CBSE Class 10 Science Carbon and its Compounds VBQs Set 02

ASSERTION AND REASON QUESTIONS

Direction: The questions given below consist of an assertion and the reason. Use the following key to choose the appropriate answer.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: Vegetable oils are healthier than animal fats.
Reason: Vegetable oils generally have long unsaturated carbon chains while animal fats have saturated carbon chains.
(a) A
(b) B
(c) C
(d) D
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: Ammonia is an ionic compound.
Reason: Covalent compounds are formed by sharing of electrons.
(a) A
(b) B
(c) C
(d) D
Answer: (d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: Methane is simplest saturated hydrocarbon which is a major component of natural gas.
Reason: Methane belongs to alkene.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (c) Assertion is true but the Reason is false.

Question. Assertion: Ethanol is present in alcoholic drinks.
Reason: Ethanol has formula \( CH_3OH \).
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (c) Assertion is true but the Reason is false.

Question. Assertion: Ethanoic acid reacts with ethyl alcohol in presence of conc \( H_2SO_4 \) to form ethyl ethanoate.
Reason: Esters are used in ice creams and cold drinks.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. Assertion: Vegetable oils are unsaturated, react with hydrogen in presence of nickel to form vegetable ghee.
Reason: This reaction is saponification.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (c) Assertion is true but the Reason is false.

Question. Assertion: In a homologous series of alcohols, the formula for the second member is \( C_2H_5OH \) and the third member is \( C_3H_7OH \).
Reason: The difference between the molecular masses of the two consecutive members of a homologous series is 144.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (c) Assertion is true but the Reason is false.

Question. Assertion: Soaps are 100% biodegradable but do not work well with hard water.
Reason: Some detergents are not bio-degradable but work well with hard water.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. Assertion: Esterification is a process in which a sweet smelling substance is produced.
Reason: When esters react with sodium hydroxide an alcohol and sodium salt of carboxylic acid are obtained.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. Assertion: Butane exhibits isomerism.
Reason: Butane is a saturated hydrocarbon.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. Assertion: Carbon forms strong and stable covalent bonds.
Reason: Carbon is tetravalent and the Carbon atom is small in size.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: Following are the members of a homologous series: \( CH_3OH, CH_3CH_2OH, CH_3CH_2CH_2OH \).
Reason: A series of compounds with same functional group but differing by \( -CH_2- \) in unit is called homologous series.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: Ethanoic acid is also known as glacial acetic acid.
Reason: The melting point of pure ethanoic acid is 290 K and hence it often freezes during winters in cold climates.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: Carbon has a strong tendency to either lose or gain electrons to attain noble gas configuration.
Reason: Carbon has four valence electrons in outermost shell and has the tendency to share electrons with carbon or other elements.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (d) The statement of the Assertion is false but the Reason is true.

Carbon has four valence electrons. It cannot lose or gain four electrons. It can share four electrons easily. It forms large number of covalent compounds due to property of catenation and tetra valency. Carbon has three crystalline allotropes-diamond, graphite and fullerene which differ in physical properties. Alkanes are saturated hydrocarbons, undergo combustion and substitution reactions. Alkenes and alkynes are unsaturated hydrocarbons undergo addition reactions. Ethanol on dehydration with conc. \( H_2SO_4 \) at 443K gives ethene. Hydrogenation of vegetable oils in presence of nickel forms vegetable ghee. Alcohol react with carboxylic acid in presence of conc. \( H_2SO_4 \) to form esters, pleasant fruity smelling compounds. Alcohol and carboxylic acids react with Na metal to liberate hydrogen. Acetic acid reacts with \( NaHCO_3 \) and \( Na_2CO_3 \) to give \( CO_2 \) which turns lime water milky. Esters on heating with \( NaOH \) to give sodium salt of acid and alcohol. Soaps are prepared by saponification of fat or oil with \( NaOH \). Detergents are more effective and work well with hard water but some of them are non-biodegradable.

