8881 + Interview Questions in Chemistry in Class 10 Page 68 InterviewSolution

3351.	State reasons for the following : (a) Tap water conducts electricity, distilled water does not. (b) Dry hydrogen chloride does not turn blue litmus to red where as dilute hydrochloric acid does. (c ) During summer season, a milk man usually adds a very small amount of baking soda to fresh milk (d) For dilution of acid, acid is added into water and not water into acid. (e) Ammonia is a base but does not contain hydroxyl group.
Answer» Solution :(a) Tap water contains ions which conduct electricity whereas distilled water does not contain ions. (b) Dry HCl does not form ION but Hydrochloric acid gives `H^(+)` and `Cl^(-)` ions, this turns blue litmus to red. (c ) Baking soda does not allow milk to change to LACTIC acid which makes milk sour. (d) Adding water to acid is highly exothermic due to which the GLASS container may break. Therefore acid is ADDED to water very slowly with constant stirring to overcome heating. (e) Ammonia dissolves in water and form `OH^(-)` ions, therefore it is basic. `NH_(3) + H_(2)O rarr NH_(4)^(+) + OH^(-)`

Discussion

3352.	State reasons for the following: Electric wires are covered with rubber like material.
Answer» SOLUTION :It is because RUBBER is an sulator and does not ALLOW CURRENT ot FLOW through it.

Discussion

3353.	Whichof the following metalscannot liberate hydrogen from dilutehydrochloric acid
Answer» Solution :Zinc is more reactive than hydrogen. THEREFORE it can DISPLACE hydrogen from dilute HCL whereas copper cannot, because it is less reactive than hydrogen.

Discussion

3354.	State reason for the following statements : Tap water conducts electricity whereas distilled water does not
Answer» Solution :TAP water contains impurities of SALTS which are ionic COMPOUNDS. Hence tap water conducts ELECTRICITY. Distilled water does not contain impurities of salts, therefore, it does not CONDUCT electricity

Discussion

3355.	State reason for the following statements : For dilution of an acid, acid is added to water and not water to acid.
Answer» Solution :For dilution of the acid, we add acid to water and not water to acid. Addition of water to acid is an exothermic reaction. HEAT evolved when water is added to acid cannot be EASILY dissipated. However when we add acid to water in small amounts and with SHAKING, heat is dissipated SAFELY.

Discussion

3356.	State reason for the following statements : During summer season, a milkman usually adds a very small amount of baking soda to fresh milk.
Answer» Solution :Fresh milk gets SOURED in summer FORMING lactic ACID. Baking soda being basic in nature NEUTRALISES lactic acid and prevents souring of milk.

Discussion

3357.	State reason for the following statements : Dry hydrogen chloride gas does not turn blue litmus red whereas hydrochloric acid does.
Answer» Solution :WATER is NECESSARY for the REACTION with blue litmus. As dry hydrogen chloride gas does not contain water, colour change does not take PLACE. Hydrochloric ACID is a solution of hydrogen chloride gas in water.

Discussion

3358.	State reason for the following statements : Ammonia is a base but does not contain a hydroxyl group.
Answer» Solution :AMMONIA on DISSOLVING in water produces AMMONIUM hydroxide.

Discussion

3359.	State reason for the following : Potato chips manufacturers usually flush bags of chips with nitrogen gas.
Answer» Solution :Potato CHIPS contain OILS and fats, which react with atmospheric OXYGEN and become rancid. To PROTECT chips from OXIDATION, nitrogen gas is passed through bags of chips which removes air (oxygen) from them. Nitrogen does not react with chips.

Discussion

3360.	State reason for the following: (i) Lemon is used for restoring the shine of tarnished copper vessels. (ii) A metal sulphide is converted into its oxide to extract the metal from the sulphide ore. (iii) Copper wires are used in electrical connections.
Answer» Solution :(i) When copper VESSELS are exposed to moist air. They form a green coating of basic copper carbonate `[CuCO_3.Cu(OH)_2]` `2Cu+underbrace(CO_2+O_2+H_2O)_(From moist air)toCuCO_3.Cu(OH)2_(Basic copper carbonate (Green))` The sour substances such as lemon or tamarind juice contain acids. lemon juice contains citric acid and tamarind contains tartaric acid. These acids DISSOLVE the coating of copper oxide or basic copper sulphate present on the surface of tarnished copper vessels and MAKE them shining RED brown again. (ii) It is easier to obtain a metal from its oxides as compared to its sulphides and carbonates. So, prior to reduction, metal carbonate and sulphides must be converted into metal oxides. A carbonate ore is converted into oxide by calcination whereas a sulphide ore is converted into oxide by roasting. (iii) Copper wires are good conductors of electricity, so they are used in electrical CONNECTIONS.

