CBSE Class 10 Science HOTs Carbon And its Compounds Set 02

Bonding in Carbon, Covalent Compounds, Nomenclature, Homologous Series, Properties of Compounds of Carbon

Question. —CHO represents the functional group
(a) esters
(b) carboxylic acid
(c) alcohols
(d) aldehydes
Answer: (d) aldehydes

Question. A functional group mainly determines the
(a) physical properties
(b) chemical properties
(c) both
(d) none of the options
Answer: (b) chemical properties

Question. Solubility of alcohol in water is due to
(a) low density of alcohol
(b) volatile nature of alcohol
(c) ionisation
(d) hydrogen bonding
Answer: (d) hydrogen bonding

Question. Artificial flavour for orange is obtained from
(a) amyl acetate
(b) isoamyl valerate
(c) methyl butyrate
(d) octyl acetate
Answer: (d) octyl acetate

Question. Drinking alcohol is very harmful and it ruins the health. “Drinking alcohol” stands for
(a) drinking methyl alcohol
(b) drinking ethyl alcohol
(c) drinking propyl alcohol
(d) drinking isopropyl alcohol
Answer: (b) drinking ethyl alcohol

Question. The difference in the formula and molecular masses of \( CH_3OH \) and \( C_2H_5OH \) is
(a) \( CH_3 \) and 16u
(b) \( CH_2 \) and 14u
(c) \( CH_4 \) and 18u
(d) \( CH_3 \) and 16u
Answer: (b) \( CH_2 \) and 14u

Question. Which of the following statements about graphite and diamond is true?
(a) They have the same crystal structure
(b) They have the same degree of hardness
(c) They have the same electrical conductivity
(d) They can undergo the same chemical reactions
Answer: (d) They can undergo the same chemical reactions

Question. Which of the following is ethanol?
(a) \( CH_3CHO \)
(b) \( CH_3COOH \)
(c) \( CH_3CH_2OH \)
(d) \( CH_3COOCH_3 \)
Answer: (c) \( CH_3CH_2OH \)

Question. Which of the following contains covalent bond?
(a) \( MgCl_2 \)
(b) \( CaF_2 \)
(c) \( Al_2O_3 \)
(d) \( HCl \)
Answer: (d) \( HCl \)

Question. The number of covalent bonds in \( C_4H_{10} \) is
(a) 10
(b) 8
(c) 13
(d) 12
Answer: (c) 13

Question. Which amongst the following will conduct electricity?
(a) \( C_6H_{12}O_6 \)
(b) \( KCl(s) \)
(c) \( C_2H_5OH \)
(d) \( NaCl(aq) \)
Answer: (d) \( NaCl(aq) \)

Question. The self linkage property (catenation) is maximum in
(a) carbon
(b) silicon
(c) sulphur
(d) phosphorus
Answer: (a) carbon

Question. Ethane and ethene can be distinguished by
(a) \( Br_2(l) \)
(b) \( Br_2 (aq) \) water
(c) \( Cl_2 \)
(d) \( I_2 \)
Answer: (b) \( Br_2 (aq) \) water

Question. \( CH_3CH_2OH \xrightarrow{\text{alkaline } KMnO_4} CH_3COOH, \) alkaline \( KMnO_4 \) acts as
(a) oxidising agent
(b) reducing agent
(c) dehydrating agent
(d) catalyst
Answer: (a) oxidising agent

Question. The blindness and death is caused by consuming adulterated liquor contains.
(a) \( CH_3OH \)
(b) \( CH_3COOH \)
(c) \( CH_3COCH_3 \)
(d) \( CH_3CHO \)
Answer: (a) \( CH_3OH \)

Question. Ethanol, on heating at 443 K with conc \( H_2SO_4 \) gives
(a) \( CH_2=CH_2 \)
(b) \( HC \equiv CH \)
(c) \( CH_4 \)
(d) \( C_2H_6 \)
Answer: (a) \( CH_2=CH_2 \)

