CBSE Questions for Class 9 Chemistry Atoms And Molecules Quiz 10 - MCQExams.com

Which of the following statements is incorrect?
  • One gram atom of carbon contains Avogadro's number of atoms.
  • One mole of oxygen gas contains Avogadro's number of molecules.
  • One mole of hydrogen gas contains Avogadro's number of atoms.
  • One mole of electrons stands for $$6.02\times{10}^{23}$$ electrons.
What mass of sodium chloride will react with 34.0 g of silver nitrate to produce 17 g of sodium nitrate and 28.70 g of silver chloride if the law of conservation of mass holds good ?
  • 12.35 grams
  • 11.70 grams
  • 9.32 grams
  • None of these
A compound contains $$10^{-2}\%$$ of phosphorus. If the atomic mass of P is $$31$$, then the molecular mass of the compound having one phosphorous atom per molecule is:
  • $$3.1\times 10^5$$
  • $$3.1$$
  • $$31$$
  • None of these
The Avogadro number ($$N_A$$), is changed from $$6.022\times 10^{23}$$ $$mol^{-1}$$ to $$6.022\times 10^{20}$$ $$mol^{-1}$$, this would change:
  • the ratio of chemical species to each other in a balanced equation
  • the ratio of elements to each other in a compound
  • the definition of mass in units of grams
  • the mass of one mole of carbon
The number of molecule in $$4.25$$g of $$NH_3$$ is:
  • $$1.505\times 10^{23}$$
  • $$3.01\times 10^{23}$$
  • $$6.02\times 10^{23}$$
  • none of these
A sample of potato starch was ground in a ball mill to give a starch-like molecule of lower molecular weight. The product analysed was 0.086 % phosphorus. If each molecule is assumed to contain one atom of phosphorus, what is the molecular mass of the material?
  • $$3.42\times 10^4$$ amu
  • $$3.72\times 10^4$$ amu
  • $$3.6\times 10^4$$ amu
  • None of these
A compound contains $$4$$% oxygen, then the minimum molecular weight of that compound will be:
  • $$400g$$
  • $$800g$$
  • $$200g$$
  • $$100g$$
A gaseous mixture contains oxygen and nitrogen in the ratio of 1: 8 by mass. Therefore, the ratio of their respective number of molecules is:
  • 1 : 8
  • 1 : 1
  • 7 : 64
  • 1 :2
Mass of one atom of $$X$$ is $$2.66\times 10^{-23}\ g$$, then its $$32\ g$$ contains mole equal to
  • $$32\times 2.66\times 10^{-23}\ mol$$
  • $$\dfrac{32}{2.66\times 10^{-23}\times 6.02\times 10^{23}}\ mol$$
  • $$\dfrac{32\times 2.66\times 10^{-23}}{6.02\times 10^{23}}\ mol$$
  • $$None\ of\ these$$
The number of atoms of oxygen present in 10.6 g of $$Na_2CO_3$$ will be:
  • $$6.02 \times 10^{22}$$
  • $$12.04 \times 10^{22}$$
  • $$1.806 \times 10^{23}$$
  • $$31.8$$
Which of the following is correct increasing order of molecular mass?
  • $${ H }_{ 2 }O<HCl<{ H }_{ 2 }S<{ CO }_{ 2 }$$
  • $$H_2O<H_2S<HCl<CO_2$$
  • $${ H }_{ 2 }O<CO_2<<HCl<{ H }_{ 2 }S$$
  • $$HCl<{ H }_{ 2 }S<{ H }_{ 2 }O<{ CO }_{ 2 }$$
Molecules consisting of more than three atoms are called polyatomic molecules.
  • True
  • False
Find number of oxygen atoms present in $$100 \ mg$$ of $$CaCO_3$$.
(Atomic Mass of $$Ca=40 \ u, \ C=12 \ u, \ O=16 \ $$)
  • $$6.02 \times 10^{23}$$
  • $$6.02 \times 10^{20}$$
  • $$1.806\times 10^{21}$$
  • $$1.204 \times 10^{20}$$
If $$x \ g$$ of an element $$A$$ contains $$\cfrac y{80}$$ atoms and $$2x \ g$$ of an element $$B$$ contains $$\cfrac y{40}$$ atoms then the ratio of atomic weights of two elements $$A$$ and $$B$$ is:
  • $$1:1$$
  • $$1:4$$
  • $$4:1$$
  • $$2:1$$