Question. ‘X’ on combustion gives yellow sooty flame. ‘X’ is saturated or unsaturated?
Answer: ‘X’ is unsaturated because unsaturated hydrocarbons burn with a yellow sooty flame due to incomplete combustion of high carbon content.

Question. Which types of fatty acids are good for health?
Answer: Unsaturated fatty acids are generally considered good for health.

Question. Give two properties of covalent compounds.
Answer: 1. They have low melting and boiling points. 2. They are generally poor conductors of electricity.

Question. What happens when propanol reacts with sodium metal?
Answer: When propanol reacts with sodium metal, it forms sodium propoxide and hydrogen gas.
\( 2C_3H_7OH + 2Na \rightarrow 2C_3H_7ONa + H_2 \)

Alcohols form a homologous series with general formula \( C_nH_{2n+1} — OH \) and hydroxyl (—OH) group as functional group. Alcohols are colourless liquids, boiling points higher than hydrocarbons, soluble in water. Lower alcohols have specific smell and burning taste. Their boiling point increases with increase in molecular weight but solubility in water decrease. Methanol is called wood spirit used as disinfectant. Ethanol is commonly called alcohol and is used in alcoholic drinks. It is good solvent, used in medicines, cough syrups, tonics. Consumption of alcohol leads to loss of muscular and nervous control. Intake of small amount of pure alcohol can be fatal and long term consumption of alcoholic drinks cause many health problems and ruin family life. Drinking methanol may lead to blindness and even death.

Question. Write structural formula of 5th member of alcohol homologous series.
Answer: The 5th member of the alcohol homologous series is Pentanol. Its structural formula is \( CH_3—CH_2—CH_2—CH_2—CH_2—OH \) or \( C_5H_{11}OH \).

Question. What happens when 1-propanol is heated with conc \( H_2SO_4 \)? Write chemical reaction.
Answer: When 1-propanol is heated with concentrated \( H_2SO_4 \) at 443 K, it undergoes dehydration to form propene.
\( CH_3CH_2CH_2OH \xrightarrow{\text{conc. } H_2SO_4, 443 K} CH_3CH=CH_2 + H_2O \)

Question. What happens when ethanoic acid reacts with 1-propanol in presence of conc \( H_2SO_4 \)? What is name of reaction?
Answer: When ethanoic acid reacts with 1-propanol in the presence of concentrated \( H_2SO_4 \), an ester called propyl ethanoate and water are formed. This reaction is known as esterification.
\( CH_3COOH + CH_3CH_2CH_2OH \xrightarrow{\text{conc. } H_2SO_4} CH_3COOCH_2CH_2CH_3 + H_2O \)

Question. What happens when ethyl ethanoate reacts with \( NaOH \)? What is name of the reaction?
Answer: When ethyl ethanoate reacts with sodium hydroxide (\( NaOH \)), it breaks down into sodium ethanoate and ethanol. This reaction is known as saponification.
\( CH_3COOC_2H_5 + NaOH \rightarrow CH_3COONa + C_2H_5OH \)

Hydrocarbons are the organic compounds of carbon and hydrogen, which are obtained from coal, petroleum and natural gas. Hydrocarbons and their derivatives may be saturated, unsaturated, cyclic and aromatic. Due to their large number, in order to correlate and have a systematic study of organic compounds they have been further classified into a number of series or families known as homologous series.

Question. Out of ethane, ethanol and ethanoic acid, which has lowest boiling point?
Answer: Out of ethane, ethanol, and ethanoic acid, ethane has the lowest boiling point because it is a non-polar hydrocarbon with weak Van der Waals forces, whereas ethanol and ethanoic acid exhibit strong hydrogen bonding.

Question. What is formula for cyclohexane?
Answer: The formula for cyclohexane is \( C_6H_{12} \).

Question. What is general formula of ketone? Write formula of ketone with four carbon atoms.
Answer: The general formula of ketone is \( C_nH_{2n}O \) or \( R—CO—R' \). The formula of a ketone with four carbon atoms (butanone) is \( CH_3—CO—CH_2—CH_3 \) or \( C_4H_8O \).