Discussion

3361.	State reason for the following : Iron articles loose their shine gradually.
Answer» Solution :Iron article on keeping in the open for a LONG TIME REACTS with oxygen and MOISTURE and forms the rust on the surface. ARTICLES lose their shine because of this.

Discussion

3362.	State reason for the following : (i) Non-metals cannot displace hydrogen from the acids. (ii) Hydrogen is not a metal, yet it is placed in the activity series of metals. (iii) Aluminium is more reactive than iron, yet its corrosion is less than that of iron.
Answer» Solution :(i) Non-METALS are ELECTRON acceptors, they cannot supply electrons so as to convert `H^(+)` as ion to `H_(2)(g)`. (II) Like metals, hydrogen can lose an electron to form positive `H^(+)` ion. (iii) ALUMINIUM is covered with a strong protective layer of oxide which protects the metals from further corrosion.

Discussion

3363.	State reason for the following : Foods should be kept in air - tight containers.
Answer» Solution :Foods KEPT in the open are oxidised by the oxygen in AIR. Their TASTE and smell CHANGE. When kept in air - tight containers, the food does not COME into contact with air and is not spoilt.

Discussion

3364.	State Periodic Law on which the Modern Periodic Table is based.
Answer» SOLUTION :Modern Periodic Law based on ATOMIC number can be stated as “properties of the elements are periodic function of their atomic number.” That is, in the Modern Periodic Table, the elements are arranged in the ORDER of their INCREASING atomic numbers.

Discussion

3365.	State Periodic Law on which the Modem Periodic Table is based.
Answer» Solution :PROPERTIES of an ELEMENT are PERIODIC function of ATOMIC number.

Discussion

3366.	State one use of anhydrous calcium chloride.
Answer» Solution : Anhydrous calcium CHLORIDE is USED as drying agent, because it ABSORBS moisture from the AIR.

Discussion

3367.	State three reasons for placing chlorine and bromine in the same group of the periodic table.
Answer» SOLUTION :Due to the presence of 2 ELECTRONS in the valence shell and similar CHEMICAL properties.

Discussion

3368.	State one reason for placing Mg and Ca in the same group of Periodic Table.
Answer» Solution :Both MG and CA contain TWO electrons in the OUTERMOST shell.

Discussion

3369.	State one difference between physical and chemical change.
Answer» Solution :Physical CHANGE - no new substance is formed, generally reversible e.g. : Melting of ice. CHEMICAL change - a new substance is formed, generally IRREVERSIBLE. e.g. : Electrolysis of WATER.

Discussion

3370.	State one basic difference between a physical change and a chemical change.
Answer» SOLUTION :In a PHYSICAL CHANGE, no new SUBSTANCE is formed INA chemical change, new substance is formed .

Discussion

3371.	State Ohm's law.
Answer» Solution :Under similar physical conditions and at constant temperature the current flowing thought a WIRE is directly PROPORTIONAL to the potential DIFFERENCE applied ACROSS its ends.

Discussion

3372.	State Newlands' Law of Octaves.
Answer» Solution : Newlands. LAW of Octaves states that “when ELEMENTS are arranged in order of increasing atomicweights, then every eighth element has PROPERTIES SIMILAR to that of the first element.”

Discussion

3373.	State modern periodic law of classification of elements.
Answer» SOLUTION :It states "Properties of ELEMENTS are periodic FUNCTION of their atomic number."

Discussion

3374.	Explain law of octaves.
Answer» Solution :“Any given ELEMENT will exhibit analogus BEHAVIOUR to the EIGHT element FOLLOWINGIT INTHE table”.This means everyeight element has the similar chemical and physical properties.

Discussion

3375.	State modern periodic law.
Answer» Solution : Modern PERIODIC LAW states that THEE physical and chemical PROPERTIES of element are the periodic function of their atomic NUMBERS.

Discussion

3376.	State Mendeleev's periodic law. Write two achievements of Mendeleev's periodic table.
Answer» Solution :Mendeleev.s PERIODIC Law : "PROPERTIES of elements are the periodic function of their ATOMIC masses." Achievements : (i) It could classify all the elements discovered at that time. (II) It helped in discovery of new elements. (iii) It helped in CORRECTION of atomic mass of some of the elements.

