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2101.

What is catenation ?

Answer»

Solution :It is the PROPERTY of carbon to LINK with other carbon atom FORMING STRAIGHT chain, branched chain or ring compounds.
Discussion
2102.

What is meant by combination reaction?Give example.

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Solution :A reaction in which SINGLE product is formed from two or more REACTANTS is KNOWN COMBINATION reaction .
`2Mg+O_(2)to2MgO`
Discussion
2103.

We can expect that pure water ________ normally conduct electricity . (will /will not)

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SOLUTION :will not
Discussion
2104.

Which of the following has double bonds ?

Answer»

ETHANE and oxygen
NITROGEN and ethane
oxygen and methane
ethene and carbon DIOXIDE

ANSWER :D
Discussion
2105.

Which elements has Twice as many electrons in its second shell as in its first shell ?

Answer»

Solution :CARBON has twice the NUMBER electrons in its SECOND SHELL than the first shell
Discussion
2106.

Two elements M and N belong to the same period of the modern periodic table and are in group I and group II respectively. Compare their following properties : Atomic size (b) Metallic character ( c) Valency of oxides (d) Molecular formula of their chlorides

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Solution : ELEMENT .M. has LARGER atomic SIZE than that of .N..
(b) Element .M. possess more metallic character than that of .N..
(C) Group 1: VALENCY: 1
Group II : Valency: 2
(d) MCI, `MCI_(2)`
Discussion
2107.

What is hetero atomic molecule ? Give two example.

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SOLUTION :The molecule that consist of atoms of DIFFERENT elements is CALLED heteroatomic molecule.
e.g. HCI, `H_(2)O`
Discussion
2108.

Zinc piece and zinc powder are taken in two test tubes and equal amount of dil. HCl is added. Give the reason.

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ANSWER :Total SURFACE area increases on powdering. So the RATE of EFFECTIVE collsions increases.
Discussion
2109.

Translate the following statements into chemical equations and balance them. Hydrogen sulphide gas burns in air to give water and sulphur dioxide.

Answer»

Solution :`2H_(2)S(G)+3O_(2)(g) to 2H_(3)O(L)+2SO_(3)(g)`
Discussion
2110.

Which of the following indicators is the best indicator for the detection of end point in the titration of CH_(3)COOH and KOH ?

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METHYL organge
phenolphthalein
methyl red
none of these

Answer :B
Discussion
2111.

Which of the following statements is valid for a compound ?

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It is HETEROGENEOUS throughout .
Its COMPOUNDS are visible to the naked EYE.
It MELTS at a definte temperature .
none of the above

Answer :C
Discussion
2112.

What is meant by atomic radius ? Explain why it decreases across a period ?

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Solution :The distance from centre of nucleus to outermost shell of an atom is atomic radius.
Atomic radius DECREASES across a period because electron is added in the same shell. So attraction between nucleus and VALENCE shell INCREASES due to which outermost shell is pulled in closer to the nucleus.
Discussion
2113.

Which metal is used in semiconductor devices ?

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SOLUTION :GERMANIUM.
Discussion
2114.

What happens when methane is burnt in air?

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SOLUTION :Methane BURNS in air to GIVE carbon DIOXIDE and water.
`CH_(4)+2O_(2) to CO_(2) +2H_(2)O+` Heat energy
Discussion
2115.

What happens when (give balanced equations): Ethene combines with hydrogen chloride.

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SOLUTION :`CH_2 = CH_2 + H - CL to CH_3 CH_2Cl`
Discussion
2116.

What is the colour of methyl orange in baking soda ?

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SOLUTION :COLOUR of METHYL ORANGE will be YELLOW.
Discussion
2117.

Write the balanced equation for the chemical reactions : Sodium + Water to Sodium hydroxide + Hydrogen

Answer»

Solution :`2Na(s)+ 2H_(2)O(I) to 2NAOH(AQ)+H_(2)(G)`
Discussion
2118.

What would you observe when Zinc is added to a solution of iron (II) Sulphate. Write the chemical reaction that takes place.

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Solution :When zinc is added to a solution of iron (II) SULPHATE it will DISPLACE iron from it and light GREEN colour of solution GRADUALLY fades away.
`Zn+FeSO_(4)toZnSO_(4)+Fe`.
Discussion
2119.

Which acid is produced in our stomach ? What happens if there is an excess of acid in the stomach ? How can its effect be cured ?

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Solution :Hydrochloric acid is produced in our STOMACH. The excess acid in the stomach CAUSES indigestion which produces pain irritation. This effect can be cured by using antacids. Antacids (a group of mild bases ) react with excess acid in the stomach and NEUTRALISE it.
Discussion
2120.

Which of the following is an example of a homogeneous mixture ?

Answer»

POTASH ALUM in water
OIL and water
SEA water
Air

Answer :A
Discussion
2121.

The volume occupiedby onemoleof anygasat STPis calledas _______.

