 14 and the outer electronic configuration is 3s² 3ps².
  • It is placed at the 3rd Period and 14th Group number.

Additional Information

• Silicon, the second most abundant element on earth, is an essential part of the mineral world.
  • Its stable tetrahedral configuration makes it incredibly versatile and is used in various ways in our everyday lives.
  • Found in everything from spaceships to synthetic body parts, silicon can be found all around us, and sometimes even in us.
  • Silicon is a crystalline semi-metal or metalloid.
  • ​It is a group 14 element in the same periodic group as carbon but chemically behaves distinctly from all of its group counterparts.
  • Silicon shares the bonding versatility of carbon, with its four valence electrons, but is otherwise a relatively inert element. 

The correct answer is Copper and Tin.

• An alloy is a homogenous mixture of metal with another metal or non-metal.
• Bronze is an alloy of copper and tin.
  • It consists of around 88% copper and 12% tin.
  • Bronze is typically used for bearings.
• Brass is an alloy of copper and zinc.
• Constantan is an alloy of copper and nickel.
• Aluminum bronze is an alloy of copper and aluminum.

• Acetic Acid is the common name of ethanoic acid.
• The chemical Formulae for Acetic Acid is CH₃COOH.
• It belongs to a group called carboxylic acid and hence they are weak acids.
• When acetic acid is diluted in water with a percentage of 5-8 then vinegar is formed.
• The melting point of acetic acid is 290k and it often freezes at room temperature, hence it has another name called Glacial Acetic Acid.

The correct answer is Sodium carbonate.

Explanation:

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

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

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.

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

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 :

">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">​​Lime water (aq) + CO2 (g)Carbon Dioxide ⟶ CaCO3 (g)Calcium Carbonate

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.

• The word ‘atom’ is coined by Democritus.
• He suggested that if we go on dividing matter at a certain point the atom becomes indivisible or cannot be divided further.
• He called these particles as atoms (Indivisible).

 

Scientist	Discovered
Thomson	Electron
E Rutherford	Discovered alpha and beta particles
John Dalton	Father of Atomic Theory

The correct answer is The acid present in tomatoes.

Key Points

• Oxalic acid is a chemical compound that occurs naturally in almost every plant to some degree, including fruit, vegetable and grain plants. 
• Tomato contains more than 10 types of acids such as citric acid, malic acid, ascorbic acid, oxalic acid etc. 
• The oxalic acid content of tomatoes is about 50 mg per 100 g serving. 

Additional Information 

• Some natural sources of acid:

The correct answer is option 1, i.e  Alkali Metals.

EXPLANATION:

• The elements in the first group of s-block are also known as Alkali Metals. These have only one electron in their outermost shell and hence are quite reactive as they easily lose their electron to form bonds with non-metals.

• The elements in the second group of s-block are also known as Alkaline Earth Metals. These have two electrons in their outermost shell and are less reactive than Alkali metals.
• Halogens are the group 17 elements and are placed in the p-block.
• Noble gases are the group 18 elements and are placed in the p-block. These are the least reactive amongst all the elements found in the periodic table as they have a stable configuration.

• 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 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