Question 1 1 / -0
Which of the following reactions yields a product used in the making of perfumes and flavouring agents?
Solution
The reaction between ethanoic acid and ethanol, in the presence of an acid, leads to the formation of ethyl ethanoate (ester), which is a sweet smelling substance used in the making of perfumes and flavouring agents.
The reaction is called esterification
.
Question 2 1 / -0
What is the solvent in vinegar?
Solution
Solute is the component of a solution, which is present in a small amount and the component of solution, which is present in a larger proportion, is the solvent. Vinegar is 5-8% solution of acetic acid and water. Therefore, acetic acid is the solute and water is the solvent in vinegar. Formic acid (HCOOH) and mineral acids (HCl, HNO3 etc) are not present in vinegar.
Question 3 1 / -0
The molecules of soaps are ________ salts of long chain ________.
Solution
The molecules of soaps are sodium or potassium salts of long chain fatty acids.
For example, C
15 H
31 COONa and C
17 H
35 COONa.
Question 4 1 / -0
When a few drops of acidified potassium dichromate are added to methanol, _______ is formed.
Solution
In the presence of strong oxidising agents (like alkaline potassium permanganate or acidified potassium dichromate), the alcohols are oxidised to form their corresponding acids. Therefore, when a few drops of acidified potassium dichromate are added to the methanol, methanoic acid (formic acid) is formed.
Question 5 1 / -0
Which of the following acids is the weakest?
Solution
Acids are those substances, which are capable of producing H+ ions in aqueous solution. Hydrochloric acid (HCl) and sulphuric acid (H2 SO4 ) are mineral acids, which get completely dissociated in water. Therefore, they are strong acids. Glacial acetic acid (CH3 COOH) does not undergo complete dissociation. So, it is a weaker acid than the others. Vinegar is 5-8% solution of acetic acid in water. So, it is the weakest acid (dilution decreases the no. of H+ ions per unit volume).
Question 6 1 / -0
Which of the following compounds cannot undergo addition reaction, but can undergo substitution reaction?
Solution
Methane is a saturated compound (suffix 'ane' indicates an alkane). So, it will undergo substitution reaction.
CH
4 + Cl
2 CH
3 Cl + HCl
But, it will not undergo the addition reaction. Unsaturated compounds are highly reactive and they undergo addition reaction to form saturated compounds. Ethene (C
2 H
4 ) is an alkene containing a double bond. Benzene (C
6 H
6 ) also contains alternate single and double bonds among carbon atoms, whereas acetylene (C
2 H
2 ) contains a triple bond. All these are unsaturated compounds and they will undergo addition reaction.
Question 7 1 / -0
Which of the following substances results from the reaction between sodium and ethanol?
Solution
Ethanol reacts with sodium metal to form sodium ethoxide. Hydrogen gas is also evolved in the reaction. The reaction takes place as follows:
In the above reaction, H
+ ion of ethanol gets exchanged with Na
+ ions to form sodium ethoxide and hydrogen.
Question 8 1 / -0
The presence of calcium and magnesium salts in water causes
Solution
The presence of calcium and magnesium salts in water causes hardness in the water. These ions form insoluble salts with soap which settle as scum.
Question 9 1 / -0
Combustion of saturated hydrocarbons produces a _______ flame and combustion of unsaturated hydrocarbons produces a _______ flame.
Solution
Combustion of saturated hydrocarbons (such as methane, ethane, propane, etc.) produces a blue flame because of its complete combustion, whereas combustion of unsaturated hydrocarbons (such as ethene, ethyne, benzene, etc.) is incomplete and it gives a yellow flame. This is because the unsaturated hydrocarbons have a greater percentage of carbon and require pure oxygen for their complete combustion. With 20% oxygen in the air, partial combustion takes place and they burn with a sooty flame.
Question 10 1 / -0
Which of the following substances is present in denatured alcohol?
