Atoms and Molecules Worksheet-3

Atoms and Molecules Worksheet-3

 

  1. What is the chemical formula of Sodium oxide and sodium sulphide?

A. NaO and Na2S                          B. Na2O and NaS2

C. NaO2 and Na2S                        D. Na2O and Na2S

 

  1. The name of the compound represented by chemical formula Al2(SO4)3 is ______.

A. Aluminium sulphate               B. Aluminium sulphite

C. Aluminium sulphide               D. Aluminium thiosulphate

 

  1. The name of the compound represented by chemical formula CaCO3 is _____

A. Calcium bicarbonate

B. Calcium carbonate

C. Calcium hydrogen carbonate

 

  1. The name of the compound represented by chemical formula K2SO4 is _____

A. Potassium sulphite

B. Potassium sulphide

C. Potassium hydrogen sulphate

D. Potassium sulphate

 

  1. What is the molar masses of CH3OH ?

A. 33 u                B. 24 u                C. 32 u                D. 31 u

 

  1. Calculate the formula unit mass of K2CO3.

K = 39 u, C = 12 u and O = 16 u

A. 138 u              B. 132 u              C. 122 u

 

  1. Which of the following has more number of atoms?

(a) 100 grams of sodium (b) 100 grams of iron

(Given : atomic mass of Na = 23u ; Fe = 56u)

A. 100 grams of iron contains more number of atoms

B. 100 grams of sodium contains more number of atoms

C. 100 grams of sodium and 100 grams of iron contain equal number of atoms

 

  1. Calculate the molar mass of Nitric acid, HNO3.

A. 63 u                B. 36 u                C. 60 u               D. 66 u

 

  1. How many moles are present in 22 g of carbon dioxide?

A. 1 mole            B. 0.1 mole        C. 0.5 mole        D. 0.25 mole

 

  1. How many particles are present in 0.25 mole of an element?

A. 0.240 × 1023 particles            B. 0.240 × 1023 particles

C. 2.05 × 1023 particles               D. 6.022 × 1023 particles

 

  1. Out of 4g of methane (CH4) and 11g of CO2, which has more number of molecules?       

A. 4g of methane (CH4) has more number of molecules

B. 11g of CO2 has more number of molecules

C. Both have same number of molecules

 

  1. Four samples of carbon dioxide (CO2) were prepared by using different methods. Each sample on analysis was found to contain 37.5% carbon. Which law is in agreement with this observation?

A. Law of conservation of mass

B. Law of constant proportions

C. Law of reciprocal proportions

D. Law of multiple proportions

 

  1. Which of the following statement is incorrect related to ‘1 mole of hydrogen molecules’?

A. 6.022 × 1023 molecules are present in 1 mole of hydrogen molecule

B. Gram molecular mass of 1 mole of Hydrogen molecule is 2g

C. 2 × 6.022 × 1023 atoms are present in 1 mole of Hydrogen molecules

D. None of these

 

  1. 10 g of sulphur dioxide (SO2) or 10g of oxygen (O2) which of them have more number of molecules?

A. 10 g of sulphur dioxide (SO2)

B. 10g of oxygen (O2)

C. Both have same number of molecules

 

  1. An element X shows variable valencies 4 and 6. Write the formulae of its two oxides.

A. XO2 and XO3                            B. X4O2 and X6O2

C. XO2 and X3O6                          D. XO and XO3

 

  1. A flask P contains 0.5 mole of oxygen gas. Another flask Q Contains 0.4 mole of ozone gas. Which of the two flasks contains more number of oxygen atoms?

A. Flask P

B. Both contain same number of oxygen atoms

C. Flask Q

 

Answer:

  1. D

Explanation:

         

 

  1. A

Explanation: Aluminium sulphate

 

  1. B

Explanation: Calcium carbonate.

 

  1. D

Explanation: Potassium sulphate

 

  1. C

Explanation: Methyl alcohol (CH3OH)

Molar mass of CH3OH = (1 × atomic mass of C) + (4 × atomic mass of H) + (1 × atomic mass of O)

          = (1 × 12u) + (4 × 1u) + (1 × 16u) = 32u

 

  1. A

Explanation: Formula unit mass of K2CO3 (Potassium carbonate).

= (2 × atomic mass of K) + (1 × atomic mass of C) + (3 × atomic mass of O)

= (2 × 39u) + (1 × 12u) + (3 × 16u) = 138u

 

  1. B

Explanation: (a) 100 grams of sodium

No. of atoms of sodium = Number of moles × (avogadro's number)

(b) 100 grams of iron

No. of atoms of iron = Number of moles × (Avogadro's number)

100 g of sodium has more number of atoms

 

  1. A

Explanation: Nitric acid, HNO3

Molar mass of HNO3 = (1 × atomic mass of H) + (1 × atomic mass of N) + (3 × atomic mass of O)

= (1 × 1u) + (1 × 14u) + (3 × 16u) = 36u.

 

  1. C

Explanation: 22 g of carbon dioxide (CO2)

Molar mass of carbon dioxide (CO2) = (1 × 12u) + (2 × 16u) = 44u

Gram molecular mass = 44g

44 g of carbon dioxide (CO2)= 1 mol

22g of carbon dioxide (CO2)

 

  1. B

Explanation: 1.0 mole of the element represents particles = 6.022 × 1023

0.25 mole of the element represents particles

= 1.505 × 1023 particles

 

  1. C

Explanation: Number of moles in 4 g of methane (CH4)

Number of moles in 11 g of CO2

Since both CH4 and CO2 have same number of moles (0.25 mol), they have same number of molecules also.

 

  1. B

Explanation: Carbon dioxide consists of carbon and oxygen. Elements combine in a fixed ratio to form a compound. According to the Law of constant proportions the composition of a compound remains the same irrespective of the source. Since the percentage of carbon in each sample is fixed, that of oxygen must be also fixed. This is according to law of constant proportions.

 

  1. D

Explanation: All the statements are correct.

 

  1. B

Explanation: Number of molecules in 10 g of sulphur dioxide (SO2)

Molar mass of SO2 = 32g + 2 × 16g = 64g

Number of molecules of sulphur dioxide in 64 g of sulphur dioxide = 6.022 × 1023

Number of molecules of sulphur dioxide in 10 g of sulphur dioxide                                                                   

         

No. of molecules in 10 g oxygen

Molar mass of oxygen (O2) = 32g

32 g of oxygen represent molecules = 6.022 × 1023

10 g of oxygen represent molecules

         

Thus, 10 g of oxygen (O2) has more molecules than 10g of (SO2)

 

  1. A

Explanation: Let the element be X

Formula of oxide in which valency of X is 4 = X2O4 or XO2

Formula of oxide in which valency of X is 6 = X2O6 or XO3

 

  1. C

Explanation:

1 molecule of oxygen (O2) = 2 atoms of oxygen

1 molecule of ozone (O3) = 3 atoms of oxygen

In flask P : 1 mole of oxygen gas = 6.022 × 1023 molecules

               0.5 mole of oxygen gas = 6.022 × 1023 × 0.5 molecules

                   = 6.022 × 1023 × 0.5 × 2 atoms

                   = 6.022 × 1023 atoms

 

In flask Q : 1 mole of ozone gas = 6.022 × 1023 molecules

                   0.4 mole of ozone gas = 6.022 × 1023 × 0.4 molecules

                   = 6.022 × 1023 × 0.4 × 3 atoms

                   = 7.23 × 1023 atoms

∴ Flask Q has a greater number of oxygen atoms as compared to flask P.