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ScienceClass 10CBSE

1. The name of the compound CH3 — CH2 — CHO is (a) Propanal (b) Propanone (c) Ethanol Ethanal

Soln: Answer is (a) Propanal Explanation: This compound has 3 carbon atoms and an aldehyde which add suffix al to 3 carbon compound.

ScienceClass 10CBSE

1. Which of the following does not belong to the same homologous series? (a) CH4 (b) C2 H6 (c) C3 H8 (d) C4 H8

Soln: Answer is (d) C4 H8 Explanation General formula for C4H8 is CnH2n and for other option it is CnH2n+2

ScienceClass 10CBSE

1. Carbon forms four covalent bonds by sharing its four valence electrons with four univalent atoms, e.g. hydrogen. After the formation of four bonds, carbon attains the electronic configuration of (a) helium (b) neon (c) argon krypton

Soln: Answer is (b) neon Explanation: After sharing four valence electrons with univalent atoms. Electronic configuration of Carbon becomes 2.8 which is same as electronic configuration of Neon.

ScienceClass 10CBSE

1. Mineral acids are stronger acids than carboxylic acids because (i) mineral acids are completely ionised (ii) carboxylic acids are completely ionised (iii) mineral acids are partially ionised (iv) carboxylic acids are partially ionised (a) (i) and (iv) (b) (ii) and (iii) (c) (i) and (ii) (iii) and (iv)

Soln: Answer is (a) (i) and (iv) Explanation: Mineral acids are completely ionized whereas carboxylic acids are partially ionized. Hence mineral acids are stronger than carboxylic acids.

ScienceClass 10CBSE

1. Pentane has the molecular formula C5 H12. It has (a) 5 covalent bonds (b) 12 covalent bonds (c) 16 covalent bonds 17 covalent bonds

Soln: Answer is (c) 16 covalent bonds

ScienceClass 10CBSE

1. In the soap micelles (a) the ionic end of soap is on the surface of the cluster while the carbon chain is in the interior of the cluster. (b) ionic end of soap is in the interior of the cluster and the carbon chain is out of the cluster. (c) both ionic end and carbon chain are in the interior of the cluster both ionic end and carbon chain are on the exterior of the cluster

Answer is (a) the ionic end of soap is on the surface of the cluster while the carbon chain is in the interior of the cluster. Explanation: A micelle is a spherical aggregate soap molecules in soap solution. In the soap micelles the ionic end of soap is on the surface of the cluster while the carbon chain is in the interior of the cluster.

ScienceClass 10CBSE

1. Chlorine reacts with saturated hydrocarbons at room temperature in the (a) absence of sunlight (b) presence of sunlight (c) presence of water presence of hydrochloric acid

Answer is (b) presence of sunlight Explanation: In presence of sunlight Chlorine reacts with Hydrocarbons and displaces Hydrogen atoms.

ScienceClass 10CBSE

1. Identify the unsaturated compounds from the following (i) Propane (ii) Propene (iii) Propyne (iv) Chloropropane (a) (i) and (ii) (b) (ii) and (iv) (c) (iii) and (iv) (ii) and (iii)

Soln: Answer is (d) (ii) and (iii) Explanation: Propene has double bond and Propyne is having triple bond. Hence they are unsaturated compounds.

ScienceClass 10CBSE

(a) hydrophilic head and a hydrophobic tail (b) hydrophobic head and a hydrophilic tail (c) hydrophobic head and a hydrophobic tail hydrophilic head and a hydrophilic tail

Answer is (a) hydrophilic head and a hydrophobic tail Explanation: Because of hydrophobic tail Oil and grease is trapped inside a micelle. Hydrophobic head makes the outer surface of micelle. Hence micelle is easily washed by water.

ScienceClass 10CBSE

1. In which of the following compounds, — OH is the functional group? (a) Butanone (b) Butanol (c) Butanoic acid Butanal

Soln: Answer is (b) Butanol Explanation: Compound with OH Functional group will have a suffix ol in them hence answer is (b) Butanol. The soap molecule has a

ScienceClass 10CBSE

1. Oils on treating with hydrogen in the presence of palladium or nickel catalyst form fats. This is an example of (a) Addition reaction (b) Substitution reaction (c) Displacement reaction Oxidation reaction

Answer is (a) Addition reaction Explanation: Here Hydrogen is added to oil, hence it is an addition reaction.

