Atoms and reactions

Question 1

What’s the structure of the plum pudding model

Answer 1

Negative electrons moving around in a ‘sea’ of positive charge. Neutral charge overall

Question 2

What did Rutherford’s gold leaf experiment show?

Answer 2

positive charge of an atom and most of its mass is concentrated in a nucleus at the centre. negative electrons orbit the nucleus and most of the atom’s volume is the space between the nucleus and orbiting electrons

Question 3

Where are protons and neutrons found?

Answer 3

in nucleus

Question 4

what is the relative mass and charge of a proton, neutron and electron?

Answer 4

Proton = +1 charge, 1.0 relative mass
Electron = -1 charge, 1/2000 relative mass
Neutron = 0 charge, 1.0 relative mass.

Question 5

What are isotopes of the same element?

Answer 5

elements with the same number of protons and electrons but different numbers of neutrons in the nucleus (and therefore different masses)

Question 6

What is the atomic number

Answer 6

number of protons in the nucleus

Question 7

what is the mass number

Answer 7

number of particles (protons and nuetrons) In the nucleus

Question 8

Why do different isotopes of the same elements react in the same way?

Answer 8

chemical reactions involve electrons and isotopes have the same number + arrangements of electrons

neutrons make no difference to chemical reactivity

Question 9

define relative isotopic mass

Answer 9

mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon-12

Question 10

define relative atomic mass

Answer 10

the weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12

Question 11

which measurement of mass do you use when describing simple molecules

Answer 11

relative molecular mass

Question 12

which measurement of mass do you use when describing giant structures

Answer 12

relative formula mass

Question 13

What is mass spectrometry used to identify? 3 things.

Answer 13

identify an unknown compound
find the relative abundance of each isotope of an element
determine structural information about molecules

Question 14

What is on the x and y axis for a mass spectrum graph? google if unfamiliar

Answer 14

y axis = percentage abundance
x axis = mass/charge ratio (m/z)

N.B. charge is usually 1

Question 15

How can you predict the charge on an element’s ion from its position in the periodic table?

Answer 15

the number of electrons in the outer shell is the same as the group number of an element. e.g. lithium is in group one with one electron in its outer shell.

Question 16

What elements don’t usually form ions and why?

Answer 16

Be, B, C and Si:

It requires too much energy to transfer the outer shell electrons to form ions.

Question 17

Which elements form more than one ion?

Answer 17

iron (2+ and 3+)

copper (1+ and 2+)

Question 18

What are molecular ions?

Answer 18

When groups of covalently bonded atoms can lose or gain electrons to form ions. The charge on a molecular ion can be considered as being shared out across the entire molecule.

Question 19

What’s the formulae for these common molecular ions:

Ammonium
Hydroxide
Nitrate
Carbonate
Sulfate

Answer 19

Ammonium -> NH4 +
Hydroxide -> OH -
Nitrate -> NO3 -
Carbonate -> CO3 2-
Sulfate -> SO4 2-

Question 20

What must the overall charge for an ionic compound always be?

Answer 20

Zero

Question 21

What is Avogadro constant

Answer 21

number of atoms per mole of carbon 12 (6.02 x 10^23)

Question 22

What equation links together molar mass, mass and moles?

Answer 22

mass = moles x molar mass

Question 23

What’s an empirical formula?

Answer 23

the ratio between elements rather than the actual number of atoms of each elements.

Question 24

Why is empirical formula used for giant structure compounds?

Answer 24

showing the actual formula would run into the millions of millions -> too big and complicated so we simplify it down to the most basic ratio

Question 25

What is molecular formula?

Answer 25

molecular formula tells you the number of each type of atom that makes up a molecule

Question 26

What is the molar gas volume?

Answer 26

the volume per mole of a gas. At room temperature and pressure, the molar volume is approximately 24.0dm^3mol^-1

Question 27

What is the ideal gas equation (GIVE THE STANDARDISED UNITS)

Answer 27

PV=nRT`
Pressure = Pascales 
Volume = Cubic metres
Temperature = Kelvin
R = Always 8.314 (will be given to you in questions)

Question 28

Define concentration

Answer 28

amount of solute in mol dissolved per 1 dm^3 of solution

Question 29

Define standard solution

Answer 29

solution of known concentration. usually used in titrations to determine unknown information about another substance.

Question 30

What does 2M mean?

Answer 30

2mol dm^-3 concentration

Question 31

How do you calculate percentage yield?

Answer 31

actual amount in mol of product / theoretical amount in mol of product

x 100

Question 32

what are limitations of percentage yield

Answer 32

doesn’t take into account waste products formed

Question 33

how do you calculate atom economy

Answer 33

molecular mass of the desired product / sum of molecular masses of all products

x 100

Question 34

What does a high atom economy describe?

Answer 34

reaction that uses atoms with minimal waste.