Discussion

3377.	State Mendeleev's law.
Answer» Solution :PROPERTIES of ELEMENTS are a PERIODIC function of ATOMIC MASS.

Discussion

3378.	State Joule's law of heating. Explain the workmg of electric filament bulb. OR State Ohm's law. How ammeter and voltmeter should be connected in electric circuit ? What is the use of these instruments, in the circuit ?
Answer» Solution :Joule.s Law: When CURRENT of I ampere flows in a wire of resistance R `Omega` for t seconds, the heat energy dissipated by it is given by H = `I^(2)`Rt (1) The filament of electric bulb must be MADE up of a substance so that it does not melt at very high temperature. (2) Tungsten with high melting point of 3380" is used for making bulb filaments. (3) The bulb is usually fiJJed with chemically INACTIVE NITROGEN and argon gases to prolong the life of filament. (4) The filament gets extermely hot and emits light. OR • Ohm.s Law : It states that "Physical conditions remaining same, the current flowing through a conductor is directly proportional to the potential difference across its two ENDS". i.e., V `alpha` I V = IR • Where the constant of proportionality R is called the electrical resistance or resistance of the conductor. • A voltmeter is connected in parallel with a device and an ammeter is connected in series. • Voltmeter is used to measure the voltage while ammeter is used to measure the current flowing in the circuit.

Discussion

3379.	State how the following conversions can be carried out: Ethyl chloride to ethyl alcohol.
Answer» SOLUTION :`C_2H_5Cl + KOH(AQ) (to) C_2H_5OH + KCL`

Discussion

3380.	State how the following conversions can be carried out: Ethyl alcohol to ethene.
Answer» SOLUTION :`C_2H_5OH OVERSET(conc.H_2SO_4)(to) C_2H_4 + H_2O`

Discussion

3381.	State how the following conversions can be carried out: Ethyl chloride to ethene.
Answer» SOLUTION :`C_2H_5Cl OVERSET("ALCOHOLIC KOH")(to) C_2H_4 + HCL`

Discussion

3382.	State how the following conversions can be carried out:Ethene to ethyl alcohol.
Answer» SOLUTION :`C_2H_4(g) + H_2O(g) OVERSET(H_3PO_4 "on SILICA , " 300^@" , 70 atm")(to) C_2H_5OH`

Discussion

3383.	State different forms of energy required for breaking down the molecules of reactant in decomposition reaction.
Answer» SOLUTION :HEAT, LIGHT and ELECTRICITY

Discussion

3384.	State Avogadro hypothesis (or) Avogadro's Law.
Answer» Solution :The Avogadro.s law states that ..EQUAL volume of all gases under similar conditions of temperature and PRESSURE CONTAIN equal number of MOLECULES... `[Vprop n]`

Discussion

3385.	State any two differencesbetween a strong electrolyte and a weak electrolyte .
Answer» SOLUTION :When elctric CURRENT is passed theorugh the two solutions separately , the intensity (brightness) of GLOW of the bulb is different .For stronger electrolyte , the bulb glows brighter . (i) In case of the solutions X, the bulb glows brightly .Therefore.solution X contains strong electrolyte .

Discussion

3386.	State any three physical properties of carbon compounds.
Answer» Solution :As CARBON compounds are covalent, the properties of covalent compounds are as FOLLOWS: a] They are soluble in non-polar organic solvents like ether, liquid benzene, etc., but insoluble in water. B] They have low MELTING points and low boiling points. c] They are bad conductors of heat and electricity.

Discussion

3387.	State and explain the applications of Avogadro's law.
Answer» Solution :Avogadro.s law : Equal volumes of all gases under the same conditions of temperature and pressure contain an equal number of molecules. Applications of Avogadro.s law : It is used to determine the atomicity of gases. It is helpful in determining the molecular formula of gaseous compounds. It establishes the relationship between the VAPOUR density and molecular MASS of a gas. It gives the value of molar value of molar VOLUME of gases at STP. Molar volume of a gas at STP = 22.4 litres. It explains GAY lussac.s law effectively.

Discussion

3388.	Stainless steel is made up of
Answer» `Fe , NI` and `C ` `Fe, Ni` and `Cr` `Fe , MN` and `Ni` NONE of these Answer :B

Discussion

3389.	Stainless steel contains
Answer» ANSWER :IRON, CARBON , CHROMIUM

Discussion

3390.	Stability of solid decreses in which of the following defects
Answer» Frenkel Schottky Both Stability is not AFFECTED by defect Answer :C

Discussion

3391.	Specific grabvity of 84% (w/w) pure HNO_(3) is 1.54. What volume of HNO_(3) is required to prepare one litre of 0.5 M HNO_(3) solutions?
Answer» Solution :Specific gravity of `HNO_(3) = 1.54` `M=w/"GMM"xx1000/V rArr0.5 = x/63 xx1000/1000 rArr x = 31.5`g `31.5" g of "NHO_(3)` is present in 1 L of solution. 84 g is present in 100 g of solution 31.5 g is present in ? g of solution ` = (31.5 xx 100)/84 = 37.5` g `"Density"="WEIGHT"//"VOLUME"rArr1.54 =37.5//"volume" rArr V = 37.5//1.54= 24.35` m L `V_(1)M_(1) = V_(2)M_(2)""24.35`m L of given` NHO_(3)` is required.

