Introduction to Moles

How many moles are in 6.02 x 10²³ molecules of H₂O?

• 1 mole

• 2 moles

• 6.02 moles

• 602000000000000000000000 moles

Avogadro's number of particles in a mole holds true for:

• Ions

• Molecules

• Atoms

• All of these

Avogadro's number varies according to the particles in one mole of the substance.

• TRUE

• FALSE

One mole of hydrogen atoms has the same mass as Avogadro's number of hydrogen atoms.

• TRUE

• FALSE

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NGSS.HS-PS1-7

How many moles of Cl₂ must react to produce 12.3 g of AlCl₃?

Answer explanation

12.3 g AlCl₃ = 0.0922 mol AlCl₃ (12.3/133.34 g/mol) Ratio of AlCl₃ : Cl₂ is 2:3 so (0.0922 * 3)/2 = 0.1383.

12.3g is 3 sigfig, so 0.138 mol

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NGSS.HS-PS1-7

How many moles of N₂ will be produced if 3.5 moles of O₂

react?

Answer explanation

Ratio of O₂:N₂ is 3:2. so (3.5*2)/3 = 2.333. 3.5 is 2 sigfig so 2.3 mol

How many grams of carbon dioxide will be produced if 3.5 moles of O₂ react?

Answer explanation

Mole ratio of O₂:CO₂ is 13:8. So (3.5*8)/13 = 2.1538 mol of CO₂. Molar mass of CO₂ is 44.01 g/mol so (2.1538mol*44.01g/mol) = 94.79g. 2 sigfig so 95g

Based on this equation, if you have 10 mol of carbon disulfide (CS₂) and 25 mol of oxygen (O₂) which would be your limiting reactant?

Answer explanation

The time may seem too short here, but no advanced calculations are needed. The ratio of carbon disulfide and oxygen is 1:3. So 10 mol of CS₂ would need 30 mol of O_{2 .} Since we only have 25 mol of O₂ we will run out of it, making it the limiting reactant.

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NGSS.HS-PS1-7

If I have 400g of Cl₂ and 300g of Al, how many grams of AlCl₃ will I produce?

Answer explanation

400g of Cl₂ makes 3.76 mol AlCl₃

300g of Al makes 11.119 mol of AlCl₃.

Cl₂ is limiting

3.76 mol of AlCl₃ = 501.35 g AlCl₃ = 501g

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NGSS.HS-PS1-7

Avogadro's number of representative particles is equal to one_____

• kilogram

• gram

• kelvin

• mole

Tags

NGSS.HS-PS1-7