Question. When sodium hydrogen carbonate is added to ethanoic acid a gas evolves. Consider the following statements about the gas evolved?
(A) It turns lime water milky.
(B) It is evolved with a brisk effervescence.
(C) It has a smell of burning sulphur.
(D) It is also by – product of respiration.
The correct statements are: [CBSE 2020]
(a) (A) and (B) only
(b) (B) and (D) only
(c) (A), (C) and (D)
(d) (A), (B) and (D)
Answer: (d) (A), (B) and (D)

Question. The IUPAC name of the following structure is
\( CH_3-CH_2-CH_2-COOH \)
(a) Pentanone
(b) Butyric acid
(c) Butanoic acid
(d) Butanone
Answer: (c) Butanoic acid

Question. On undergoing complete combustion in an adequate supply of oxygen, an organic compound produces only carbon dioxide and water vapour as the products. Based on this information, which of the following homologous series could the compound belong to?
(P) Alkanes (Q) Alcohols (R) Aldehydes
(a) only P
(b) only P or Q
(c) only Q or R
(d) any - P, Q or R
Answer: (d) any - P, Q or R

Question. A compound with which of the following functional groups is MOST LIKELY to cause the decomposition of baking soda to produce carbon dioxide?
P: —OH
Q: —CHO
R: —CO—
S: —COOH
(a) P
(b) Q
(c) R
(d) S
Answer: (d) S

Question. 1 mole of ethene and 1 mole of ethyne are separately made to completely undergo addition reaction to form the respective saturated compound. Which of the following will be DIFFERENT for the two reactions?
(P) The number of moles of the saturated compound formed.
(Q) The number of moles of the hydrogen consumed.
(a) only P
(b) only Q
(c) both P and Q
(d) neither P nor Q
Answer: (b) only Q

Question. In the compound \( CH_3-CO-CH_3 \) which of the following functional group is present?
(a) Alcohol
(b) Aldehyde
(c) Carboxylic acid
(d) Ketone
Answer: (d) Ketone

Question. Which of the following represents benzene?
(a) \( H-C \equiv C-H \)
(b) Hexane ring structure
(c) Cyclohexane ring structure
(d) \( C_6H_6 \) (hexagon with alternate double bonds)
Answer: (d) \( C_6H_6 \)

Question. There are some organic compounds in the list below:
\( C_6H_{10}, C_7H_{16}, C_8H_{16}, C_2H_2, C_5H_8 \)
Now choose the correct option: [DoE Pre-Board 2023]
(a) They are only alkenes in the list.
(b) All the compounds in the list are alkanes.
(c) There is no alkyne in the list.
(d) There are saturated and unsaturated hydrocarbons in the list.
Answer: (d) There are saturated and unsaturated hydrocarbons in the list.

Question. Which of the following compounds can be classified as unsaturated compound?
(a) Cyclopropane
(b) Ethane
(c) Ethene
(d) Ethanoic acid
Answer: (c) Ethene

Question. A student studies that vinegar, which is diluted solution of ethanoic acid freezes during winter. What does this suggest about physical properties of acetic acid?
(a) It has low boiling point.
(b) It has low melting point.
(c) It has very high boiling point.
(d) It has a very high melting point.
Answer: (b) It has low melting point.

Question. \( CHCl_3 + Cl_2 \xrightarrow{Sunlight} CCl_4 + HCl. \) How does chlorine react to hydrocarbon in presence of sunlight?
(a) It adds hydrogen into the compound.
(b) It adds an oxygen atom into the compound.
(c) It substitutes hydrogen atom from the compound.
(d) It breaks double and triple bonds into single bonds.
Answer: (c) It substitutes hydrogen atom from the compound.

Question. A student burns naphthalene. He observed it gives yellow flame with lots of smoke and sooty deposits around it. What type of hydrocarbon naphthalene contains?
(a) Unsaturated, as black smoke represents complete combustion.
(b) Unsaturated, as sooty deposit represents unburnt hydrocarbons.
(c) Saturated, as it gives yellow flame which represents complete combustion.
(d) Saturated, as burning of any substance represents complete combustion.
Answer: (b) Unsaturated, as sooty deposit represents unburnt hydrocarbons.