Solution
Ethanol (CH3 CH2 OH) is an excellent solvent and is used in various chemical industries. To prevent its misuse for drinking purposes, the industrial alcohol is denatured, i.e. it is made unfit for drinking purposes by adding certain poisonous substances, such as methanol (CH3 OH), pyridine, CuSO4 etc. Such an alcohol is called denatured alcohol. CH3 CH2 CH2 OH is propanol and it is not present in denatured alcohol. Moreover, CH3 COOH is an ethanoic acid and not an alcohol.
Question 11 1 / -0
What product(s) is/are obtained when dichloromethane is made to react with chlorine in the presence of diffused sunlight?
Solution
Saturated hydrocarbons are quite non reactive and are inert to the action of most of the reagents. However, in the presence of heat or light, chlorine reacts very rapidly with saturated hydrocarbons to form substitution products. When dichloromethane is made to react with chlorine in the presence of sunlight, one of its hydrogen atoms gets replaced by an atom of chlorine resulting in the formation of trichloromethane and hydrochloric acid. The following reaction takes place:
In the presence of excess of chlorine, further substitution takes place and tetrachloromethane and hydrochloric acids are formed.
Question 12 1 / -0
What are the products of the reaction of ethanol with hot concentrated H2 SO4 ?
Solution
Heating ethanol at 443 K with concentrated sulhpuric acid results in the dehydration of ethanol to give ethene. The following reaction takes place:
The concentrated sulphuric acid acts as a dehydrating agent, which removes water from ethanol.
Question 13 1 / -0
Ammonium or sulphonate salts of long chain carboxylic acids are known as
Solution
Ammonium or sulphonate salts of long chain carboxylic acids are known as detergents, whereas soaps are sodium or potassium salts of long chain carboxylic acids.
Question 14 1 / -0
Which of the following subtances produces a yellow flame and soot on burning?
Solution
Saturated compounds on burning produce blue flame, but unsaturated hydrocarbons on burning produce a yellow flame with lots of black smoke and soot. This sooty deposit is actually unburnt carbon, which is produced due to incomplete combustion. The reason behind this is that carbon content of unsaturated compounds is more than the hydrogen content and hence carbon is not completely burnt and the unburnt carbon deposits as soot, Ethanol (C2 H5 OH), LPG (which is mixture of butane CH3 CH2 CH2 CH3 and propane CH3 CH2 CH3 ) and methane (CH4 ) are saturated hydrocarbons. Therefore, they burn with a blue flame whereas camphor is an unsaturated hydrocarbon. Therefore, it burns with a yellow flame and soot.
Question 15 1 / -0
What is the melting point of pure ethanoic acid?
Solution
The melting point of pure ethanoic acid is 16.6°C or 289.75 K (approx. 290 K).
Question 16 1 / -0
Reaction of chlorine with methane is a _______ reaction.
Solution
Saturated hydrocarbons are quite non reactive and are inert to the action of most of the reagents. However, in the presence of heat or light, chlorine reacts very rapidly with saturated hydrocarbons to form substitution products. For example, methane reacts with chlorine to give substitution products and rate of reaction is very fast.
Question 17 1 / -0
What are the products of the reaction of ethanoic acid with sodium hydroxide?
Solution
Ethanoic acid (acid) reacts with sodium hydroxide (base) to give sodium acetate (salt) and water (neutralisation reaction). The following reaction takes place:
Question 18 1 / -0
With which of the following types of water are soaps not effective as a cleansing agent?
Solution
Soaps are not effective in hard water because soaps react with Ca
+2 and Mg
+2 ions present in hard water resulting in the formation of insoluble precipitate called scum. For example:
Question 19 1 / -0
Which of the following equations represents the combustion of ethanol?
Solution
Ethanol burns in oxygen to form carbon dioxide and water with the release of large amount of heat and light. Therefore, the correct equation for the combustion of ethanol is:
Question 20 1 / -0
Which catalyst is used in the hydrogenation of unsaturated hydrocarbons?
Solution
Catalysts are substances which usually increase the speed of a chemical reaction without being used up in that reaction. Hydrogenation (addition of hydrogen) of unsaturated hydrocarbons takes place in the presence of nickel or palladium as the catalyst to form saturated hydrocarbons.
