FC2 Moles I

Question 1

Define an isotope

Answer 1

Isotopes are atoms which have the same number of protons but a different number of neutrons and electrons

Question 1

Define relative isotopic mass

Answer 1

Is the mass of an atom of the isotope compared with 1/12 of the mass of an atom of carbon-12

Question 2

Define relative atomic mass

Answer 2

Is the WEIGHTED MEAN mass of an atom of an element compared with 1/12 of the mass of an atom of carbon-12

Question 3

How do you calculate relative atomic mass

Answer 3

• For each isotope multiply mass number x relative amount
• Add these numbers together
• Divide the total by the sum of the relative amounts
  (often the relative amounts are given as % figures- in which case you divide by 100)

Question 4

What is a mass spectrometer

Answer 4

Is a device which makes it possible to measure the mass of an individual atom or molecule and, therefore, to count the relative numbers of atoms of a given mass in a sample

Question 5

Define relative molecular mass

Answer 5

The Mr of a substance is the WEIGHTED MEAN mass of a molecule of that substance compared to 1/12 of the mass of an atom of carbon-12

Question 6

Define relative formula mass

Answer 6

The Mr of a substance is the average mass of a formula unit of that substance compared to 1/12 of the mass of an atom of carbon-12

Question 7

Define a mole

Answer 7

A mole is the amount of a substance that contains 6.02 x 10^23 particles (the ‘particles’ may be atoms, molecules, ions, or formula units- depending on what substance we are concerned with)

Question 8

Define molar mass

Answer 8

Is the mass (in grams) of 1 mole of a substance. The units of molar mass are g/mol

Question 9

What is the calculation involving moles, mass, and Mr

Answer 9

moles = mass/Mr

Question 10

What is the calculation involving moles, number of particles, and Avogadro’s constant

Answer 10

moles = number of particles/ Avogadro’s constant