Class X 10 ONE Mark Chemistry Questions: Do you know the Answers?

CHEMICAL REACTIONS

Q1.   Balance the following chemical equation:

 Pb(NO3)2(s) ─heat→ PbO(s) + NO2 (g) + O2 (g)

Q2.  Write a balanced chemical equation for the reaction between sodium carbonate and hydrochloric acid indicating the physical state of the reactants and the products.

Q3.  Name a reducing agent that may be used to obtain manganese from manganese dioxide.

Q4.  Why do potato chips manufacturers fill the packet of chips with nitrogen gas?

Q5.  What is the valency of silicon with atomic number 14?

ACIDS, BASES AND SALTS

Q6.  Fresh milk has a pH of 6.  When it changes into curd (yoghurt) will its pH value increase or decrease? Why?

Q7.  During the summer season, a milkman usually adds a very small amount of baking soda to fresh milk. Give one reason.

Q8.  A drop of litmus solution is added to each of the four solutions given below.  State the colour of litmus solution observed in each: soap solution, sodium carbonate solution, vinegar, lemon juice.

METALS & NON-METALS

Q9.  The surface of some metals loses their brightness when kept in air for a long time. Why?

Q10. What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes?

Q11. Metals generally occur in the solid state. Name and write symbol of a metal that exists in a liquid state at room temperature.

Q12. Write a balanced chemical equation to represent the following reaction:  Iron reacts with stream to form Iron (II, III) oxide with hydrogen gas.

CARBON COMPOUNDS

Q13. State two characteristic features of carbon which when put together give rise to a large number of carbon compounds.

Q14. Write the structural formula of chloroethane.

Q15. Draw the electron-dot structure of ethane molecule (C2H6).

Q16. Write the number of horizontal rows in the modern periodic table.  What are these rows called?

Q17. Write the name and formula of the 2nd member of homologous series having general formula CnH2n.

Q18. Name the process of converting vegetable oil to vegetable ghee.

Q19. Write the molecular formula of (i) Methane and (ii) Ethanol.

Q20. Write the name of the first two members of homologous series having a functional group –OH.

Q21. Butanone is a four-carbon per molecule compound. Note the functional group present in it.

PERIODIC CLASSIFICATION OF ELEMENTS

Q22. State Modern Periodic Law of classification of elements.

Q23. The atomic number of sodium is 11, fluorine is 9 and neon is 10.  Why are sodium and fluorine very reactive while neon shows almost no reactivity.

X_Chemistry_1 Mark_Answers

Class X Chemistry: Soaps & Detergents

Soaps are sodium or potassium salts of long-chain fatty acids [carboxylic acids -Stearic acid, palmitic acid or oleic acid].

Saponification: The process in which oil or fat is hydrolyzed with Sodium hydroxide to get soap and glycerol is called saponification. The ionic-end of soap dissolves in water while the carbon chain dissolves in oil.

Types of Soap: Depending upon the nature of alkali used in the production of soap, they are classified into two types.

a) The sodium salt of long chain fatty acid is known as hard soap. It is difficult to dissolve in water. It is used as laundry soap.

b) The potassium salt of long chain fatty acid is known as soft soap, as it produces more lather. It is used as toilet soap and shaving soap.

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Class X Chemistry: Carbon Compounds

FUNCTIONAL GROUP

Functional Group – Single atom or group of atoms, that have similar chemical properties are called functional group. For example Halogen group, Carboxyl group, Aldehyde group, etc. These functional groups confer specific properties to the compound, regardless of the length and nature of the carbon chain. Functional Group is a heteroatom.

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Class X Chemistry: Hydrocarbons

HYDROCARBONS

 Hydrocarbon means compounds of Hydrogen and Carbon

 Hydrocarbons are to only of two types – Saturated Hydrocarbons and Unsaturated Hydrocarbons.

 Saturated and Unsaturated Hydrocarbons can be Chains, Branches, and Rings

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Class X Chemistry: Carbon

CARBON – AN UNIQUE ELEMENT

Atomic No.: 6
Electronic Configuration: 2, 4
Valency: 4

1. Any element having 6 protons in the nucleus is CARBON. The Atomic number of Carbon is 6.

2. Carbon is formed by the fusion of hydrogen atoms inside stars.

3. Carbon has 4 electrons in its valency shell. To attain noble gas configuration, carbon shares these 4 electrons by forming covalent bonds.

4. The compounds of carbon have a 3-dimensional shape as the electron cloud in the four bonds remain far apart by repulsion.

5. Allotropy: Allotropy is the property of an element to exist in more than one physical forms. Physical form which differs in the arrangement of atoms. Elements like tin, carbon, sulphur, phosphorus and oxygen exhibit allotropy.  Diamond, Graphite, and Fullerene are allotropes of Carbon.

allotroph of carbon

6. Carbon with Nitrogen, Oxygen or Hydrogen forms various compounds like carbohydrates, proteins, DNA etc which are building blocks of life. These categories of compounds are organic compounds. Carbon is key to life on Earth. Man is a carbon-based life form.

