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2001.

Whatmassofhydrogenand oxygenwill beproducedon completeelectrolysisof18gofwater

Answer»

2 ghydrogenand32 G OXYGEN
2 g hydrogenand 16h oxygen
4 g hydrogenand32g oxygen
4 ghydrogenand 14ocygen

ANSWER :B
Discussion
2002.

What are active metals? Give examples with equations.

Answer»

SOLUTION :A METAL that can DISPLACE hydrongen from an ACID is called an ACTIVE metal.
Discussion
2003.

When rain is accompanied by a thunderstorm, the collected rain water will have a pH value

Answer»

lower than rainwater WITHOUT LIGHTNING
HIGHER than rainwater without lightning
unchanged
none of the above

ANSWER :A
Discussion
2004.

What is chemical combination reaction ?

Answer»

Solution :When TWO or more SUBSTANCES combine to from a single product, the reactions are CALLED COMBINATION reactions.
Discussion
2005.

Three elements X, Y and Z have atomic numbers 7, 10 and 14 respectively. (i) Identify the group number of these elements in the periodic table. (ii) Mention one unique feature each of elements Y and Z. (iii) Which of the above two elements belong to the same period ?

Answer»

Solution :(i) X - 2, 5 : Group 15
Y - 2, 8 : Group 18
Z - 2, 8, 4 : Group 14
(ii) Y is a noble gas which is unreactive and has COMPLETE outermost SHELL.
Z is metalloid and possesses semi-metal, properties of both metals and non-metals.
(iii) X and Y belong to the same PERIOD i.e., `2^(nd)` period.
Discussion
2006.

Which property of graphite is utilised in making electrodes?

Answer»

SOLUTION :Graphite is a GOOD CONDUCTOR of electricity. Due to this property, graphite is UTILISED in making electrodes.
Discussion
2007.

What is double displacement reaction ? Explain with the help of an example.

Answer»

Solution :A CHEMICAL reaction in which exchange of iron takes place between two COMPOUNDS to form new compounds is called double displacement reaction.
Example : When aqueous solution of Sodium SULPHATE and barium chloride are added or mixed, ion exchange takes place to form Barium sulphate and Sodium chloride :
`Na_(2)SO_(4)(aq)+BaCl_(2)(aq)toBaSO_(4)+2NaCl(aq)`.
Discussion
2008.

Write the molecular formula of the following compounds and draw their electron-dot structures : (i) Ethane (ii) Ethene (iii) Ethyne

Answer»

SOLUTION :(i) Ethane : `C_(2)H_(6)`
Discussion
2009.

Which among the following is an oxide ore of lead?

Answer»

LED ochre
galena
anglesite
dolomite

Answer :A
Discussion
2010.

You must have tasted or smelt the fat containing food material left for a long time. Such foods taste and smell bad. What is the reason for the reason for this ? Name to the phenomenon responsible for it. List two measures for its prevention.

Answer»

Solution :Food material left for a long time is oxidised by atmospheric oxygen. This changes the SMELL and taste of food.
Measures for PREVENTION :
(i) Keep the food in AIR -- tight containers.
(ii) Flush the food packets with nitrogen GAS before SEALING.
Discussion
2011.

When magnesium is burnt in oxygen , the compound formed is

Answer»

megnesium PEROXIDE
MAGNESIUM OXIDE
magnesium nitrate
magnesium chloride

Answer :B
Discussion
2012.

The substances that cause pollution are called_____\

Answer»

SOLUTION :PHYSICAL, BIOLOGICAL
Discussion
2013.

What are amphoteric oxides ? Give two examples of amphoteric oxides.

Answer»

Solution :Metal oxides which show both acidic as well as BASIC BEHAVIOUR are called amphoteric oxides. Suchmetal oxides react both with ACIDS and bases.
Examples : Aluminium OXIDE `(Al_2O_3)`
ZINC oxide (ZnO)
Discussion
2014.

Give reasons: Aluminium alloys are used to make aircraft body.

Answer»

Solution :(i) Property of ALUMINIUM.
(II) Comparison of PROPERTIES of METAL and its ALLOY.
Discussion
2015.

What happens when crystals of lead nitrate are heated strongly in a dry test tube ?

Answer»

CRYSTALS MELT immediately.
Brown fumes are obtained.
White fumes get formed in the test tube.
Yellow PRECIPITATES are obtained.

Solution :Brown fumes are obtained.
Discussion
2016.

What is aqua regia

Answer»

SOLUTION :It is a FRESHLY prepared mixture of concentrated hydrochloric acid and concentrate nitric acid in the ratio of `3:1`. UT CAB dissolve GOLD. It is a highly corrosive liquid,
Discussion
2017.

Which one of the following is more reactive element?

Answer»

Cu
LI
Zn
Pb

Answer :Li
Discussion
2018.