Question. Which of these series can be classified as homologous series?
(a) \( CHCl_3, C_2H_5OH, C_3H_7OH \)
(b) \( CH_3OH, C_2H_5OH, C_3H_7OH \)
(c) \( CHCl_3, C_4H_9OH, CH_3COOH \)
(d) \( CH_3COOH, C_4H_9OH, C_2H_5OH \)
Answer: (b) \( CH_3OH, C_2H_5OH, C_3H_7OH \)

Very Short Answer Type Questions

Question. “Carbon prefers to share its valence electrons with other atoms of carbon or with atoms of other elements rather than gaining or losing the valence electrons in order to attain noble gas configuration.” Give reasons to justify this statement.
Answer: Carbon (2, 4) has four valence electrons. It cannot lose 4 electrons because large amount of energy is needed to remove four electrons. Carbon cannot gain four electrons because 6 protons cannot hold 10 electrons. Carbon can share four electrons easily to form covalent bonds with other carbon atoms and atoms of other elements.

Question. (a) Name the following compound:
\( CH_3-CH_2-CH_2-CH_2-C \equiv CH \)
(b) Write the name and structure of an alcohol with three carbon atoms units molecule.
Answer: (a) 1-Hexyne is IUPAC name of the compound.
(b) \( CH_3CH_2CH_2OH \) or \( H-C(H_2)-C(H_2)-C(H_2)-OH \). Name: 1-Propanol.

Question. (a) How many covalent bonds are present in pentane \( C_5H_{12} \)?
(b) Write molecular formula of an alkyne containing 10 atoms of hydrogen.
Answer: (a) There are 16 covalent bonds present in \( C_5H_{12} \).
(b) \( C_6H_{10}, HC \equiv C-CH_2-CH_2-CH_2-CH_3 \)

Question. Write the next homologue of each of the following.
(a) \( C_2H_4 \) (b) \( C_4H_6 \)
Answer: (a) \( C_3H_6 \) (b) \( C_5H_8 \)

Question. Which type of hydrocarbons burn with yellow smoky flame? Why?
Answer: Unsaturated hydrocarbons. Due to presence of higher percentage of carbon.

Question. The table shows the electronic structures of four elements. Element P: 2,6 Element Q: 2,8,1 Element R: 2,8,7 Element S: 2,8,8 (a) Identify which element(s) will form covalent bonds with carbon. (b) “Carbon reacts with an element in the above table to form several compounds.” Give suitable reason.
Answer: (a) P and R
(b) Carbon has a valency four or tetravalency and catenation are responsible.

Question. “Carbon forms strong bonds with most other element making the compounds exceptionally stable”. Give reason to justify this statement.
Answer: Carbon has small atomic size and four valence electrons. It shares 4 electrons with other elements to form covalent bonds which are very strong and stable because octet of carbon become complete.

Question. Write the electron dot structure of methane (\( CH_4 \)) and ethene (\( C_2H_4 \)).
Answer:
Methane (\( CH_4 \)): Carbon atom in the center sharing its 4 electrons with 4 Hydrogen atoms.
Ethene (\( C_2H_4 \)): Two Carbon atoms sharing two pairs of electrons (double bond) between them and each sharing one pair with two Hydrogen atoms.

Question. With the help of a suitable example explain in brief the process of hydrogenation mentioning the conditions for the reaction and also state any one physical property of substances which changes due to hydrogenation.
Answer: \( C=C + H_2 \xrightarrow[heat]{Ni} CH-CH \)
When unsaturated hydrocarbons are heated with hydrogen in presence of nickel as catalyst, saturated hydrocarbons are formed. If the starting unsaturated hydrocarbons are liquids, they will change into solids. Vegetable oils are hydrogenated to form vegetable ghee by hydrogenation process.

Question. Select alkene and alkyne from the following:
\( C_6H_{12}, C_3H_4, C_2H_4, CH_4, C_4H_8, C_5H_8 \)
Answer: Alkenes: \( C_6H_{12}, C_2H_4, C_4H_8 \)
Alkynes: \( C_3H_4, C_5H_8 \)