VERSATILE NATURE OF CARBON

Two factors –

(i) Catenation – Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called catenation.

(ii) Tetra-Valency – Since carbon has a valency of four, it is capable of bonding with four other atoms of carbon or atoms of some other mono-valent element.

COMPOUNDS OF CARBON

1. Organic Compounds – Initially, compounds of carbon could only be obtained from living sources and therefore known as organic compounds. In organic compounds, one or more atoms of carbon are covalently linked to atoms of other elements most commonly Hydrogen, Oxygen or Nitrogen.  Urea is the first compound synthesized in 1828 by Friedrich Wohler. So far, formulae of about 3 million carbon compounds are known.Traditionally Carbonates, carbides, oxides of carbon and Cyanides are considered inorganic compounds.

2. Hydro Carbons – Compounds of Hydrogen and Carbon is a particular category of Organic Compounds which are the source of all fossil fuels. Hydrogen has valency 1 and therefore attach to all of the 4 valency electrons of Carbon by forming covalent bonds (formed by sharing of electrons)

3. Saturated Carbon Compounds – Compounds of carbon, which are linked by only single bonds between the carbon atoms are called saturated compounds. Valencies of all the atoms are satisfied by single bonds between them. Such carbon compounds are called saturated compounds. These compounds are normally not very reactive. Saturated hydrocarbons are known as ALKANE. These are also known as paraffin. Example: Methane, Ethane, Propane, etc.

4. Unsaturated Carbon Compounds – Compounds of carbon having double or triple bonds between their carbon atoms are called unsaturated compounds. They are more reactive than the saturated carbon compounds.

(i) Hydrocarbon with double bond: Hydrocarbons having at least one double bond are known as ALKENE. Example: Ethylene, Propylene, Butylene, etc.

(ii) Hydrocarbon with triple bond: Hydrocarbons having at least one triple bond are known as ALKYNE. Example: Ethyne, Propyne, Butyne, etc.

5. Functional Group – Single atom or group of atoms, that have similar chemical properties are called functional group. For example Halogen group, Carboxyl group, Aldehyde group, etc. These functional groups confer specific properties to the compound, regardless of the length and nature of the carbon chain. The functional group is attached to the carbon chain by replacing one hydrogen atom or atoms.

6. Homologous Series – Series of compounds with same general formula and functional group is known as homologous series. Compounds belonging to the same homologous series show similar properties. Compounds of homologous series differ by -CH2 from their consecutive members. Compounds of same homologous series differ by physical properties with increase or decrease in molecular mass.

COVALENT BONDING

Covalent Bond: A covalent bond is a chemical bond formed by sharing of electron pairs between atoms. The key to understanding covalent bond is Electronegativity – The tendency of an atom or molecule to attract electrons and form bonds. Two atoms with similar electro-negativity will not exchange an electron from their outermost shell. The atoms instead share electrons so their valency shell is filled. Covalent bonds occur between on-metals or between two of the same (or similar) elements.

Properties of Covalent Bonds:

a) States: Covalent compounds exist mostly in gaseous state (hydrogen, oxygen, ammonia) or liquid(bromine) and few as solids (iodine, phosphorus)

b) Melting and Boiling points: Covalent compounds have usually low melting and boiling point as the molecules are held by weak forces. These can easily be overcome by heat.

c) Non-conducting nature: Covalent compounds are poor conductors of electricity as they do dissociate into ions.

d) Solubility: Covalent compounds are not soluble in water(polar solvent). They dissolve in non-polar solvent like carbon tetrachloride, Benzene etc.

e) Isomerism: Covalent bonds are rigid and directional. Therefore, these can give different arrangement of atoms in space. So, a single molecular formula may represent a number of different compounds with different properties. This phenomenon is called ISOMERISM.

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Class X Chemistry: Classification of Elements

The periodic table is a tabular arrangement of the chemical elements, organized on the basis of their atomic numbers, electron configurations (electron shell model), and recurring chemical properties. The principle here is a gradation of properties of elements and similar elements are placed together.

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Class X Chemistry: Metallurgy

The earth’s crust is the major source of metals. Seawater also contains some soluble salts such as sodium chloride, magnesium chloride, etc.

Minerals: The elements or compounds, which occur naturally in the earth’s crust, are known as minerals.

Ores: The minerals from which a metal can be profitably extracted are called ores.

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Class X Chemistry: Ionic Compounds

Many metals form ionic bonds when they react with non-metals. Compounds so formed are known as ionic compounds.

Ions: Positive or negative charged atoms are known as ions. Ions are formed because of loss or gain of electrons. Atoms form ion to obtain the electronic configuration of nearest noble gas, this means to obtain stable configuration.

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