Using the part of the Periodic Table given below, answer the questions that follow: (i)Na has physical and chemical properties similar to which element (s) and why? (ii) Write the electronic configuration of N and P. Which one of these will be moreelectronegative and why?(iii) State a chemical property common to fluorine and chlorine.

Answer»

Solution : (i) Lithium and potassium, due to same number of valence ELECTRONS.
(ii) `N to 2, 5`
`P to 2,8,5`
N is more ELECTRONEGATIVE element as electronegativity decreases on MOVING down thegroup.
(iii) Both fluorine and chlorine form their hydracids on REACTING with hydrogen.
`H_2 + F_2 to 2HF`
`H_2 + Cl_2 to 2HCl`
Discussion
2019.

What is an alkail ?

Answer»

SOLUTION :An alkali is a base that dissolves in WATER ,i.e,a water- SOLUBLE base is called an alkail.
Discussion
2020.

A 4cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 24 cm. the distance of the object from the lens is 16 cm. Find the position, size and nature of the image formed using the lens formula.

Answer»

Solution :The ray which stricks the mirror surface ncar the periphery are called marginal rays for comer lens. f = -24 cm. u= 16 cm using lens FORMULA
`(1)/(f)= (1)/(v) =(1)/(u)`
`(1)/(24)= (1)/(v)- (1)/(-16)= (2-3)/(48)= (-1)/(48)`
V= -48 now `h_(1)= 4 cm`
so magnitication.`m= (h_(2))/(h_(1))= (v)/(u)`
`h_(2)= (v)/(u) xx h_(1)= (-48)/(-16) xx 4= 12 cm`
The image is formed at a distance of 48 cm from the optical focus of the lens on the same SIDE of the object. This is indicated by the negative SIGN. Size of image is three TIMES the size of objec i.e 12 cm.
Nature of image: Positive sign in the image height indicates that image is virtual and erect.
Discussion
2021.

What is a redox reaction ? When a magnesium ribbon is burnt in air, it burns with a dazzling white flame and white powder is formed. Is magnesium oxidised or reduced ? Why ?

Answer»

Solution :A REACTION in which oxidation and reduction reactions occur simultaneously is called REDOX reaction.
`2Mg(s) + O_(2)(g) to2MgO(s)`
In this reaction, magnesium COMBINE with oxygen. Hence, it is oxidised to MGO.
Discussion
2022.

What are themajorclassesof doubledisplacementreactions ?

Answer»

SOLUTION : (i)PrecipitationReactions
(II )NeutralizationReactions
Discussion
2023.

What are the indicators called if they emitdifferent odours when added to acids and bases ?

Answer»

SOLUTION :OLFACTORY INDICATORS.
Discussion
2024.

Which of the following is appreciably soluble in water?

Answer»

`CS_(2)`
`C_(2)H_(5)OH`
`C Cl_(4)`
`CHCl_(3)`

Answer :B
Discussion
2025.

Translate the following statements into chemical equations and then balance them : Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

Answer»

Solution :`{:(" "K(s)+H_(2)O(l)toKOH(aq)+H_(2)(G)"(Unbalanced equation)"),(2K(s)+2H_(2)O(l)to2KOH(aq)+H_(2)(g)"(BALANCED equation)"):}`
Discussion
2026.

What is esterification?

Answer»

Solution :The REACTION of an ALCOHOL with a carboxylic acid in the PRESENCE of concentrated sulphuric acid gives an ESTER.
Discussion
2027.

Which one of the following has the smallest atomic radius?

Answer»

Lithium
FLUORINE
POTASSIUM
CHLORINE

SOLUTION :Fluorine
Discussion
2028.

When SO_(2) gas is passed through an acidified solution of K_(2)Cr_(2)O_(7) the orange colour of the solution changes to

Answer»

red
orange
green
black

Answer :C
Discussion
2029.

Which of the following is not a decomposition reaction ?

Answer»

`CaCO_(3) toCaO + CO_(2)`
`2KCIO_(3) to 2KCI + 3O_(2)`
Disgestion of food in BODY
`H_(2) + Cl_(2) to 2HCI`

Answer :C
Discussion
2030.

Write the molecular formula of the third member of the homologous series represented by the general formula C_(n)H_(2n+1)OH

Answer»

Solution :`C_(3)H_(7)OH`
Discussion
2031.

Which of the following are exothermic reactions ? (i) Evaporation of water (ii) Dilution of H_(2)SO_(4) (iii) Reaction of water with quick lime (iv) Sublimation of crystalline camphor

Answer»

(i) and (II)
(III) and (IV)
(i) and (iv)
(ii) and (iii)

SOLUTION : (ii) and (iii)
Discussion
2032.

The structural formula of an ester is: H-underset(H)underset(|)overset(H)overset(|)C-overset(O)overset(||)C-O-underset(H)underset(|)overset(H)overset(|)C-underset(H)underset(|)overset(H)overset(|)C-H Write the molecular formula of alcohol and acid from which it would have been formed.

