2599 + Interview Questions in Chemistry in Class 9 Page 31 InterviewSolution

1501.	Hydrogen and oxygen combine in the ratio of 1.8 by mass to form water , What mass of oxygen as would be required to react completely with 3 g of hydrogen gas .
Answer» Solution :It is given that the ratio of hydrogen and oxygen by mass to form WATER is 1:8. Then the mass of oxygen gas required to REACT COMPLETELY with lg of hydrogen gas is 8G. THEREFORE, the mass of oxygen gas required to react completely with 3 g of hydrogen gas is 8x3g=24 g.

Discussion

1502.	Hydrogen (""_(1)^(1)H) are isobars.
Answer» ANSWER :F

Discussion

1503.	How would youconfirmthat acolourlessLiquidgivento youis purewater?
Answer» SOLUTION :BOILING pointis thesuresttest to checkthe purity .If waterboilsarbitary`100^(@)C `, thenit is pure .

Discussion

1504.	How would you confirm that a colourless liquid given to you is pure water ?
Answer» Solution :TAKE a sample of colourless liquid and put on stove if it starts boiling exactly at `100^(@)C` then it is pure water. Any other colourless LIQUIED such as vinegar always have different boiling point . Also observe carefully that after some time whole liquid will CONVERT into vapour WITHOUT leaving any resideu.

Discussion

1505.	How will you show that cathode rays follows a straight path?
Answer»

Discussion

1506.	How will you separate the constituents present in the following mixtures ?(i) Common salt and water (ii) Iodine and sand (iii) Kerosene and water(iv) Sugar and sulphur.
Answer» Solution :(i) Common salt and water. Since common salt (sodium chloride) is soluble in water, it can be separated by crystallisation. The process of distillation can also be used because sodium chloride is non-volatile and water is volatile in nature. (ii) Iodine and sand. Sublimation process can be used. Iodine will sublime on HEATING while sand will remain unaffected. (iii) Kerosene and water. The liquids are not miscible with each other. Separation can be done by using a separating funnel. (iv) SUGAR and SULPHUR. The mixture is dissolved in carbon disulphide in a BEAKER by stirring with a glass rod. Sulphur dissolves while sugar remains as such. On filtering, sugar separates as the residue. The filtrate UPON concentration and cooling gives crystals of sulphur.

Discussion

1507.	How will you separate sulphur dioxide gas from the gaseous mixture of SO_2 and O_2 ?
Answer» Solution :`SO_2 ` gas from `O_2 ` can be separated by preferential LIQUEFACTION. `SO_2` gas liquefied under HIGH pressure and `O_2` is left behind. SINCE `SO_2` is ACIDIC in nature, it can also be separated by PASSING the gaseous mixture through KOH solution.

Discussion

1508.	How will you separate a mixture of salt, ammonium chloride and sand ? Write only the names of four methods used in proper order.
Answer» SOLUTION :SUBLIMATION, DECANTATION, FILTRATION, EVAPORATION.

Discussion

1509.	How will you separate a mixture of naphthalene balls powder and common salt ? Draw a neat and labelled diagram to show the process.
Answer» SOLUTION :The SEPARATION can be DONE by SUBLIMATION.

Discussion

1510.	How will you separate a mixture containing saw dust, naphthaleneand iron filings?
Answer» Solution :When a magnet is brought near the MIXTURE CONTAINING SAW dust naphthalene and iron filings it attracts the iron filings. Thus iron filings are separated. The mixture of naphthalene and saw dust are put in a china dish and covered with a perforated abestos sheet An inverted funnel is PLACED over the asbestos sheet. The open end of the stem of the funnel is closed, using cotton wool. The china dish is heated The pure vapour of naphthalene solid pass through the holes in the asbestos sheet and CONDENSE on the inner side of the funnel The saw dust is left in the china dish.

Discussion

1511.	How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25^(@)C), which are miscible with each other ?
Answer» Solution :KEROSENE and petrol do not decompose on HEATING. The difference in their boiling points is sufficiently apart. Hence the mixture of kerosene and petrol can be separated by distillation. Procedure : Take the mixture of kerosene and petrol in a distillation flask. Fit it with a thermometer. Arrange the apparatus as shown in the figure. HEAT the mixture slowly. KEEP a close watchat the thermometer. At a certain point, the temperature remains steady. The boiling point of petrol is lower than that of kerosene. Petrol vapourises first and is collected in beaker. Kerosene is left behind in the distillation flask.