Answer»

SOLUTION :Molarvolume
Discussion
2122.

Write the balanced chemical equation and identify the type of reaction in each case. Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine.

Answer»

Solution :`Cl_(2)(G)+2KL(AQ.)to2KCl(aq.)+l_(2)(s)`
Discussion
2123.

Which of the following compounds behave as an unsaturated hydrocarbon ?

Answer»

BUTANE
ethane
ethylalcohol
ETHENE

Solution :ethene
Discussion
2124.

Write the chemical name and formula of common salt. List two main sources of common salt in nature. Write any two uses of common salt. How is it connected to our struggle for freedom?

Answer»

Solution :Sodium chloride NaCl.
COMMON salt from sea water and Rock salt.
Uses of common salt:
(i) As a raw material for making a large number of useful chemicals in industry as sodium hydroxide, sodium bicarbonate, sodium carbonate, hydrochloric acid.
(ii) Used in cooking food. It is ESSENTIAL in our food for the paper functioning of nervous system, the movement of muscles and the production of HCl in our stomach for the digestion of food.
(III) Used as a preservative in pickles.
(iv) Used in the manufacture of soap.
MAHATMA gandhi Dandi march was for the procurement of common salt for common man.
It is the most essential product of daily use.
Discussion
2125.

While constructing a house, a builder selects marble flooring and marble table top for the kitchen where vinegar and juices of lemon tamarind etc., are more often used for cooking. Will you agree to this selection and why?

Answer»

Solution :No, this selection is wrong.
Vinegar and juices of LEMON, tamarind etc., are acidic solutions. ACIDS react with MARBLE flooring and marble table top. Marble is CALCIUM carbonate which reacts with acids. For example,
`CaCO_3 +underset("Vinegar")(2CH_3COOH) rarr underset("Calcium acertate")((CH_3COO)_2)Ca+CO_(2)+H_(2)O`
Discussion
2126.

What are functional groups ? Give examples.

Answer»

Solution :An atom or a group of atoms which imparts specific properties to the compound is CALLED a functional group.
Chemical REACTIONS of different organic compounds containing same functional group are same.
Chemical reactions and properties of organic compounds containing different functional groups are different.
FREE valency or valencies of the group are shown by the single line ( - ).
The functional group is attached to the carbon CHAIN by replacing one or more hydrogen atom or atoms.
Examples: Some examples of functional groups are as follows:
Discussion
2127.

Write the balanced chemical equations for the followingreactions. (a) Calcium hydroxide +Carbon dioxide →Calcium carbonate +water (b) Zinc +Silver nitrate→Zinc nitrate +Silver (c) Aluminium + Copper cloride → Aliminium chloride +Copper (d) Barium chloride + Potassium sulphate→ Barium sulphate + Potassium chloride

Answer»

Solution :(a) `CA(OH)_(2)+CO_(2)rarrCaCO_(3)+H_(2)O`
(b) `Zn+2AgNO_(3)rarrZn(NO_(3))_(2)+2AG`
(C) `2Al+3CuCl_(2)rarr2AlCl_(3)+3Cu`
(d) `BaCl_(2)+K_(2)SO_(4)rarrBaSO_(4)+2KCl`
Discussion
2128.

What happens when a small amount of baking soda is taken in a test tube and some dilute hydrochloric acid is added to it ?

Answer»

A RAPID reaction OCCURS but no gas evolves
A BLUE - coloured solution is obtained
A BRISK efferevescence occurs with the EVOLUTION of carbon dioxide gas
hydrogen gas is produced

Answer :C
Discussion
2129.

Which one of the following solutions will not turn blue litmus red?Lemon juiceAcetic acidSodium hydroxideHCl

Answer»

LEMON juice
Acetic acid
Sodium hydroxide
HCl

Answer :C
Discussion
2130.

Whenthe reactionmixtureis heatedthe reactionrate _________.

Answer»

SOLUTION :INCREASES
Discussion
2131.

What is an exothermic reaction? Which of the following is an exothermic reaction? i) Heating calcium carbonate ii) Adding water to calcium oxide

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SOLUTION :i) The chemical reactions in which heat is evolved (or given out) during the REACTION are called exothermic reactions.
ii) Adding water to calcium OXIDE.
Discussion
2132.

What is the valency of elements with atomic number 8, 14, 17 and 20?

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SOLUTION :
Discussion
2133.

Which amongst the given metals forms water soluble product after heating it ?

Answer»

Solution : AMONGST the GIVEN METALS, only sodium metal on heating FORMS OXIDE which is soluble in water
Discussion
2134.

Write the actual product of 4.32 xx2.8

Answer»

12.096
12.09
12.08
12

Answer :D
Discussion
2135.

What is meant by "the hydrogenation of vegetable oils"? Write the chemical reactions involved in the process. State differences between oils and fats.

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SOLUTION :For hydrogenation of vegetable oils AD CHEMICAL EQUATION, Differences betwween oils and fats are given.
.
Discussion
2136.