Answer»

SOLUTION :Alcohol `to CH_(3)CH_(2)OH//C_(2)H_(5)OH`
Carboxylic acid `to CH_(3)COOH`
Discussion
2033.

Write the name, symbol and electronic configuration of an element X whose atomic number is 11.

Answer»

Solution : ‘X. is SODIUM
Its symbol is NA Its ELECTRONIC CONFIGURATION is 2,8,1.
Discussion
2034.

What would be the electron dot structure of carbon dioxide which has the formula CO_2 ?

Answer»

SOLUTION :
Discussion
2035.

There is no change in the colour of red litmus and blue litmus paper when introduced into an aqueous solution of sodium chloride. After passing direct current through the same solution, red litmus changes to blue colour. Which product is responsible for this change ? Mention any two uses of this product.

Answer»

Solution :Sodium hydroxide/NaOH
(i) De-greasing metals
Soaps and detergents
(III) Paper making
(IV) ARTIFICAL FIBRES
Discussion
2036.

What colour does Na, Mg, Cu and Al impart to the oxidising flame?

Answer»

SOLUTION : Na `to` YELLOW FLAME
Mg `to`Dazzling WHITE flame
Cu `to`Greenish blue flame
Al `to`White flame
Discussion
2037.

Which of the following reactions is not correct?

Answer»

`2AgNO_(3) + Cu to Cu(NO_(3))_(2) + 2AG`
\(C1_{2} + 2KI \rightarrow KCl + I_{2}\)
`FeSO_(4) + Cu to CuSO_(4) + FE`
`CuSO_(4) + ZN to ZnSO_(4) + Cu`

Answer :C
Discussion
2038.

Which one of the following metals do not react with cold as well as hot water ?

Answer»

Na
Ca
Mg
Fe

Solution :IRON REACTS with STEAM only.
Discussion
2039.

What is the type of reaction in which the reactant gives simpler products ?

Answer»


ANSWER :F
Discussion
2040.

Write the atomic numbers of two elements 'X' and 'Y' having electronic configuration 2, 8, 2 and 2, 8, 6 respectively.

Answer»

Solution :Atomic number of X = 2 + 8 + 2 = 12
Atomic number of Y = 2 + 8 + 6 = 16
Discussion
2041.

Which of the following statement regarding pi bond is not true?

Answer»

It may be formed by the overlapping of p-atomic orbitals
It has no independent existence
It is WEAKER bond compared to `SIGMA` bond
It is weaker bond compared to `sigma` bond

Answer :D
Discussion
2042.

The watershed management

Answer»

Increases DROUGHT and floods
Increases PRODUCATION and income of the watershed community
Dccrcases the biodversity of the downstream reservoirs.
increases deforestation

Answer :2
Discussion
2043.

Write the molecular formulae of: CH_(3)Br and C_(2)H_(5)Br.

Answer»

SOLUTION :(a) `CH_(4)(G)+2O_(2)(g)toCO_(2)(g)+2H_(2)O(l)`
(b) `C_(2)H_(6)(g)+7//2O_(2)(g)to2CO_(2)(g)+3H_(2)O(l)`
Discussion
2044.

What is meant by reactivity or activity series of metals ? Arrange different metals in the decreasing order of their reactivity.

Answer»

Solution : When different METALS are arranged in decreasing ORDER of their reactivity (or ACTIVITY) then it constitutes a SERIES called reactivity (or activity) series of metals. Reactivity (or activity) series for different metals is given in the following Table :
Discussion
2045.

Which of the following are unsaturated compounds ? (i) Propane (ii) Propene (iii) Propyne (iv) Chloropropane

Answer»

(i) and (II)
(ii) and (IV)
(III) and (iv)
(ii) and (iii)

ANSWER :D
Discussion
2046.

What is locant number?

Answer»

Solution :Number the carbon atoms of the parent chain, beginning at the CLOSEST end of the SUBSTITUENT or functional GROUP. These are called locant numbers.
Discussion
2047.

Which of the following statements about the electron is incorrect?

Answer»

it is a NEGATIVELY CHARGED particle
the MASS of electron is equal to the mass of neutron
it is a BASIC constituent of all atoms
it is a constituent of cathode rays

Answer :B
Discussion
2048.

Which three chemical substances are obtained when electricity is passed through an aqueous solution of brine ? Write one industrial use of each.

Answer»

Solution :On passing electricity through an aqueous solution of brine, we obtain : SODIUM HYDROXIDE, Chlorine gas, Hydrogen gas
Industrial use :
Sodium Hydroxide – In MAKING SOAPS and detergents
Chlorine gas – Water treatment
Hydrogen gas – Fuel
Discussion
2049.

Write equations for the reactions of (i) iron with steam(ii) calcium and potassium with water.

Answer»

SOLUTION :
Discussion
2050.

Vanilla essence and olive oil are olfactory indicators.

Answer»


ANSWER :T
Discussion