Discussion

1512.	How will you separate a mixture contaning kerosene and petrol ( differencein their boiling point of More than 25 C ) which are miscible with each other ?
Answer» Solution :Kerosene and petrol are miscible liquids also the difference between this BOILING point is more than `25^(@)C` so they can be SEPARATED by the method of distillation. In this method, the mixture of kerosene and petrol is taken in a distillation flask with a thermometer fitted in it. We also need a beaker, a water condenser, and a Bunsen burner. The apparatus is arranged as shown in the above figure. Then, the mixure is heaed slowly. The thermometer should be watched simultaneously. Kerosense will VAPORIZE and CONDENSE in the water condenser. The condensed kerosene is collected from the condenser outlet, where as petrol is left BEHIND in the distillation flask.

Discussion

1513.	How will you separate a mixture containing kerosene and petrol (difference in their boiling point is less than 25 K) which are miscible with each other ? Explain.
Answer» Solution :Both are miscible liquids. SINCE the difference in the boiling points is LESS than 25 K, the separation can be done with the help of fractional distillation technique. Petrol with less boiling point DISTILS FIRST leaving behind kerosene in the distillation from flask. However, it is very difficult to APPLY this technique since both are highly flammable liquids and a great deal of precaution is needed. For the details of fractional distillation.

Discussion

1514.	How will you find the valency of chlorine, sulphur and magnesium ?
Answer» Solution :If the number of electrons in the OUTERMOST shell of the atom of an element is less than or EQUAL to 4 then the valency of the element is equal to the number of electrons in the outermost, shell on the other hand, if the number of electrons in the outermost shell of the atom of an element is greater than 4, then the valency of that element is determined and SUBTRACTING the number of electrons in the outermost shell from 8.The distribution electrons in chlorine, sulphur and magnesium atoms are 2,8,7,2,8,6 and 2,8,2 respectively. `therefore` The number of electrons in the outermost shell of chlorine, sulphur and magnesium atoms are 7,6 and 2 respectively. ● THUS the valency of chlorine `= 8-7=1` ● The valency of sulphur `= 8-6=2` ● The valency of magnesium = 2

Discussion

1515.	How will you find the valency of chlorine, sulphur and magensium ?
Answer» SOLUTION :VALENCY is the combining capacity of an atom of an element. The number ofprotons = number of electrons. Chlorine : Atomic number 17 `THEREFORE` number of protons = 17 Number of electrons = 17 `therefore` distribution of electrons : K SHELL: 2: L shell: 8 and M shell: 7. The outermost orbit of chlorine contains 7 electrons. So, chlorine atom will gain 1 electron to complete OCTET in the outermost shell. `therefore` the valency of chlorine atom is 1. `therefore` number of protons = 16 number of electrons = 16 `therefore` distribution of electrons : K shell : 2 : L shell :8 and M shell : 6 The outermost orbit of sulphur contains 6 electrons. So, magnesium atom would donate 2 electrons and complete octet in the outermost shell. `therefore ` the valency of magnesium is 2. Note: (1 ) If the atom galns electron to complete outermost shell, its valency is considered negative.

Discussion

1516.	How will you confirm that a colourless liquid given to you is pure water ?
Answer» Solution :A pure LIQUID has a definite boiling POINT at 1 atmospheric pressure. If the given colourless liquid boils at `100^(@)C` (373 K) at 1 atmospheric pressure, then it is pure water, otherwise not.

Discussion

1517.	How will you change water from gaseous state to liquid state ? Suggest a simple activity.
Answer» Solution :Pass the water VAPOURS or steam through a water CONDENSER as USED in case of simple distrillation )For details, consult next chapter). It gets condensed to form LIQUID water.

Discussion

1518.	How were cathode rays discovered by Thomson? Describe with the help of an experiment.
Answer»

Discussion

1519.	How the ions are formed?
Answer» ANSWER :Atom BECOMES charged when there is TRANSFER of electrons [LOSE or gain electrons] they are called ions.

Discussion

1520.	How nitric acid reacts with sulphur ?
Answer» SOLUTION :N/A

Discussion

1521.	How much water should be added to 12 ml alcohol so the concentration of solution 3 becomes 12% ?
Answer» Solution :VOLUME of solute = 12 ML Volume of SOLVENT = x mL Volume of solution = (12 + x) mL Volume percentage of solution = `("Volume of solute")/("Volume of solution")xx100` `12=12/(x+12)xx100` `(12(x+12))/12=100` `x+12=100` x = 88 mL