Which of the following has the highest mass? 
  • (a) $$50$$ gms of iron
  • (b) $$5$$ moles of nitrogen gas
  • (c) $$1$$ gm of atom
  • (d)$$ 5 \times 10^{23} $$ atoms of carbon
If the molecular mass of a compound is $$74.5$$ then the compound is:
  • $$LiCl$$
  • $$HCl$$
  • $$NaCl$$
  • $$KCl$$
A sample of $${ CaCO }_{ 3 }$$ has $$Ca=40$$%, $$C=12$$% and $$O=48$$%. If the law of constant proportion is true then the weight of calcium in $$5g$$ of a sample of $${ CaCO }_{ 3 }$$ from another source will be:
  • $$0.20g$$
  • $$2.0g$$
  • $$2.5g$$
  • $$4.0g$$
Total no. of atoms in $$44\ g$$ of $$CO_{2}$$ is:
  • $$6.02\times 10^{23}$$
  • $$6.02\times 10^{24}$$
  • $$1.806\times 10^{24}$$
  • $$18.06\times 10^{22}$$
In an experiment reproducing the measurements of Rutherford and his co-workers, $$22 \times 10^{-3}$$ mg of He gas was collected in one year from a sample of radium. This sample was observed to emit $$1.06 \times 10^{11} \alpha$$ - particles per second. Thus, Avogadro's number is?
  • $$5.92 \times 10^{23} mol^{-1}$$
  • $$6.92 \times 10^{23} mol^{-1}$$
  • $$6.08 \times 10^{23} mol^{-1}$$
  • $$6.58 \times 10^{23} mol^{-1}$$
A compound contains 3.2% of oxygen. The minimum molecular weight of the compound is:
  • 300 u
  • 440 u
  • 350 u
  • 500 u
In $$\overset { 14 }{ \underset { 7 }{ N }  } $$ if mass attributed to electron were doubled & the mass attributed to protons were halved, the atomic mass would become approximately:-
  • Halved
  • Doubled
  • Reduced by 25%
  • Remain same
Which of the following contains the largest mass of hydrogen atoms?
  • $$0.5$$ moles $$C_2H_2O_4$$
  • $$1.1$$ moles $$C_3H_8O_3$$
  • $$1.5$$ moles $$C_6H_8O_6$$
  • $$4.0$$ moles $$C_3H_8O_3$$
Haemoglobin contains $$4.6\%$$ of iron by mass. If the compound contains a single atom of iron then what is its molar mass in $$ { g\ mol }^{ -1 }$$?
  • $$1217.4$$
  • $$1324.7$$
  • $$1232.4$$
  • $$1317.5$$
A solution of 0.640 g of azulene in 100.0 g of benzene boils at $$80.23^0C$$. The boiling point of benzene is $$80.10^0C$$; the $$K_b$$ is $$ 2.53^0C/molal$$. What is the molecular weight of azulene?
  • 108
  • 99
  • 125
  • 134
Which of the following is the best example of law of conservation of mass?
[n and m are the masses of reactants and p and q are the masses of products formed.]
  • $$n-m=p-q$$
  • $$n+m=p+q$$
  • $$n=m$$
  • $$p=q$$
Molecular mass of  $${ Na }_{ 2 }{ SO }_{ 4 }$$ . $$10{ H }_{ 2 }O$$ is:
  • 320
  • 321
  • 322
  • 324
If Avogadro's number would have been $$1\times { 10 }^{ 23}$$, instead of $$6.02\times { 10 }^{ 23 }$$ then mass of one atom of $$_8^{16}O$$ would be:
  • $$1\ amu$$
  • $$1\times { 10 }^{ 10 }\ amu$$
  • $$16\ amu$$
  • $$6\times { 10 }^{ 13 }\ amu$$
Assertion: For the formation of a molecule at least two atoms are needed.
Reason: Molecules are formed by bonding between different atoms of different elements or complexes without any exception.
  • Both Assertion and Reason are true and Reason is correct explanation
  • Both Assertion and Reason are true and Reason is not correct explanation
  • Assertion is correct but Reason is wrong
  • Both Assertion and Reason are wrong
How many moles of helium gas occupy $$22.4L$$ at $$0^\circ C$$ at $$1$$ atm pressure?
  • $$0.11$$ mole
  • $$0.90$$ mole
  • $$1.0$$ mole
  • $$1.11$$ mole
Four different experiments were conducted in the following ways-

