Foundations (Mod 2)

Question 1

What is the atomic number?

Answer 1

The number of protons in the nucleus

Question 2

What is an isotope?

Answer 2

Isotopes are atoms of the same element with different numbers of neutrons in the nucleus

Question 3

Do isotopes have different chemical reactions?

Answer 3

No, isotopes of the same element only differ in the number of neutrons, which have no effect on chemical reactions. (There may be differences in physical properties)

Question 4

What is an ion?

Answer 4

An ion is a charged atom. (Different proton:electron ratio)

Question 5

What is relative isotopic mass?

Answer 5

Relative isotopic mass is the mass of an isotope relative to 1/12th of the mass of an atom of carbon-12

Question 6

What is relative atomic mass?

Answer 6

Relative atomic mass is the weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12

Question 7

How is a mass spectrometer used to determine relative atomic mass

Answer 7

• A sample is placed in the mass spectrometer
• The sample is vaporized and then ionized to form + ions
• The ions are accelerated, heavy ions move slower#
• The separated ions are detected on a mass spectrum as a mass to charge ratio
• Each ion that reaches the detector adds to the signal, so the greater the abundance, the larger the signal.

Question 8

What is the mass to charge ratio?

Answer 8

M/Z = Relative mass of ion/Relative charge of ion
(if the charge is +1 then it’s just a graph of relative isotopic mass) however if the charges are higher then remember to divide

Question 9

How many atoms are in a mole?

Answer 9

6.02x10^23

Question 10

What is molar mass?

Answer 10

Molar mass is the mass per mole of a substance (g/mol)

Question 11

What is a molecular formula?

Answer 11

The molecular is the number of atoms of each element in an atom. e.g. H2O, C6H12O6.

Question 12

What is an empirical formula?

Answer 12

The empirical formula is the simplest whole number ratio of atoms of each element in a compound.

Question 13

What is relative molecular mass?

Answer 13

Mr compares the mass of a molecule with the mass of a carbon-12 atom

Question 14

What is relative formula mass?

Answer 14

Relative formula mass compares the mass of a formula unit with the mass of a carbon-12 atom.

Question 15

What is a standard solution?

Answer 15

A standard solution is a solution of known concentration

Question 16

What are the conditions for the ideal gas equation?

Answer 16

• R (ideal gas constant) 8.314j/mol/k
• Temperature (Kelvin)
• Volume (m^3)
• Pressure (Pascals)
• n, (moles of gas)

Question 17

What assumptions are made of the gas molecules?

Answer 17

• Random motion
• Elastic collisions
• Negligible size
• No intermolecular forces

Question 18

What is the math behind each conversion?:

• cm^3 to m^3
• dm^3 to m^3
• Centigrade to Kelvin
• KPa to Pa

Answer 18

• cm^3 to m^3 = x10^-6
• dm^3 to m^3 = x10^-3
• Centigrade to Kelvin = +273
• KPa to Pa = x10^3

Question 19

What is the real gas equation and what does it signify?

Answer 19

(p+n^2a/v^2)(V-nb)=nRT

• The n^2a/v^2 accounts for intermolecular forces
• The -nb accounts for volume of gas molecules

Question 20

What is stoichiometry?

Answer 20

the ratio of balancing numbers (moles) of an equation

Question 21

What is a limiting reagent?

Answer 21

The reactant that is not in excess, which will be completely used up first thus stopping a reaction.

Question 22

What is atom economy?

Answer 22

The atom economy of a chemical reaction is a measure of how well atoms have been utilised.