Atoms and Molecules
Multiple Choice Questions
1. Which of the following correctly represents
(i) 2 moles of
(ii) 20 moles of water
(iii)
(iv)
(a) (i)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)
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Answer
Answer is (d) (ii) and (iv)
Explanation:
Number of moles
Number of moles
Number of moles
Number of molecules
Thus, option (d) is correct.
(a) Atoms are not able to exist independently
(b) Atoms are the basic units from which molecules and ions are formed
(c) Atoms are always neutral in nature
(d) Atoms aggregate in large numbers to form the matter that we can see, feel or touch
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Answer
Answer is (d) Atoms aggregate in large numbers to form the matter that we can see, feel or touch
Explanation:
Atoms aggregate in large numbers to form the matter But we cannot see the matter with our naked eyes.
(a)
(b)
(c)
(d)
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Answer
Answer is (b)
Explanation:
Chemical formula of Nitrogen is
(a) So
(b) Sd
(c) NA
(d)
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Answer
Answer is (d)
Explanation:
Sodium word is derived from Latin word Natrium hence the chemical name of sodium is Na.
(a) 0.2 mole of sucrose (
(b) 2 moles of
(c) 2 moles of
(d) 10 moles of
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Answer
Answer is (c) 2 moles of
Explanation:
Weight of a sample in grant
(a) 0.2 moles of
(b) 2 moles of
(c) 2 moles of CaCO? 2 x IIMI -
Hence, option (c) is correct.
(a)
(b)
(c)
(d)
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Answer
Answer is (d)
Explanation:
Number of atoms
(a)
(b)
(c)
(d)
Note:
(a)
(b)
(c)
(d)
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Answer
Answer is (c)
Note: NA
Explanation:
(a)
(b)
(c)
(d)
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Answer
Answer is (a) 2316 g
Explanation:
Mass of one atom of oxygen
Note:
(a)
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Answer
Answer is (a)
Explanation:
1 mol of sucrose
Total number of oxygen atoms
Number of oxygen atoms from sucrose + Number of oxygen atoms from water
Number of oxygen atoms in solution
(a) only when energy is given to the system
(b) only when energy is taken out from the system
(c) when energy is either given to, or taken out from the system
(d) without any energy change
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Answer
Answer is (c) when energy is either given to, or taken out from the system
Short Answer Questions
(a)
(b) BiPO4
(c)
(d)
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Answer
Answer is (b) BiPO4, Its name is Bismuth Phosphate
Explanation:
Bismuth phosphate is right because Both ions are trivalent Bismuth phosphate(Bi3+- Trivalent anion. anion is an ion that is negatively charged).
(a) Copper (II) bromide
(b) Aluminium (III) nitrate
(c) Calcium (II) phosphate
(d) Iron (III) sulphide
(e) Mercury (II) chloride
(f) Magnesium (II) acetate
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Answer
Answers are
(a) Copper (II) bromide- CuBr2
(b) Aluminium (III) nitrate
(c) Calcium (II) phosphate - Ca3(PO4)2
(d) Iron (III) sulphide - Fe2S3
(e) Mercury (II) chloride -
(f) Magnesium (II) acetate-
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Answer
Answers are
(a)
b)
(c)
(d)
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a) In
b) In
c) In
d) In
(a) Calcium and fluorine
(b) Hydrogen and sulphur
(c) Nitrogen and hydrogen
(d) Carbon and chlorine
(e) Sodium and oxygen
(f) Carbon and oxygen
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Answer
(b) Hydrogen and sulphur-
(c) Nitrogen and hydrogen-
(d) Carbon and chlorine
(e) Sodium and oxygen -
(f) Carbon and oxygen-
(a) Cobalt
(b) Carbon c
(c) Aluminium AL
(d) Helium He
(e) Sodium So
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Answer
Cobalt CO is wrong, correct symbol is Co
Carbon c is wrong, correct symbol is
Alluminium AL is wrong, correct symbol is
Helium He is the right symbol
Sodium So is wrong, correct symbol is
(a) Ammonia
(b) Carbon monoxide
(c) Hydrogen chloride
(d) Aluminium fluoride
(e) Magnesium sulphide
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Answer
Sl. No. | Compounds | Chemical formula | Ratio by mass of the combining elements |
---|---|---|---|
(a) | Ammonia | ||
(b) | Carbon monoxide | ||
(c) | Aluminium fluoride | ||
(d) | Aluminium fluoride | ||
(e) | Magnesium sulphide |
(a)
(b)
(c)
(d)
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Answer
(a)
(b)
(c)
(d)
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Answer
Mass of 1 mole of a substance is equal to its relative atomic or molecular mass in grams.
Mass of one mole (Avogadro Number) of neutrons
Mass of one neutron
Mass of one molecule of water
Mass of one molecule of water
Avogadro number
There are 8 neutrons in one atom of oxygen
Number of neutrons in oxygen= number of oxygen - Atomic number of oxygen
Oxygen’s atomic weight
increases with an increase in temperature.
Therefore the mass is 16
Therefore number of neutrons
Mass of one neutron
Mass of 8 neutrons
Fraction of mass of water due to neutrons
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Solubility is the ability of a solute to get dissolved in
Ex: Sugar dissolves faster in hot water than in cold water.
(a) F2
(b) NO2
(c) N2O
(d)
(e)
(f)
(g) P4010
(H)
(i)
(j)
(k)
(l)
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Answer
a) Monoatomic are inert gases that do not combine and exist as monoatomic gases
b) Diatomic- (a) 2 - diatomic-
c) Triatomic-N2O
d) Tetraatomic-
e) Octa atomic-
f) Polyatomic.