Question. What is general formula of alkyl group? Give formula for n-pentyl group.
Answer: The general formula of an alkyl group is \( C_nH_{2n+1} \). The formula for the n-pentyl group is \( —C_5H_{11} \).

Observe the table of boiling points of alcohols and carboxylic acids. Study this table and answer the questions related to studied concepts.
1. Methanol (64°C), 2. Ethanol (78°C), 3. Propanol (97°C), 4. Butanol (117°C), 5. Methanoic acid (101°C), 6. Ethanoic acid (118°C), 7. Propanoic acid (141°C), 8. Butanoic acid (164°C).

Question. Why do acids have higher boiling points than alcohol?
Answer: Carboxylic acids have higher boiling points than alcohols of comparable molecular mass because they form more extensive and stronger intermolecular hydrogen bonds, often existing as stable dimers.

Question. Why does ethanol have higher boiling point than \( CH_3OH \)?
Answer: Ethanol has a higher boiling point than methanol because it has a higher molecular mass and larger surface area, leading to stronger Van der Waals forces of attraction between molecules.

Question. (i) What is vinegar? (ii) What is glacial acetic acid?
Answer: (i) Vinegar is a 5-8% solution of ethanoic acid in water.
(ii) Glacial acetic acid is 100% pure ethanoic acid. It is called "glacial" because its melting point is 290 K, causing it to freeze into ice-like crystals in cold climates.

Question. (i) Which acid is present in Rancid butter? (ii) What happens when 5% alkaline \( KMnO_4 \) is added to butanol?
Answer: (i) Butyric acid (Butanoic acid) is present in rancid butter.
(ii) When 5% alkaline \( KMnO_4 \) is added to butanol, it oxidizes the butanol to form butanoic acid.

Soaps and detergents are cleansing agents. Soaps are sodium or potassium salts of higher fatty acids. Detergents are sodium or potassium salts of sulphonic acids. Soaps do not work well with hard water whereas detergents work well with hard water. Soaps are biodegradable and do not create water pollution. Some detergents create water pollution.

Question. Write functional group present in detergent.
Answer: The functional group present in detergents is the sulphonate group (\( —SO_3Na \)) or the sulphate group (\( —SO_4Na \)).

Question. Name the useful product obtained in saponification of oil or fat to form soap.
Answer: Glycerol (Glycerine) is the useful byproduct obtained during the saponification process.

Question. Give two examples of soaps.
Answer: Examples of soaps include Sodium Stearate and Sodium Palmitate.

Question. Give two examples of detergents.
Answer: Examples of detergents include Sodium n-dodecyl benzene sulphonate and Sodium n-dodecyl sulphate.

The element carbon occurs in different forms in nature with widely varying physical properties. Both diamond and graphite are formed by carbon atoms, the difference lies in the manner in which the carbon atoms are bonded to one another. Diamond is hard whereas graphite is soft and slippery. Graphite is conductor of electricity whereas diamond is not conductor. Fullerenes form another class of carbon in which carbon atoms (C-60) arranged in shape of football.

Question. What is name given to forms of same element which differ in physical properties? Which form of carbon is purest?
Answer: Different forms of the same element that differ in physical properties are called allotropes. Fullerenes (like C-60) are considered the purest form of carbon because they have a well-defined molecular structure without surface dangling bonds.

Question. Why is diamond hard?
Answer: Diamond is hard because each carbon atom is covalently bonded to four other carbon atoms in a rigid, three-dimensional tetrahedral structure, creating a very strong and stable network.

Question. How are diamonds synthesised? Why do they not conduct electricity?
Answer: Synthetic diamonds are made by subjecting pure carbon to extremely high pressure and temperature. Diamonds do not conduct electricity because all four valence electrons of each carbon atom are used in forming covalent bonds, leaving no free electrons to conduct charge.

