chap 7 key terms

Question 1

Avogadros constant

Answer 1

Avogadro’s constant- The number of particles in a mole; symbol NA = 6.02 x 1023 mol-1.

Question 2

carbon-12

Answer 2

Carbon-12- The isotope of carbon that has a mass number of 12. The isotope contains 6 protons and 6 neutrons. One atom of carbon-12 is taken as having a mass of exactly 12 units. This is the standard from which all other relative masses are calculated.

Question 3

empirical formula

Answer 3

Empirical formula- A formula that shows the simplest whole number ratio of the elements in a compounds, e.g. CH2 is the empirical formula of propene (C3H6).

Question 4

isotope

Answer 4

Isotope- Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons I their nuclei, e.g. 12C and 13C are isotopes of carbon.

Question 5

mass spectrometer

Answer 5

Mass spectrometer- An instrument that measures the ass-to-charge ratio of particles.

Question 6

mass spectrum

Answer 6

Mass spectrum- A graph of data produced from a mass spectrometer which shows the abundance or relative intensity of each particle, and their mass-to-charge, m/z, ratios.

Question 7

molar mass

Answer 7

Molar mass- The mass of 1 mole of a substance measured in g mol-1; symbol M.

Question 8

mole

Answer 8

Mole- The amount of substance that contains the same number of fundamental particles as there are atoms in 12 g of carbon-12; symbol n; unit mol.

Question 9

molecular formula

Answer 9

Molecular formula- A formula of a compound that gives the actual number and type of atoms present in a molecule. It may be the same as or different from the empirical formula.

Question 10

molecule

Answer 10

Molecule- A group of two or more atoms covalently bonded together, and representing the smallest fundamental unit of a chemical compound.

Question 11

percentage composition

Answer 11

Percentage composition- A calculation which compares experimental results to accepted or theoretical results and expresses them as a percentage.

Question 12

relative isotopic abundance

Answer 12

Relative isotopic abundance- The percentage abundance of a particular isotope in a sample of an element.

Question 13

relative atomic mass

Answer 13

Relative atomic mass- The weighted average of the relative isotopic masses of an element on the scale where 12C is 12 units exactly; symbol Ar.

Question 14

relative isotopic mass

Answer 14

Relative isotopic mass- The mass of an atom of the isotope relative to the mass of an atom of carbon-1 taken as 12 units exactly.

Question 15

relative mass

Answer 15

Relative mass- The mass of an atom, molecule or compounds relative to the mass of an atom of 12C, taken 12 units exactly.