Question 21 1 / -0
What is the common name of ethanoic acid?
Solution
The common name of ethanoic acid (CH3 COOH) is acetic acid.
Question 22 1 / -0
Which of the following reactions represents an esterification reaction?
Solution
Reaction between a carboxylic acid and an alcohol to form an ester is called an esterification reaction. For example, when ethanoic acid reacts with ethanol in the presence of acid, ester (ethyl ethanoate) is produced. The following reaction takes place:
Thus, option (4) represents an esterification reaction.
Option (1) represents a neutralisation reaction between NaOH (base) and CH
3 COOH (acid) resulting in the formation of CH
3 COONa (salt) and water.
Reaction in option (2) represents the reaction of ethanoic acid (acid) and sodium bicarbonate (base). So, this is also not an esterification reaction.
Reaction in option (3) represents the reaction of ethanol (CH
3 CH
2 OH) with conc. H
2 SO
4 resulting in the formation of ethene (CH
2 =CH
2 ) and water. Therefore, this is also not an esterification reaction. In fact, it is a dehydration reaction.
Question 23 1 / -0
Reaction of soap with ________ results in the formation of scum.
Solution
Reaction of soap with calcium and magnesium salts (present in hard water) results in the formation of an insoluble precipitate called scum, and it is due to the formation of scum that soaps are not effective in hard water. For example,
Question 24 1 / -0
Which of the following fuels is used for welding the metals?
Solution
Ethyne (Acetylene) is used as a fuel for welding the metal as it is a carbon compound, and on combustion in air, it liberates a large amount of heat (has a high calorific value).
Question 25 1 / -0
Which of the following reactions is an example of substitution reaction?
Solution
Reaction in option (3), i.e. CH
4 + Cl
2 CH
3 Cl + HCl is a substitution reaction as in this reaction, hydrogen atom of methane, CH
4 is replaced by chlorine.
Question 26 1 / -0
What is the product of the reaction of ethanoic acid and ethanol in the presence of an acid?
Solution
Reaction between a carboxylic acid and an alcohol to form an ester is called esterification reaction. For example, when ethanoic acid reacts with ethanol in the presence of acid, ester (ethyl ethanoate) is produced. The following reaction takes place:
Ethane (C
2 H
6 ), ethene (C
2 H
4 ) and ether (compound containing –O– as functional group) are not formed as a result of the reaction between acid and alcohol.
Question 27 1 / -0
How much acetic acid is present in vinegar?
Solution
5 to 8 % solution of acetic acid in water is called vinegar and is used widely as a preservative for sausages, pickles, etc.
Question 28 1 / -0
Which of the following substances are used to make shampoos and products for cleaning clothes?
Solution
Detergents are ammonium or sulphonate salts of long chain carboxylic acid and they are used to make shampoos and products for cleaning clothes. Sodium and potassium salts of long chain carboxylic acids are called soaps and they are used for cleaning clothes, but they are not used to make shampoos. Calcium and magnesium salts of long chain carboxylic acids are insoluble. So, they cannot be used to make shampoos and products for cleaning clothes. Ammonium and cesium salts of long chain carboxylic acids are also not used to make shampoos and products for cleaning clothes.
Question 29 1 / -0
Flame is produced only when the ________ substances are burnt in a fuel.
Solution
Flame is nothing but burning vapour of the fuel. Therefore, flame is produced by the burning of gaseous fuels and by burning of fuels which vapourise on heating. For example, when wood or coal is ignited, the volatile substances (present in wood and charcoal) vapourise and burn with a flame in the beginning but when the flame subsides wood and coal being solid fuels only smoulder.
Question 30 1 / -0
The product of dehydration of ethanol is
Solution
Dehydration of ethanol in the presence of dehydrating agent (like conc. H
2 SO
4 ) results in the formation of ethene. The following reaction takes place:
Question 31 1 / -0
Reaction between _______ and _______ is called esterification reaction.
