Mole Concept

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Q1. If 1 mole of a gas occupies 22.4 liters at STP, how many liters will 0.5 moles occupy? (2023)

Solution:

At STP, 1 mole of gas occupies 22.4 L. Therefore, 0.5 moles will occupy 0.5 x 22.4 L = 11.2 L.

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Q2. If you have 0.25 moles of sulfuric acid (H2SO4), what is its mass? (2023)

Solution:

Molar mass of H2SO4 = 2*1 + 32 + 4*16 = 98 g/mol. Mass = 0.25 moles x 98 g/mol = 24.5 g.

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Q3. What is the number of moles in 44 grams of CO2? (2021) 2021

Solution:

Molar mass of CO2 = 12 + 16*2 = 44 g/mol. Number of moles = mass/molar mass = 44g/44g/mol = 1 mole.

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Q4. How many grams are in 4 moles of sulfuric acid (H2SO4)? (2023)

Solution:

Molar mass of H2SO4 = 2*1 + 32 + 4*16 = 98 g/mol. Mass = 4 moles x 98 g/mol = 392 g.

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Q5. What is the mass of 3 moles of sodium chloride (NaCl)? (2023)

Solution:

The molar mass of NaCl is 58.5 g/mol. Therefore, 3 moles of NaCl weigh 3 x 58.5 g = 175.5 g.

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Q6. How many molecules are in 0.1 moles of oxygen gas (O2)? (2021)

Solution:

Number of molecules = moles x Avogadro's number = 0.1 moles x 6.022 x 10^23 molecules/mole = 6.022 x 10^22 molecules.

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Q7. What is the number of moles in 10 grams of H2? (2020)

Solution:

Molar mass of H2 = 2 g/mol. Number of moles = mass/molar mass = 10 g / 2 g/mol = 5 moles.

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Q8. What is the mass of 3 moles of NaCl? (2020) 2020

Solution:

Molar mass of NaCl = 23 + 35.5 = 58.5 g/mol. Mass = moles x molar mass = 3 moles x 58.5 g/mol = 174 g.

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Q9. How many molecules are present in 2 moles of water (H2O)? (2022) 2022

Solution:

Number of molecules = moles x Avogadro's number = 2 moles x 6.022 x 10^23 molecules/mole = 1.2044 x 10^24 molecules.

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Q10. If 0.5 moles of a gas occupy 12 liters at STP, what is the molar volume of the gas? (2023)

Solution:

At STP, 1 mole of any gas occupies 22.4 L. Therefore, 0.5 moles occupy 0.5 x 22.4 L = 11.2 L, confirming the molar volume is 22.4 L.