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Fundamental of Chemistry: Multiple choice questions (MCQs) and answer with explanation

1. Which of the following list contains only elements ?





... Answer is d)
Explanation: calcium, carbon and sulphur are only elements.In option a) air is an example of mixture and water is example of compound. In option b) brass is a mixture. In option c) air, fire and earth are examples of mixture and water is a compound.



2. The diagrams below represent particles in four substances, which box represents the particles of nitrogen





... Answer is d)
Explanation: Particles of any pure substace are similar. Hence, diagram d contain similar diatomic molecules, so it represents particles of Nitrogen.

3. What is the formula mass of CuSO4​​.5 H​​​​2​​O (atomic mass are: Cu = 63.5, S = 32, O = 16, H = 1?





... Answer is c)
Explanation: Formula mass of CuSO4​​.5 H​​​​2​​O = Atomic mass of Cu + Atomic mass of S + 4 ×(Atomic mass of O) + 5 ×[ 2×(Atomic mass of H)+ Atomic mass of O] = 63.5 + 32 + 4 (16) + 5 (16+2) = 249.5

4. A compound chemical formula Na2CX3 has formula mass 106 amu. Atomic mass of the element X is?





... Answer is d)
Explanation:Formula mass of Na2CX3 = 2(Atomic mass of Na) + Atomic mass of C + 3(Atomic mass of X) = 106 amu 2(23) + 12 + 3X = 106 68 + 3X = 106 3x = 106-68 X = 48/3 = 16 amu

5. How many moles of molecules are there in 16 gram oxygen?





... Answer is b)
Explanation: Thermostate is a modern word derived from two Greek words thermo (heat) and statos (same). So, from its name one can easily conclude that thermostat is something that maintains the temperature.

6. What is the mass of 4 mole of hydrogen gas?





... Answer is a)
Explanation: No. of moles of H2 = 4 moles Molar mass of H2 = 2 gmol-1 Hence, No. of moles of H2 = Mass of H2/ Molar mass of H2 Mass of H2 = No. of moles of H2 × molar mass of H2 = 4 × 2 = 8 g

7. What is the mass of carbon present in 44 gram of carbon dioxide?





... Answer is a)
Explanation: mass of CO2 = 44g Molar mass of CO2 = 44 gmol-1 Hence, No. of moles of CO2 = Mass of CO2/ Molar mass of CO2 No. of moles of CO2 = 44/44 No. of moles of CO2 = 1 mole1 moles of CO2 = 1mole of C 1 moles of CO2 = 1mole × molar mass of C 1 moles of CO2 = 1mole × 12 g/mole = 12 g

8. The electronic configuration of an element is 1S2​​​​​​, 2S2. An atom of this element will form an ion that will have charge?





... Answer is b)
Explanation: From electronic configuration, it is clear that atom has 2 electrons in its valence shell. So this atom will lose two electons to form dipositive cation.

9. Which term is the same for one mole of oxygen and one mole of water?





... Answer is d)
Explanation: Equal moles of different substances have same number of particles (moleucules, atoms or ions). As both oxygen and water exist in molecular form, so both have same number of molecules.

10. If one mole of carbon contains X atoms what is the number of atoms contain in 12 gram of magnesium?





... Answerq10 b)
Explanation: mass of Mg = 12g Molar mass of Mg = 24 gmol-1 Hence, No. of moles of Mg = Mass of Mg/ Molar mass of Mg No. of moles of Mg = 12/24 No. of moles of Mg = 0.5 moleNo. of Mg atoms = 0.5 × X = 0.5X As 1 mole = X atoms.
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