Discussion

1522.	How many periods in the modern periodic table?
Answer» ANSWER :7

Discussion

1523.	(a) How many particles are represented by 0.25 mole of an element? (b)Out of 4g of methane and 11 g of CO_2 , Does they contain equal no. of molecules (1 N _A=6.022xx10^(23) molecules )
Answer» SOLUTION :1.0mole of the element represents particles `=6.022xx10^(23)` 0.25mole of the elements represents particles =`=((6.022xx10^23)xx(0.25"MOL"))/((1.0"mol"))` `=1.505xx10^(23)"particles"` (b) 4g of METHANE `(CH_(4))` represebts moles `=((1"mol")xx(4g))/((16g))=0.25"mol"` `11"g of "CO_(2)"represents moles"=((1"mol")xx(11g))/((44g))=0.25"mol"` Since both `CH_(4) and CO_(2)` haave same number of moles (0.25moles), they have also same number of molecules.

Discussion

1524.	How many pairs of electrons are shared?
Answer» ANSWER :ONE PAIR

Discussion

1525.	How many natural physical states of matter are there?
Answer» Two Three Four Five

Discussion

1526.	How many moles of Cr are there in 85 g of Cr_(2) S_(3)? (Cr = 52 , S = 32 )
Answer» Solution :Molecular mass of `Cr_(2)S_(3) = 2 xx 52 + 3 xx 32 = 104 + 96 = 200` 200 g of `Cr_(2)S_(3)` contains 104 g of Cr. `THEREFORE` 85 g of `Cr_(2)S_(3)` contains `(104 xx 85)/(200) "" g` of Cr = 44.2 g THUS , NUMBER of moles of Cr = `(44.2)/(52) = 0.85` .

Discussion

1527.	How many moles are there in 5 g of calcium ?
Answer» SOLUTION :`0.125` MOL

Discussion

1528.	How many moles are present in 11.5 g of sodium ?
Answer» Solution :Gram atomic mass of SODIUM = 23 g 23 g of sodium represent = 1 mole `THEREFORE 115` g of sodium represent `= ("(1 mol )" xx 11 5)/(230 g) = 0.5` mol `6.022` atoms of element will have mass = `2xx 10^(-23) g xx 6022 xx 10^(23)` `= 12044 g = 12 0` gram

Discussion

1529.	How many molcs of nitrogen atoms are there in 28 g nitrogen gas?
Answer» 1 2 2.3 5 Solution :Mole= `("given mass")/("MOLECULAR mass")=(28)/(28) = 1` 1 mole `N_(2)` ATOMS `:.` Atoms of nitrogen = 2 mole

Discussion

1530.	How many hours or days does it take forthe colour of ink to spread evenly throughtout the water?
Answer» Solution :The colour of INK spreads EVENLY throughtout the WATER WITHIN few minutes.

Discussion

1531.	How many grams of sodium wil have the same number of atoms as 6 grams of magnesium ("Given Na"=23u, Mg=24u)?
Answer» Solution :Number of grams- atoms of MG = `("MASS of Mg in atoms")/("gram-atomic mass") = (6g)/(24 G) = (1)/(4)` `THEREFORE` gram - atoms of sodium should be `(1)/(4)` `because`1 gram - atom of sodium = 23 g `therefore (1)/(4)` gram-atom of sodium = `23 xx 1/4 g = 5.75 g` .

Discussion

1532.	How many grams of potassium will have the same number of atoms as 6 grams of sodium ? (Atomic mass of Na = 23, K = 39)
Answer» Solution :Number of SODIUM atoms `= ("given mass")/("molar mass") xx "Avogadro number"` `=(6)/(23) xx 6.022 xx 10^(23) ~~ 1.57 xx 10^(23)` Number of potassium atoms present in 39 g = `6.022 xx 10^(23)` `:.` 1 ATOM of K is present in`(39)/(6.023 xx 10^(23))` `:. 1.57 xx 10^(23)` atoms of K are present in `(39 xx 1.57 xx 10^(23))/(6.022 xx 10^(23)) g ~~ 10.17 g` 10.17 g of potassium.