Solution
Reaction between alcohol and carboxylic acid results in the formation of esters. So, it is called an esterification reaction.
(R and R' are alkyl groups, which may be similar or different). It is not necessary that acid should be ethanoic acid and alcohol should be ethanol. It can be reaction between any carboxylic acid and any alcohol. Reaction between soap and dirt does not result in the formation of ester. Therefore, it is not an esterification reaction. Similarly, reaction between alcohol and oxygen is also not an esterification reaction.
Question 32 1 / -0
Which of the following statements is true about soap action?
Solution
Soaps are the sodium and potassium salts of long chain acids. The ionic end of soap is hydrophilic and it dissolves in water, while the carbon chain of soap is hydrophobic and it dissolves in oil.
Hence, only option (4) is correct.
Question 33 1 / -0
Combustion is a complete sequence of exothermic chemical reactions taking place between a _______ and a/an _______.
Solution
Combustion is a complete sequence of exothermic chemical reactions taking place between fuels (generally carbon or hydrocarbons) and oxidants (oxygen in the air). The products of combustion are carbon dioxide or water vapour or both depending on the fuel used.
Question 34 1 / -0
Ethanoic acid freezes in cold climates and is therefore known as
Solution
Ethanoic acid freezes in cold climates to form ice-like flakes. They look like a glacier. Therefore, ethanoic acid is also known as glacial acetic acid.
Question 35 1 / -0
What gets removed from a substance when it is dehydrated?
Solution
Dehydration refers to removal of water molecules from a substance. For example, when ethanol is treated with conc. H
2 SO
4 , it gets dehydrated (removal of water) resulting in the formation of ethene.
Removal of CO
2 from a substance is called decarboxylation.
Question 36 1 / -0
Which of the following reactions does not involve the formation of a gaseous product?
Question 37 1 / -0
What is present in the centre of a micelle?
Solution
Soaps are molecules in which the two ends have different properties. The ionic end (containing sodium or potassium ion) is soluble in water, i.e. it is hydrophilic, whereas carbon chain is soluble in oil, i.e. it is hydrophobic. Inside water, soap molecules arrange themselves in a unique orientation by forming clusters of molecules in which the carbon chains are present, and the ionic and sodium or potassium are on the surface of the cluster. This formation is called micelle. The oily dirt gets collected in the centre of the micelle.
Question 38 1 / -0
Which of the following fuels produces only CO2 , and no water vapour, on burning?
Solution
Combustion means heating of a substance strongly in the presence of air. During combustion, carbon of organic compound is oxidised to CO
2 and hydrogen to H
2 O with a release of a large amount of heat and light. Coke contains only carbon. It does not contain hydrogen. Therefore, on burning, it produces only CO
2 and no water vapour.
Ethanol (C
2 H
5 OH), acetylene (C
2 H
2 ) and methane (CH
4 ) are hydrocarbons, which contain both carbon and hydrogen. Therefore, on burning, they will give both CO
2 and water vapour.
The following reactions take place:
Question 39 1 / -0
Which of the following conditions is necessary for the chlorination of saturated hydrocarbons?
Solution
Due to the presence of strong carbon-carbon (C–C) and carbon–hydrogen (C–H) single bonds, saturated hydrocarbons are quite non-reactive and inert to action of most of the reagents. But in the presence of sunlight, chlorine reacts rapidly with saturated hydrocarbons. Chlorine can replace the hydrogen atoms of the hydrocarbon one by one. It is called substitution reaction because one type of atom or group of atoms replaces another.
For example, chlorination of methane occurs as follows:
Thus, presence of sunlight is necessary for chlorination of saturated hydrocarbons. The reaction is carried out in diffused sunlight. If carried out in direct sunlight, the reaction can be explosive.
Question 40 1 / -0
What is the most important use of vinegar?
Solution
Vinegar, which is 5-8% solution of acetic acid in water, is widely used as a preservative for sausages, pickles, etc.4 is an oxidising agent, which oxidises alcohol to carboxylic acids.
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