A mixture of gases contains H2 and O2 gases in the ratio of 1:4 (w/w). What is the molar

ratio of the two gases in the mixture?

1. 1:4             

2. 4:1             

3. 16:1               

4. 2:1

Subtopic:  Moles, Atoms & Electrons |
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If Avogadro number NA, is changed from 6.022 x 1023 mol-1 to 6.022 x 1020 mol-1 this

would change

1. the definition of mass in units of grams

2. the mass of one mole of carbon

3. the ratio of chemical species to each other in a balanced equation

4. the ratio of elements to each other in a compound

Subtopic:  Moles, Atoms & Electrons |
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20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide

and 8.0 g magnesium oxide. What will be the percentage purity of magnesium carbonate

in the sample? (Atomic weight of Mg = 24)

1. 75

2. 96

3. 60

4. 84

Subtopic:  Equation Based Problem |
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What is the mass of precipitate formed when 50 mL of 16.9% solution of AgNO3 is mixed

with 50 mL of 5.8% NaCl solution?

(Ag = 107.8, N = 14, O = 16, Na= 23,Cl=35.5)

1. 28 g

2. 3.5 g

3. 7 g

4. 14 g

Subtopic:  Equation Based Problem |
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When 22.4 L of H2 (g) is mixed with 11.2 L of Cl2 (g), each at STP, the moles of HCl(g)

formed is equal to

1. 1 mole of HCl (g)

2. 2 moles of HCl (g)

3. 0.5 mole of HCl (g)

4. 1.5 mole of HCl (g)

Subtopic:  Limiting Reagent |
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25.3 g of Sodium carbonate Na2CO3 is dissolved in enough water to make 250 mL of

solution. If sodium carbonate dissociates completely, molar concentration of sodium ion,

Na+ and carbonate ion CO32- are respectively (Molar mass of Na2CO3 = 106 g mol-1)

1. 0.955 M and 1.910 M

2. 1.910 M and 0.955 M

3. 1.90 M and 1.910 M

4. 0.477 M and 0.477 M

Subtopic:  Concentration Based Problem |
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The number of atoms in 0.1 mole of a triatomic gas is (NA=6.02 x1023mol-1)

1. 6.026 x 1022 

2. 1.806x1023

3. 3.600 x 1023

4. 1.800 x 1022

Subtopic:  Moles, Atoms & Electrons |
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An organic compound contains carbon, hydrogen, and oxygen. Its elemental analysis gave C, 38.7% and H, 9.67%. The empirical formula of the compound would be

1. CH3O                                   

2. CH2O

3. CHO                                     

4. CH4O

Subtopic:  Empirical & Molecular Formula |
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How many moles of lead (II) chloride will be formed from a reaction between 6.5g of PbO and 3.2g of HCl?

(1) 0.044                           

(2) 0.333

(3) 0.011                           

(4) 0.029

Subtopic:  Equation Based Problem |
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Concentrated aqueous sulphuric acid is 98% H2SO4 by mass and has a density of 1.80 g mL-1. Volume of acid required to make one litre of 0.1 M H2S04 solution is :

(1) 11.10 mL

(2) 16.65 mL

(3) 22.20 mL

(4) 5.55 mL

Subtopic:  Concentration Based Problem |
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