Discussion

1533.	How many grams of potassium chloride is present in 250 g of saturated solution ? The solubility of KCl is 35.8 at 25^(@)C ?
Answer» Solution :Solubility` = ("Mass of solute")/("Mass of solvent") XX 100` `35.8 = (X)/(250 -x) xx 100` `(250 - x)35.8 = 100 x rArr 8950 - 35.8 x = 100x rArr x = 65.9 G`

Discussion

1534.	How many grams of each of the following elements must be taken to get 1 mol of the element ? (a) Sodium (b) Chlorine (C ) Copper
Answer» Solution :The mass of 1 MOL of an element is its atomic mass EXPRESSED in grams . SINCE the atomic masses of sodium , chlorine and copper are 23 g , 35.5 g and 63.5 g respectively , we get (a) 23 g (b) 35.5 g(c) 63.5 g

Discussion

1535.	How many gram molecules of H_(2)SO_(4), are present in 4.9 g of the acid? (b) How many atoms of hydrogen and oxygen are present in 0-15 mole of water (H_(2)O)?
Answer» Solution :(a) GRAM molecular mass of `H_(2)SO_(4)=2xx1+32+4xx16=98g` `98g of H_(2)SO_(4)=1"gram molecules"` `4.9"g of "H_(2)SO_(4)=(4.9)/(98)=0.05"gram molecule"` (B) `underset("1mol")(H_(2)O) =underset("2 gram aroms")(2H)+underset(1"grams atom")(O)` 1 MOLE of water `(H_(2)O)` has H atoms=2grams 0.15 MOLES of water `(H_(2)O)` has H atoms=`(2xx0.15)=0.30grams` `=0.30xx6.022xx10^(23)"atoms"` `=1.81xx10^(23)"atoms"` 1 mole of water `(H_(2)O)` has O atoms =1 gram atoms 0.015 moles of water `(H_(2)O)` has O atoms=0.15gram atoms `=0.15xx6.022xx10^(23)=9.03xx10^(23)"atoms"`

Discussion

1536.	How many electrons can be accommodated in the outermost orbit of an element ?
Answer» 2 8 18 16

Discussion

1537.	How many electrons are there in the outermost shell of each element?
Answer» ANSWER :8

Discussion

1538.	How many electrons are accepted by oxygen?
Answer» ANSWER :2

Discussion

1539.	How many electron pairs are shared?
Answer» ANSWER :ONE PAIR of ELECTRONS

Discussion

1540.	How many atoms of oxygen are present in 50 g of CaCO_(3)
Answer» Solution :Molecular MASS of `CaCO_(3)=40+12+3x 16` `=100g` Atoms of oxygen present in 100g of `CaCO=3x 6.022x10^(23)` atoms. Atoms of oxygen present in 50G of `CaCo` `={(3x6.022xx10^(23))//100}xx50` atoms `=9.033x 10^(23)`

Discussion

1541.	How many atoms of copper are present in 0.35 mol of pure copper metal ?
Answer» Solution :1 MOL of COPPER metal = `6.022 xx 10^(23)` atoms of CU . `therefore` 0.35 mol of copper metal = `0.35 xx 6.022 xx 10^(23)` atoms of Cu = `2.1 xx 10^(23)` atoms of Cu .

Discussion

1542.	How many atoms are there in 100 amu of helium , if atomic mass of helium is 4 amu ?
Answer» Solution :Number of He ATOMS = `("MASS of HELIUM")/("mass of 1 ATOM of helium") = (100 "amu")/(4 "amu") = 25` .

Discussion

1543.	How many atoms are present in (i) H_(2)S molecule and (ii) PO_(4)^(3-) ion ?
Answer» Solution :(i) In `H_(2)S` molecule there are 3 atoms. (2 of hydrogen and 1 of sulphur.) (ii) In `PO_(2)^(3-)` ION there are 5 atoms. (1 atom of PHOSPHORUS and 1 atoms of OXYGEN.)

Discussion

1544.	How many atoms are present in phosphate ion ?
Answer» SOLUTION :PHOSPHATE ION is `PO_(4)^(3-)`. The number of atoms in it is 5 (1 + 4).

Discussion

1545.	How many atoms are present in a (ii) PO_(4)^(3-) ion ?
Answer» <P> SOLUTION :`P to 1 ` ATOM `O to 4 ` atom

Discussion

1546.	How many atoms are present in a (i) H_(2)S molecules ?
Answer» Solution :(i)In an `H_(2)S` molecule THREE atoms are present two of hydrogen and one of SULPHUR. (II) In a `Po_(4)` inon, five atoms are present, one of phosphorous and four of oxygen.

Discussion

1547.	How is valency and electron transfer related in this case?
Answer» ANSWER :Same

Discussion

1548.	"How is the principle of regelation applicable for welding?" Explain.
Answer» Solution :(i) process ofwelding (II) Changes inpressure duringthe process (iii) EFFECT of change inpressure on MELTINGPOINT

Discussion

1549.	The diagram shows an experimental set up for the laboratory preparation of a pungent smelling gas. The gas is alkaline in nature. How is the gas being collected ?
Answer» Solution :Passing the gas through, solution of silver nitrate, lead nitrate and KOH solution. The gas is COLLECTED by the DOWNWARD displacement of WATER.

