Draw the electron dot structure of ethyne and also draw its structural formula.
Electron dot structure of ethyne (\(C_2H_2\)):
H : C ≡ C : H
Structural formula:
H — C ≡ C — H
Write the names of the given compounds.
(a) Pentanoic acid
(b) Butyne
(c) Heptanal
(d) Pentanol
Identify and name the functional groups present in the following compounds.
(a) —OH → Hydroxyl/Alcohol
(b) —C(=O)OH → Carboxylic acid
(c) —C(=O)— → Ketone
(d) —C=C— → Alkene
A compound X is formed by the reaction of a carboxylic acid and an alcohol in the presence of a few drops of \(H_2SO_4\). The alcohol on oxidation gives the same carboxylic acid used in this reaction. Give the names and structures of the carboxylic acid, the alcohol, and the compound X. Also write the reaction.
Carboxylic acid: Ethanoic acid (\(CH_3COOH\))
Alcohol: Ethanol (\(C_2H_5OH\))
Compound X: Ethyl ethanoate (\(CH_3COOC_2H_5\))
Reaction:
\(CH_3COOH + C_2H_5OH \xrightarrow{H_2SO_4} CH_3COOC_2H_5 + H_2O\)
Why are detergents better cleansing agents than soaps?
Detergents work as cleansing agents in both soft and hard water. Their charged ends do not form insoluble precipitates with calcium and magnesium ions present in hard water.
Name the functional groups present in the following compounds.
(a) Ketone
(b) Carboxylic acid
(c) Aldehyde
(d) Alcohol
How is ethene prepared from ethanol? Give the reaction involved.
Ethene is prepared by the dehydration of ethanol using hot concentrated sulphuric acid at 443 K.
Reaction:
\(CH_3CH_2OH \xrightarrow[443K]{conc.\ H_2SO_4} CH_2 = CH_2 + H_2O\)
Intake of small quantity of methanol can be lethal. Comment.
Methanol is oxidised to methanal in the liver. Methanal reacts rapidly with cell components, causing the protoplasm to coagulate. It affects the optic nerve and may cause blindness or death.
A gas is evolved when ethanol reacts with sodium. Name the gas evolved and write the balanced chemical equation.
Gas evolved: Hydrogen
Equation:
\(2CH_3CH_2OH + 2Na → 2CH_3CH_2O^-Na^+ + H_2\)
Ethene is formed when ethanol is heated at 443 K with excess of concentrated sulphuric acid. What is the role of sulphuric acid in this reaction? Write the balanced equation.
Role: Sulphuric acid acts as a dehydrating agent.
Equation:
\(CH_3CH_2OH \xrightarrow[443K]{conc.\ H_2SO_4} CH_2 = CH_2 + H_2O\)
Write an example of a compound formed with chlorine (Group 17) and one formed with oxygen (Group 16).
(a) With chlorine: Carbon tetrachloride (\(CCl_4\))
(b) With oxygen: Carbon dioxide (\(CO_2\))
In electron dot structure, valence electrons are represented by dots or crosses.
(a) The atomic number of chlorine is 17. Write its electronic configuration.
(b) Draw the electron dot structure of a chlorine molecule.
(a) Electronic configuration: 2, 8, 7
(b) Electron dot structure: :Cl⋯Cl:
Compare the ability of catenation of carbon with silicon. Give reasons.
Carbon shows greater catenation ability than silicon because carbon–carbon bonds are stronger due to the smaller atomic size of carbon. Silicon atoms are larger, making Si–Si bonds weaker.
Unsaturated hydrocarbons contain multiple bonds and show addition reactions. Give the test to distinguish ethane from ethene.
Burning test: Unsaturated hydrocarbons (like ethene) burn with a yellow smoky flame, while saturated hydrocarbons (like ethane) burn with a clear blue flame.
Match the reactions in Column (A) with the names in Column (B).
(a) → (iv)
(b) → (i)
(c) → (ii)
(d) → (iii)
Write the structural formulae of all the isomers of hexane.
(a) n-Hexane
(b) 2-Methylpentane
(c) 3-Methylpentane
(d) 2,3-Dimethylbutane
(e) 2,2-Dimethylbutane
What is the role of the metal or reagents written on the arrows in the chemical reactions?
(a) Ni acts as a catalyst.
(b) Concentrated \(H_2SO_4\) acts as a catalyst.
(c) Alkaline \(KMnO_4\) acts as an oxidising agent.