I) $$3g$$ of carbon was burnt in $$8g$$ of oxygen to give $$11g$$ of $$CO_2$$.

II) $$1.2g$$ of carbon was burnt in air to give $$4.2g$$ of $$CO_2$$.

III) $$4.5g$$ of carbon was burnt in enough air to give $$11g$$ of $$CO_2$$.

IV) $$4g$$ of carbon was burnt in oxygen to form $$30.3g$$ of $$CO_2$$.

Law of constant proportions is illustrated in which of the following experiment(s)?
  • I and III only
  • II and III only
  • IV only
  • I only
$${ K }_{ 4 }\left[ Fe\left( CN \right) _{ 6 } \right]$$ is supposed to be $$40$$ percent dissociated when $$1M$$ solution prepared. Its boiling point is equal to another $$20$$ percent mass by volume of non-electrolytic solution $$A$$ Considering molality=molarity . The molecular weight of $$A$$ is: 
  • $$77$$
  • $$67$$
  • $$57$$
  • $$47$$
A mixture of $$3\times10^{21}$$ molecules of $$X$$ and $$4.5\times10^{21}$$ molecules of $$Y$$ weigh $$1.375\ g$$. If the molecular weight of $$X$$ is $$50\ g$$, then what is the molecular weight of $$Y$$?
  • $$100$$
  • $$150$$
  • $$250$$
  • $$300$$
A box measures $$10\ cm \times 11.2\ cm \times 10\ cm$$. Assume that this box is filled with neon gas at $$1$$ atm pressure and $$273\ K$$ temperature. How many electrons will be there in the box ?
  • $$6.022\times 10^{23}$$
  • $$3.011\times 10^{23}$$
  • $$6.022\times 10^{22}$$
  • $$3.011\times 10^{22}$$
The total number of oxygen atoms in $$0.2mol$$ of $${Na}_{2}{B}_{4}{O}_{7}.10{H}_{2}O$$ will be?
  • $$6.02\times {10}^{23}$$
  • $$1.02\times {10}^{24}$$
  • $$2.05\times {10}^{24}$$
  • $$2.05\times {10}^{23}$$
What is the molecular mass of sodium sulphate?
  • 154
  • 119
  • 165
  • 142
If we consider that $$\frac{1}{6}$$, in place of $$\frac{1}{12}$$; mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will 
  • Decrease twice
  • Increase two fold
  • Remain unchanged
  • Be a function of the molecular mass of the substance
Number of electrons in 1.8 mL of $${H}_{2}O$$ are:
  • $$6.02 \times {10}^{23}$$
  • $$3.01 \times {10}^{24}$$
  • $$1.8 \times {10}^{23}$$
  • $$6.02 \times {10}^{25}$$
The molecular mass of $$K_2CO_3$$ is:
  • 128 u
  • 112 u
  • 116 u
  • 138 u
  • 90 u
If the atomic weight of oxygen were taken as $$90$$, then what would be the molecular weight of water?
  • $$101.25$$
  • $$104.52$$
  • $$112.5$$
  • $$142.5$$
Avogadro's number of helium atoms have a mass of
  • $$6.023\times 10^{23}g$$
  • $$4g$$
  • $$8g$$
  • $$4 \times\ 6.02 \times 10^{23}\ g$$
3 molecules of $$CO_{2}$$ weight
  • $$33\times10^{-23}$$ g
  • $$11\times10^{-23}$$ g
  • $$44\times10^{-23}$$ g
  • None of these
1 atomic mass unit is equal to:
  • $$\tfrac{1}{12}^{th}$$ mass of a carbon-12 atom
  • $$1.66\times 10^{-24}\ g$$
  • $$6.023\times 10^{-23}\ g$$
  • $$6.023\times 10^{23}\ g$$
A compound was found to contain $$5.37\%$$ nitrogen by mass. What is the minimum molecular weight of compound?
  • $$26.07$$
  • $$2.607$$
  • $$260.7$$
  • None
Who gave the definition of an element? 
  • Robert Boyle
  • John Dalton
  • Lavoisier
  • Thomson
$$12$$ gm of an alkaline earth metal gives $$14.8$$g of its nitride. The atomic mass of metal is:
  • $$12$$
  • $$24$$
  • $$20$$
  • $$40$$
A compound possesses 8% sulphur by mass. The least molecular mass is 
  • 100
  • 600
  • 400
  • 200
A sample of pure carbon dioxide, irrespective of its source contains $$27.27 \%$$ carbon and $$72.73 \%$$ oxygen. The given data supports: 
  • Law of constant proportions
  • Law of conservation of mass
  • Law of reciprocal proporties
  • Law of multiple proportions
The accepted unit of atomic and molecular mass is:
  • kilogram 
  • gram 
  • pound
  • atomic mass unit
If Avagadro Number $${N}_{A}$$ is changed from $$6.022\times{10}^{23}{mol}^{-1}$$ to $$6.022\times{10}^{20}{mol}^{-1}$$ this would change
  • The ratio of elements to each other in a compound
  • The definitiion of mass in units of grams
  • The mass of one mole of carbon
  • The ratio of chemical species to each other in a balanced equation
The weight of a molecule of compound $${C_{60}}{H_{22}}$$ is 
  • $$1.231 \times {10^{ - 21}}g$$
  • $$24 \times {10^{ - 21}}g$$
  • $$5.025 \times {10^{23}}g$$
  • $$16.023 \times {10^{23}}g$$
0:0:1


Answered Not Answered Not Visited Correct : 0 Incorrect : 0

Practice Class 9 Chemistry Quiz Questions and Answers