Discussion

1550.	How is the high compressibility of gases useful to us?
Answer» Solution :Petroleum gases are COMPRESSED and stored as a LIQUID (Liquefied Petroleum Gas). Oxygen gas is compressed and supplied to hospitals in CYLINDERS. CNG (Compressed Natural Gas) is USED as fuel to vehicles.

Discussion

Explore topic-wise InterviewSolutions in .

Hydrogen and oxygen combine in the ratio of 1.8 by mass to form water , What mass of oxygen as would be required to react completely with 3 g of hydrogen gas .

Hydrogen (""_(1)^(1)H) are isobars.

How would youconfirmthat acolourlessLiquidgivento youis purewater?

How would you confirm that a colourless liquid given to you is pure water ?

How will you show that cathode rays follows a straight path?

How will you separate the constituents present in the following mixtures ?(i) Common salt and water (ii) Iodine and sand (iii) Kerosene and water(iv) Sugar and sulphur.

How will you separate sulphur dioxide gas from the gaseous mixture of SO_2 and O_2 ?

How will you separate a mixture of salt, ammonium chloride and sand ? Write only the names of four methods used in proper order.

How will you separate a mixture of naphthalene balls powder and common salt ? Draw a neat and labelled diagram to show the process.

How will you separate a mixture containing saw dust, naphthaleneand iron filings?

How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25^(@)C), which are miscible with each other ?

How will you separate a mixture contaning kerosene and petrol ( differencein their boiling point of More than 25 C ) which are miscible with each other ?

How will you separate a mixture containing kerosene and petrol (difference in their boiling point is less than 25 K) which are miscible with each other ? Explain.

How will you find the valency of chlorine, sulphur and magnesium ?

How will you find the valency of chlorine, sulphur and magensium ?

How will you confirm that a colourless liquid given to you is pure water ?

How will you change water from gaseous state to liquid state ? Suggest a simple activity.

How were cathode rays discovered by Thomson? Describe with the help of an experiment.

How the ions are formed?

How nitric acid reacts with sulphur ?

How much water should be added to 12 ml alcohol so the concentration of solution 3 becomes 12% ?

How many periods in the modern periodic table?

(a) How many particles are represented by 0.25 mole of an element? (b)Out of 4g of methane and 11 g of CO_2 , Does they contain equal no. of molecules (1 N _A=6.022xx10^(23) molecules )

How many pairs of electrons are shared?

How many natural physical states of matter are there?

How many moles of Cr are there in 85 g of Cr_(2) S_(3)? (Cr = 52 , S = 32 )

How many moles are there in 5 g of calcium ?

How many moles are present in 11.5 g of sodium ?

How many molcs of nitrogen atoms are there in 28 g nitrogen gas?

How many hours or days does it take forthe colour of ink to spread evenly throughtout the water?

How many grams of sodium wil have the same number of atoms as 6 grams of magnesium ("Given Na"=23u, Mg=24u)?

How many grams of potassium will have the same number of atoms as 6 grams of sodium ? (Atomic mass of Na = 23, K = 39)

How many grams of potassium chloride is present in 250 g of saturated solution ? The solubility of KCl is 35.8 at 25^(@)C ?

How many grams of each of the following elements must be taken to get 1 mol of the element ? (a) Sodium (b) Chlorine (C ) Copper

How many gram molecules of H_(2)SO_(4), are present in 4.9 g of the acid? (b) How many atoms of hydrogen and oxygen are present in 0-15 mole of water (H_(2)O)?

How many electrons can be accommodated in the outermost orbit of an element ?

How many electrons are there in the outermost shell of each element?

How many electrons are accepted by oxygen?

How many electron pairs are shared?

How many atoms of oxygen are present in 50 g of CaCO_(3)

How many atoms of copper are present in 0.35 mol of pure copper metal ?

How many atoms are there in 100 amu of helium , if atomic mass of helium is 4 amu ?

How many atoms are present in (i) H_(2)S molecule and (ii) PO_(4)^(3-) ion ?

How many atoms are present in phosphate ion ?

How many atoms are present in a (ii) PO_(4)^(3-) ion ?

How many atoms are present in a (i) H_(2)S molecules ?

How is valency and electron transfer related in this case?

"How is the principle of regelation applicable for welding?" Explain.

The diagram shows an experimental set up for the laboratory preparation of a pungent smelling gas. The gas is alkaline in nature. How is the gas being collected ?

How is the high compressibility of gases useful to us?