To examine if the fine white coloured powder is sugar pr salt we can conduct two experiments.
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Answer
1. Heating: Upon heating sugar melts to liquid form because sucrose has a decomposition point and melting point at temperatures between 190 to 192 degrees Celsius. This will turn sugar to light brown colour. Upon heat further sugar gets charred to black colour.
Salt has a melting point of 841 degrees Celsius and 1545.8 degrees Fahrenheit. If we don’t heat it to that point nothing change is observed.
2. Electric conductivity:
If we dissolve the given substance in water we can check for electric conductivity to check whether the substance is sugar or salt. If it is salt it conducts electricity. Because salt
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Answer
Number of moles
atomic weight
Long Answer Questions
24. Verify by calculating that (a) 5 moles of
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Answer
(a) Molar mass of CO2
5 moles of CO2 have mass
Similarly, molar mass of
5 moles of
It is verified that 5 moles of
(b) Number of moles
Atomic weight of
Number of moles in
Number of moles in
Atomic weight of
Ratio 6:10
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Answer
a)
Ca:
40:
(b)
24:
24: 71
(c)
2:
1:
(d)
14: 3
(f)
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1 mole of calcium chloride
Therefore
Since 1 formula unit
therefore,
No. of ions
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Sodium atom and ion differ by one electron. For 100 moles each of sodium atoms and ions there would be a difference of 100 moles of electrons.
Mass of 100 moles of electrons
Mass of 1 mole of electron
Mass of one electron
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Molar mass of
1 molecule of
Therefore, Mass of
232.6
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One mole of screws weigh
Mass of the Earth / Mass of 1 mole of screws
$ 2. 475 \times 10^{21} $
Mass of earth is
The earth is 2400 times heavier than one mole of screws
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We know,
1 mole
The number of moles
Avogadro Number
(a) Whose container is heavier?
(b) Whose container has more number of atoms?
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Answer
a) Mass of sodium atoms carried by Krish
Atomic weight of
While mass of carbon atom carried by Raunak
b) Thus, Krish’s container has more number of atoms
Species property |
||||
---|---|---|---|---|
No of Moles | 2 | - | - | 0.5 |
No of particles | - | - | 0 | |
Mass | - | 0 |
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Species property | ||||
---|---|---|---|---|
No of Moles | 2 | 0.5 | 5 | 0.5 |
No of particles | ||||
Mass |
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Number of moles of stars
(a) 103
(b) 10-1
(c) 10-2
(d) 10-6
(e) 10-9
(f) 10-12
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Answer
a)
(b)
(c)
(d)
(e)
(f)
(a)
(b)
(c)
(d)
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(a)
(b)
(c)
(d)
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Mg2+ ion and Mg atom differ by two electrons.
103 moles of Mg2+ and Mg atoms would differ by
Mass of
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No. of moles of atoms
For
Number of molecules
Molar mass of
Molar mass of
Number of molecules
No. of atoms
For
100/17 moles
Number of molecules
No. of atoms in
Therefore,
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Answer
therefore
Hence,
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Answer
One gram of gold sample will contain
Number of moles of gold=mass of gold
atomic mass of gold
One mole of gold contains NA atoms
Therefore, 0.0046 mole of gold will contain
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Answer
While forming some compounds, atoms gain or lose electrons, and form electrically charged particles called ions. Compounds that are formed by the attraction of cations and anions are called as ionic compounds.
Ex. 2
Sodium is a group 1 metal, thus forms a +1 charged cation. Chlorine is a non-metal, and has the ability to form a 1 charged anion.
Compounds formed due to bonding of uncharged ions are called as molecular compounds and the bonding between them is called covalent bonding. Molecular compounds are formed by sharing of electrons between the two atoms and the elements are held together by covalent bonds.
Ex:
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Answer
Mass of one mole of Aluminium atom
We know, if atoms convert into ions, only transfer of electrons takes place, in
So,
Mass of
Now,
You see mass of aluminium atom is greater than aluminium ion by 3 electrons
Difference in mass
Compute the ratio of the number of atoms of gold and silver in the ornament.
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Mass of silver
Mass of gold
Number of atoms of silver
Ratio of number of atoms of gold to silver
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Hence
Molar mass of Methane
Mass of methane
Ethane
If
So
(a) In a chemical reaction, the sum of the masses of the reactants and products remains unchanged. This is called
(b) A group of atoms carrying a fixed charge on them is called
(c) The formula unit mass of
(d) Formula of sodium carbonate is
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Answer
Answers
a) Law of conservation of mass
b) Ions c) 310
Explanation :
Across | Down |
---|---|
The element used by Rutherford during his |
A white lustrous metal used for making ornaments and which tends to get tarnished black in the presence of moist air |
An element which forms rust on exposure to moist air |
Both brass and bronze are alloys of the element |
A very reactive non-metal stored under water |
The metal which exists in the liquid state at room temperature |
Zinc metal when treated with dilute hydrochloric acid produces a gas of this element which when tested with burning splinter produces a pop sound. |
An element with symbol |
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(a)
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b) Six : Helium (He); Neon ( Ne); Argon (Ar); Krypton (Kr); Xenon (Xe); Radon (Rn).
(a) Caustic potash
(b) Baking powder
(c) Lime stone
(d) Caustic soda
(e) Ethanol
(f) Common salt
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The formulae for the following and calculate the molecular mass for each one of them.
Sl No | Compound | Formula | Molecular mass |
---|---|---|---|
A | Caustic Potash | ||
B | Baking powder | ||
C | Lime stone | ||
D | Caustic soda | ||
E | Ethanol | ||
F | Common Salt |
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Answer
1 mole of glucose needs 6 moles of water
Volume of water used