Discussion

3392.	Sometimes chlorine gas is passed through water for its purification. What will be the pH of such a sample of water?
Answer» EQUAL to 7 More than 7 Less than 7 Very NEAR to 8 Answer :C

Discussion

3393.	Some vinegar is dropped on solid sodium carbonate. Brisk efferevescence takes place with the evolutions of colourless gas. The gas is
Answer» CARBON monoxide hydrogen carbon dioxide oxygen ANSWER :C

Discussion

3394.	Some of the elements and their atomic numbers are mentioned in the following table : (i) How many valence electrons are there in the element 'R' ? (ii) What is the valency of 'P' ? (ii) Write the chemical formula of the compound formed by combining the elements ‘P' and 'Q'? (iv) Out of the two elements 'P' and 'S', which one is larger in size ?
Answer» SOLUTION :(i) 3. (II) 1. (iii) PQ. (iv) S.

Discussion

3395.	Some of the elements and their atomic numbers are given in the table. (i) How many valence electrons are there in the element R ? (ii) What is the valency of P? (iii) Write the chemical formula of the compound formed by combining the elements P and Q.
Answer» <P> Solution :(i) Electronic configuration of R is : `{:(K,L,M),(2,8,3):}` Thus, there are 3 valence electrons in R. (ii) Electronic configuration of P is : `{:(K,L),(2,1):}` Therefore, VALENCY of P is one. (III) P has one electron and Q has 7 electrons in the valence shell. Therefore, formula of the compound will be PQ.

Discussion

3396.	Some methods used for the laboratory preparation of salts are (a) metal + acid (b) carbonate + acid ( c) precipitation (double decomposition) (d) direct combination (e) titration Copy and complete the following table.
Answer» Solution :(i) - (E) (II) - ( c) (III) - (d) (IV) - (b) (v) - (a)

Discussion

3397.	Some metals react with water and produce metal oxides or hydroxides and liberated hydrogen gas. Metals like sodium and potassium react violently with cold water. However, calcium reacts less violently with cold water because it is less reactive as compared to Na and K. Magnesium does not react with cold water. It reacts with hot water to form magnesium hydroxide and hydrogen gas. Metals like aluminium, iron and zinc do not react with cold as well as hot water but they react with steam to form metal oxide and hydrogen gas. (i) Which gas is produced when reactive metal reacts with water ? (ii) How can we extinguish fire ? (iii) Why is sodium kept in kerosene oil ? (iv) Which metal did not react with water even in the presence of steam ? (v) How can we prevent iron from rust ?
Answer» Solution :(i) Hydrogen GAS. (ii) By carbon dioxide gas. (iii) Because SODIUM reacts violently with WATER and air. (iv) Lead, copper or gold (V) By painting IRON articles.

Discussion

3398.	Some metals like sodium can be cut with a knife. How do you explain with respect to metallic bond?
Answer» Solution :Sodium has one electron in its valence shell. Being the FIRST element of that period, it has large size. The force of attraction binding the metal ions with electrons, that means, metallic bond is weaker when COMPARED to the other METALS. Therefore, sodium is soft metal and can be CUT with a knife.

Discussion

3399.	Some groups of three elements are given below: Which of these groups is not an example of Dobereiner's triad ? Explain it.
Answer» SOLUTION :For group .A. : <BR> Average of ATOMIC masses of N and As `=(14+74.9)/(2)=44.45u` This average VALUE is not equal to the actual atomic mass of the middle ELEMENT phosphorus (P). Therefore, these three elements do not form a Dobereiner.s triad. For group .B. : Average of atomic masses of Ca and Ba `=(40.1+137.3)/(2)` =88.7u This average value is approximately equal to the atomic mass of the middle element strontium (Sr). Therefore, these three elements form a Dobereiner.s triad. For group .C. : Average of atomic masses of Cl and I `=(35.5+126.9)/(2)` =81.2u This average value is approximately equal to the mass of the middle element bromatomic ine (Br). Therefore, these three elements form a Dobereiner.s triad.