Question. Why is graphite soft and slippery and how valency of carbon satisfied?
Answer: Graphite is soft and slippery because it consists of layers of carbon atoms arranged in hexagons; these layers are held together by weak Van der Waals forces, allowing them to slide over each other. In graphite, each carbon atom is bonded to three others, and the fourth valence electron is delocalized between the layers, satisfying the valency.

Covalent bonds are formed by sharing electrons. Not just carbon, but many other elements form molecules by sharing electrons in this manner. The shared electrons belong to outer shells of both the atoms and lead to both atoms attaining the noble gas configuration. Hydrogen is simplest molecule formed in this manner. Single bond is formed between two hydrogen atoms by sharing one electron each. Double bond is formed by sharing two electrons each. Triple bond is formed by sharing three electrons each. Ammonia, water, methane also have covalent bonds. Covalently bonded molecules are seen to have strong bonds within the molecule but intermolecular forces are small.

Question. Hydrogen molecule acquires stable electronic configuration of which noble gas after forming covalent bonds?
Answer: After forming covalent bonds, a hydrogen molecule acquires the stable electronic configuration of Helium (\( He \)).

Question. Draw the electron dot diagram of nitrogen.
Answer: Nitrogen (\( N_2 \)) has 5 valence electrons. Two nitrogen atoms share three pairs of electrons to form a triple bond: \( :N \equiv N: \).

Question. Draw the electron dot diagram of ammonia. Does it conduct electricity? Give reason.
Answer: In ammonia (\( NH_3 \)), the central nitrogen atom shares three electrons with three hydrogen atoms. It does not conduct electricity because it is a covalent compound and does not have free ions or electrons to carry current.

Question. Draw electron dot diagram of water molecule. Which has higher boiling point-\( H_2O \) or \( NaCl \)? Give reason.
Answer: In water (\( H_2O \)), oxygen shares one electron with each of two hydrogen atoms. \( NaCl \) has a higher boiling point than \( H_2O \) because \( NaCl \) is an ionic compound with strong electrostatic forces between ions, whereas \( H_2O \) is a covalent molecule with weaker intermolecular forces (hydrogen bonding).

Have you ever observed either a coal or a wood fire? If not, the next time you get a chance, take a note of what happens when wood or coal starts to burn. You must have seen above the candle or the LPG in gas stove burns with a flame. However, you will observe that coal or charcoal in an ‘angithi’ sometimes just glows red and gives out heat without a flame. There are two types of flames, luminous flame and non luminous flame. The colour produced by each element is characteristic property of that element. Try and heat a copper wire in flame of a gas stove and observe its colour. Some compounds, on combustion give sooty (smoky) flame. Heat common salt in flame and observe the colour of the flame. Coal and petroleum are fossil fuels and create lot of pollution on combustion. Ethanol burns with blue flame and creates less pollution. Hydrogen is best fuel.

Question. Why do some substances on combustion produce flame, others do not?
Answer: A flame is produced only when the combustible substances vaporize during burning. For example, wax and LPG vaporize and produce a flame, whereas coal or charcoal do not vaporize and only glow red.

Question. What type of hydrocarbons burn with blue (non-luminous) flame and why?
Answer: Saturated hydrocarbons (like methane or LPG) generally burn with a clean blue flame because they have a low carbon content and undergo complete combustion in the presence of sufficient oxygen.

Question. Among LPG, ethanol, hydrogen, coal arrange them in increasing order of suitability in order to reduce pollution? Give reason.
Answer: The increasing order of suitability to reduce pollution is: Coal < LPG < Ethanol < Hydrogen.
Reason: Coal produces the most pollution due to impurities and incomplete combustion. LPG and Ethanol are cleaner fuels, and Hydrogen is the best fuel as its combustion product is only water vapor.

Question. Which coloured flame is produced by (i) Heating copper wire in flame (ii) Sodium chloride in flame? Why do elements produce specific colour flame?
Answer: (i) Copper wire produces a blue-green/green flame.
(ii) Sodium chloride produces a golden yellow flame.
Elements produce specific colored flames because their electrons jump to higher energy levels when heated and release energy of a characteristic wavelength (color) when they return to their ground state.