What happens to food contining fat and oil kept open for a long time?

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Solution :When FOOD CONTAINING fat and oil is left as such for a LONG time ,it becomes stale.The stale food DEVELOPS bad taste and foul smell.This is very common and cheese particularly in summer.Oils and fats ate slowly fats are slowly oxidised to certain foul smelling compounds.
Discussion
2137.

You are given a hammer, a battery, a bulb, wires and a switch. (a) How could you use them to distinguish between samples of metals and non-metals ? (b) Assess the usefulness of these tests in distinguishing between metals and non-metals ?

Answer»

Solution :
(a) Place the SAMPLE on an iron block. Strike withhammer. If the sample takes the shape of a sheet, it is a metal. If it breaks into pieces, it is a non-metal. Set up an arrangement by using a bulb, a battery,wires and a SWITCH . Insert the samples ofmetals and non-metals in the clips one by one andturn the switch on. If the bulb glows, the sample isa metal. If not, then the sample is a non-metal.
(b) The above TWO methods can, in general, be used to distinguish between metals and non-metals.But there are some exceptions. For example, GRAPHITE, which is a form of CARBON, a non-metal,is a conductor of electricity.
Discussion
2138.

When a drop of a solution X is added to the universal indicator, a deep red colour is produced. Which one of the following is this sample?

Answer»

SODIUM hydroxide
Hydrochloric acid
Distilled water
Acetic acid

Answer :B
Discussion
2139.

Whichof thefollowingstatementregardingan atom isalwayscorrect?

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An ATOM hasequalnumberof electronsandprotons
An ATOMHAS equalnumberof electronsandneutrons
Anatomhasequalnumberof electronsprotonsandneutrons
An atom has equalnumberof protonsandneutrons

ANSWER :A
Discussion
2140.

What would be the colour of a moistened red litmus paper when it is brought in contact with the ash produced after the burning of magnesium ribbon in air ?

Answer»

SOLUTION :Red litums PAPER will turn BLUE.
Discussion
2141.

Which of the following statements are true for acids ?

Answer»

Bitter and change RED LITMUS to blue
Sour and change red litmus to blue.
Sour and change blue litmus to red.
Bitter and change blue litmus to red

Solution :Acids possess sour TASTE and TURN blue litmus PAPER red.
Discussion
2142.

Write the names of the next homologue of CH_3CH_2OH and HCOOH.

Answer»

SOLUTION :PROPANOL and ACETIC ACID.
Discussion
2143.

What is the colour of anhydrous copper sulphate ?

Answer»

SOLUTION :COLOURLESS.
Discussion
2144.

What happens when a) ethanol is burnt in air and b)ethanol is oxidized? Write the corresponding equations.

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SOLUTION :a) Ethanol burns in the presence of OXYGEN to GIVE carbon DIOXIDE.
`CH_3CH_2OH + 3O_2 to 3H_2O + 2CO_2`
b] Ethanol undergoes oxidation giving ETHANOIC acid.
Discussion
2145.

What is the molecular formula of the compound?

Answer»

SOLUTION :The MOLECULAR FORMULA is `C_4H_10`
Discussion
2146.

Explain the term pH of a solution . What is pH of blood ?

Answer»

SOLUTION :The pH of a solution is defined as the negative logarithm of the HYDROGEN ion CONCENTRATION of the solution . i.e, pH = -log `[H^(+)]`
Discussion
2147.

Volume of gas at STP is 1.12xx10^(-7)c c. Calculate the number of molecules in it.

Answer»

`3.011xx10^(20)`
`3.011xx10^(12)`
`3.011xx10^(23)`
`3.011xx10^(24)`

SOLUTION :`3.011xx10^(12)`
Discussion
2148.

Write the chemical equations to represent the oxidation of ethanol and name the reactants and products.

Answer»

SOLUTION :`UNDERSET("ETHANOL")(CH_3CH_2OH)OVERSET([O])(to) underset("ETHANAL")(CH_3CHO) overset([O])(to) underset("ethanoic acid")(CH_3COOH)`
Discussion
2149.

Which of the following is a triatomic molecule?

Answer»

Glucose
Helium
Carbon DIOXIDE
HYDROGEN

Solution :Hint : (a) `"Glucose"=C_(6)H_(12)O_(6)" (Poly atomic molecule)"`
(b) `"Helium"=He"(MONO atomic molecule)"`
(c ) `"Carbon dioxide "=CO_(2)" (Triatomic molecule)"`
(d) Hydrogen `=H_(2)"(Diatomic molecule)"`
Discussion
2150.

What is the advantage of disposable paper cups over disposable plastic cups ?

Answer»

Solution :DISPOSABLE paper cups are biodegradable as they are degraded by saprophytic bacteria and fungi. The disposable PLASTIC cups remain in the ENVIRONMENT for longer period of TIME causing pollution as they are non-biodegradable.
Discussion