Discussion

3400.	Some esters are added to food items for special smells. An ester can be made from ethanol and ethanoic acid i] Name the ester obtained in the reaction that takes place in the presence of concentrated sulphuric acid. Write the chemical equation. ii] Name the process.
Answer» SOLUTION :i] Ethyle ethanoate `CH_3COOH + CH_2CH_3OH OVERSET("Con." H_2SO_4) UNDERSET("Ethyl ethanoate")(CH_3COOH_2CH_3)+ H_2O` . ii] This PROCESS is called ESTERFICATION.

Discussion

Explore topic-wise InterviewSolutions in .

State reasons for the following: Electric wires are covered with rubber like material.

Whichof the following metalscannot liberate hydrogen from dilutehydrochloric acid

State reason for the following statements : Tap water conducts electricity whereas distilled water does not

State reason for the following statements : For dilution of an acid, acid is added to water and not water to acid.

State reason for the following statements : During summer season, a milkman usually adds a very small amount of baking soda to fresh milk.

State reason for the following statements : Dry hydrogen chloride gas does not turn blue litmus red whereas hydrochloric acid does.

State reason for the following statements : Ammonia is a base but does not contain a hydroxyl group.

State reason for the following : Potato chips manufacturers usually flush bags of chips with nitrogen gas.

State reason for the following: (i) Lemon is used for restoring the shine of tarnished copper vessels. (ii) A metal sulphide is converted into its oxide to extract the metal from the sulphide ore. (iii) Copper wires are used in electrical connections.

State reason for the following : Iron articles loose their shine gradually.

State reason for the following : (i) Non-metals cannot displace hydrogen from the acids. (ii) Hydrogen is not a metal, yet it is placed in the activity series of metals. (iii) Aluminium is more reactive than iron, yet its corrosion is less than that of iron.

State reason for the following : Foods should be kept in air - tight containers.

State Periodic Law on which the Modern Periodic Table is based.

State Periodic Law on which the Modem Periodic Table is based.

State one use of anhydrous calcium chloride.

State three reasons for placing chlorine and bromine in the same group of the periodic table.

State one reason for placing Mg and Ca in the same group of Periodic Table.

State one difference between physical and chemical change.

State one basic difference between a physical change and a chemical change.

State Ohm's law.

State Newlands' Law of Octaves.

State modern periodic law of classification of elements.

Explain law of octaves.

State modern periodic law.

State Mendeleev's periodic law. Write two achievements of Mendeleev's periodic table.

State Mendeleev's law.

State Joule's law of heating. Explain the workmg of electric filament bulb. OR State Ohm's law. How ammeter and voltmeter should be connected in electric circuit ? What is the use of these instruments, in the circuit ?

State how the following conversions can be carried out: Ethyl chloride to ethyl alcohol.

State how the following conversions can be carried out: Ethyl alcohol to ethene.

State how the following conversions can be carried out: Ethyl chloride to ethene.

State how the following conversions can be carried out:Ethene to ethyl alcohol.

State different forms of energy required for breaking down the molecules of reactant in decomposition reaction.

State Avogadro hypothesis (or) Avogadro's Law.

State any two differencesbetween a strong electrolyte and a weak electrolyte .

State any three physical properties of carbon compounds.

State and explain the applications of Avogadro's law.

Stainless steel is made up of

Stainless steel contains

Stability of solid decreses in which of the following defects

Specific grabvity of 84% (w/w) pure HNO_(3) is 1.54. What volume of HNO_(3) is required to prepare one litre of 0.5 M HNO_(3) solutions?

Sometimes chlorine gas is passed through water for its purification. What will be the pH of such a sample of water?

Some vinegar is dropped on solid sodium carbonate. Brisk efferevescence takes place with the evolutions of colourless gas. The gas is

Some of the elements and their atomic numbers are given in the table. (i) How many valence electrons are there in the element R ? (ii) What is the valency of P? (iii) Write the chemical formula of the compound formed by combining the elements P and Q.

Some methods used for the laboratory preparation of salts are (a) metal + acid (b) carbonate + acid ( c) precipitation (double decomposition) (d) direct combination (e) titration Copy and complete the following table.

Some metals like sodium can be cut with a knife. How do you explain with respect to metallic bond?

Some groups of three elements are given below: Which of these groups is not an example of Dobereiner's triad ? Explain it.

Some esters are added to food items for special smells. An ester can be made from ethanol and ethanoic acid i] Name the ester obtained in the reaction that takes place in the presence of concentrated sulphuric acid. Write the chemical equation. ii] Name the process.