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

Explanation:

Bakelite is a polymer that is made up of the monomers phenol and Formaldehyde. This phenol-Formaldehyde is a Thermosetting polymer.

Some important properties of Bakelite are listed below.

• It can be easily Molded.
• Very smooth molding can be obtained from this polymer.
• Bakelite moldings are heat resistant and scratch-resistant.
• Owing to its low electrical conductivity, bakelite is resistant to electric current.

Bakelite structure:

Important Points

• Bakelite is used for making electrical switches.
• Melamine is used for floor tiles.

The correct answer is High elongation.

Explanation:

Polymers

• They are giant molecules. They are important chemicals in our bodies (proteins, poly(nucleic acids)), in plants (starch, cellulose), and in our everyday lives (fibres, plastics, elastomers).
• Every polymer has its own characteristics, but most polymers have the following general properties.

Additional Information 

• Characteristics of Polymers
  • Low specific gravity and high specific strength
  • Thermal and electrical insulations
  • Corrosion and weather resistances
  • They can be processed in various ways to produce thin fibres or intricate parts (High elongation)
  • Ease in design and manufacturing of complicated structures
  • Outstanding aesthetic appeal due to ease in the adoption of permanent colours
  • Mass production with low energy-intensive manufacturing techniques
  • Ease in printability and adhesion
  • Ease in handling and cleanliness
  • Offering tremendous scope of physical and chemical modification to meet industrial and consumer requirement
  • Tremendous adaptability to low-cost production.

The correct answer is Transition elements.Key PointsSuperconductors:

• Superconductivity is a set of physical properties:
  • electrical resistance vanishes 
  • magnetic flux fields are expelled from the material.
• Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered even down to near absolute zero
• A superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero.
• An electric current through a loop of superconducting wire can persist indefinitely with no power source.
• Superconductor material classes include chemical elements (e.g. mercury or lead), alloys (such as niobium-titanium, germanium–niobium, and niobium nitride), ceramics (YBCO and magnesium diboride), etc.
• Superconductors are mostly compounds of transition metal. Hence option 4 is correct.

The correct answer is Sulphide coating on silver.

• Silver does not react with oxygen as it is highly unreactive.

Key Points

• But over time its surface turns black due to exposure to the air.
• Due to the availability of Hydrogen Sulphide (H₂S) in the air, a layer of silver Sulphide (Ag₂S) is formed and silver loses its shine.
• This blackness can be minimized by covering it with polythene.
• This blackness is a temporary effect on the surface and can be removed by rubbing with a mild soap solution prepared in warm water. 

The correct answer is Oxalic Acid.

Key Points

• Tomato is a natural source of Oxalic acid.
• Oxalic Acid is most likely to be found in Spinach.
• Oxalic acid is an organic compound found in many plants.
• Moderately high contents of oxalic acid were recorded in all varieties of tea leaves.
• Oxalic acid, also called ethanedioic acid, a colorless, crystalline, toxic organic compound belonging to the family of carboxylic acids.

Additional Information 

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 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 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 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