ScienceClass 10CBSE

1. CH3 – CH2 – OH Alkaline KMnO Heat 4 + → CH3 – COOH In the above given reaction, alkaline KMnO4 acts as (a) reducing agent (b) oxidising agent (c) catalyst (d) dehydrating agent

Soln: Answer is (b) oxidising agent Explanation: Two Hydrogen atoms are replaced by an atom of oxygen making oxidation of ethanol. Here addition of oxygen is provided by potassium.

ScienceClass 10CBSE

1. Buckminsterfullerene is an allotropic form of (a) phosphorus (b) sulphur (c) carbon tin

Answer is (c) carbon Explanation: Diamond, Graphite, Lonsdaleite, C60 (Buckminsterfullerene or buckyball), C540, C70, Amorphouscarbon, and h) single-walled carbon nanotube, or buckytube. Are the allotropes of Carbon.

ScienceClass 10CBSE

1. A molecule of ammonia (NH3 ) has (a) only single bonds (b) only double bonds (c) only triple bonds two double bonds and one single bond

Answer is (a) only single bonds Explanation: Nitrogen has three electron in its outermost shell and hydrogen has 1. 3 hydrogen atoms combine with 1 nitrogen atom to make ammonia. These bonds are single bonds.

ScienceClass 10CBSE

1. Which of the following statements are usually correct for carbon compounds? These (i) are good conductors of electricity (ii) are poor conductors of electricity (iii) have strong forces of attraction between their molecules (iv) do not have strong forces of attraction between their molecules (a) (i) and (iii) (b) (ii) and (iii) (c) (i) and (iv) (ii) and (iv)

Soln: Answer is (d) (ii) and (iv) Explanation: Carbon compounds form covalent bonds hence they have very weak force of attraction. Carbon compounds are poor conductors of electricity.

ScienceClass 10CBSE

1. Carbon exists in the atmosphere in the form of (a) carbon monoxide only (b) carbon monoxide in traces and carbon dioxide (c) carbon dioxide only coal

Soln: Answer is (c) carbon dioxide only

ScienceClass 10CBSE

A sulphate salt of Group 2 element of the Periodic Table is a white, soft substance, which can be moulded into different shapes by making its dough. When this compound is left in open for some time, it becomes a solid mass and cannot be used for moulding purposes. Identify the sulphate salt and why does it show such a behaviour? Give the reaction involved.

Soln: The sulphate salt should be calcium sulphate which is white and soft substance. Calcium sulphate is popularly known as plaster of paris. Plaster of paris has half molecule of water of crystallization. When we leave plaster of paris open for some time, it absorbs moisture to gain number of molecules of crystallization. This newly formed compound is called Gypsum which is hard to make moulds.

ScienceClass 10CBSE

A dry pellet of a common base B, when kept in open absorbs moisture and turns sticky. The compound is also a by–product of chloralkali process. Identify B. What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.

Soln: A compound which is a byproduct of chloralkali process is NaOH. Hence compound B is NaOH. When NaOH is treated with acidic oxide neutralization process occurs. For Example If NaOH is treated with carbon-di-oxide, it gives Sodium carbonate. 2NaOH+ CO2 Na2CO3+ H2O

ScienceClass 10CBSE

A metal carbonate X on reacting with an acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y, it gives a compound Z, used for disinfecting drinking water. Identity X, Y, G and Z.

Soln: X is Calcium . When calcium carbonate reacts with HCl it gives out CO2 gas. CaCO3 + HCl CaCl2+CO2+H2O When CO2 is passed into lime water it turns milky due to formation of Calcium carbonate. Hence solution Y is lime water When chlorine gas is passed on dry lime water it gives bleaching powder which is used for disinfecting water.

ScienceClass 10CBSE

When zinc metal is treated with a dilute solution of a strong acid, a gas is evolved, which is utilised in the hydrogenation of oil. Name the gas evolved. Write the chemical equation of the reaction involved and also write a test to detect the gas formed.

Soln: When Zinc reacts with Dilute acid solution, following reaction takes place Hydrogen gas is evolved Zn + 2HCl ZnCl2 + H2 When Hydrogen gas is brought near Burning flame, pop pops up which is the confirmation for evolution of Hydrogen gas.

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