Chemistry: Avogadro's Number and Moles
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Questions and Answers

What is the relative molecular mass of water, H2O?

  • 24
  • 16
  • 20
  • 18 (correct)

What is the mass of one mole of hydrated copper(II) sulfate, CuSO4.5H2O?

  • 200 grams
  • 300 grams
  • 180 grams
  • 249.5 grams (correct)

How many moles are there in 36 g of carbon atoms?

  • 3 moles (correct)
  • 4 moles
  • 1 mole
  • 2 moles

What is the relative molecular mass of sulfuric acid, H2SO4?

<p>98 (D)</p> Signup and view all the answers

How many moles of water molecules are in 117 g of water?

<p>6.5 moles (D)</p> Signup and view all the answers

How many atoms are present in 0.25 moles of sodium, Na?

<p>3.0 x 10^23 atoms (B)</p> Signup and view all the answers

What is the process for converting grams of a compound to moles?

<p>Mass of the compound divided by its relative molecular mass (D)</p> Signup and view all the answers

What is the mass of one mole of sodium chloride, NaCl?

<p>58.5 grams (B)</p> Signup and view all the answers

What does one mole of a substance represent?

<p>6 x 10^23 molecules or atoms of the substance (A)</p> Signup and view all the answers

What is the mass of one mole of Carbon?

<p>12 grams (D)</p> Signup and view all the answers

How many grams are there in three moles of Aluminium?

<p>81 grams (B)</p> Signup and view all the answers

Which of the following elements has the highest relative atomic mass?

<p>Silver (B)</p> Signup and view all the answers

What is the relative atomic mass of Oxygen?

<p>16 (D)</p> Signup and view all the answers

If one mole of Sodium weighs 23 grams, what would five moles weigh?

<p>115 grams (D)</p> Signup and view all the answers

Which option correctly expresses Avogadro's number?

<p>6 x 10^23 (D)</p> Signup and view all the answers

What do you obtain by adding up all the relative atomic masses of atoms in a molecule?

<p>Relative molecular mass of the compound (D)</p> Signup and view all the answers

Flashcards

One mole of an element

The amount of an element containing 6 x 10^23 atoms.

Avogadro's Number

A constant, 6 x 10^23, representing the number of particles in one mole.

Mass of one mole (element)

The mass (in grams) equal to the element's relative atomic mass.

Relative Atomic Mass

The average mass of an atom of an element compared to 1/12 the mass of a carbon-12 atom.

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Finding mass (multiple moles)

Multiply the mass of one mole of the substance by the number of moles.

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Mole Concept

A way to count atoms and molecules in chemistry.

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Relative Molecular Mass

Sum of the relative atomic masses of all atoms in a molecule.

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Converting moles to grams

Multiply the number of moles by the relative atomic mass in grams for an element or the relative molecular weight in grams for a compound.

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Relative Molecular Mass (RMM)

The average mass of one molecule of a compound compared to one-twelfth the mass of a carbon-12 atom.

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Mass of one mole

The mass in grams of one mole of a substance, equal to its relative molecular mass (RMM) in grams.

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Number of moles (n)

A measure of the amount of a substance, calculated by dividing the mass of a substance by its relative atomic/molecular mass.

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Moles to atoms/molecules

One mole of any substance contains Avogadro's number (6.02 x 10^23) of particles (atoms or molecules).

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Calculating Moles of Water

To find the number of moles, divide the mass of water (in grams) by its relative molecular mass (18 g/mol).

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Moles of an element

Number of moles = mass of element / relative atomic mass

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Calculating Moles of H₂SO₄

Find moles of sulfuric acid by dividing the mass of H₂SO₄ by its relative molecular mass (approximately 98 g/mol).

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Moles to Atoms

Multiply the number of moles by Avogadro's number (6.02 x 10²³) to find the number of atoms.

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Study Notes

Avogadro's Number and the Mole Concept

  • Avogadro developed a method for counting atoms and molecules.
  • If elements are weighed in proportions equal to their relative atomic masses, the same number of atoms will be present.
  • Avogadro's number (L) is 6 x 1023 atoms/molecules per mole.
  • One mole of a substance contains 6 x 1023 particles of that substance.

Converting Moles to Grams

  • Mass of one mole of an element = Relative Atomic Mass in grams.
  • For example, one mole of sodium (Na) is 23 grams.

Relative Atomic Mass

  • Relative Atomic Mass is based on the carbon-12 isotope.
  • The relative molecular mass of a compound is calculated by summing the relative atomic masses of all atoms in the molecule.

Calculating Masses of Moles of Elements

  • To find the mass of a certain number of moles of an element, multiply the number of moles by the element's relative atomic mass.

Examples

  • Calculate the mass of three moles of aluminum (Al) atoms.
    • 1 mole of Al has a mass of 27 grams
    • 3 moles of Al = (27 g/mole) × (3 moles) = 81 grams
  • Calculate the number of moles in 36 grams of carbon (C) atoms.
    • 1 mole of C has a mass of 12 grams
    • No. of moles = (36 g) ÷ (12 g/mole) = 3 moles

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The Mole Concept PDF

Description

Test your understanding of Avogadro's number and the mole concept in chemistry. This quiz covers the relationships between moles, grams, and relative atomic mass, along with calculation techniques. Perfect for students looking to solidify their knowledge of foundational chemistry concepts.

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