Topic 5: Formulae, Equations and Amounts of Substance

Question 1

define atom

Answer 1

the smallest unit of an element that can exist

Question 2

define molecule

Answer 2

the smallest part of an element or a compound which can exist alone under normal conditions

Question 3

define ion

Answer 3

an atom or group of atoms possessing a negative charge

Question 4

define element

Answer 4

a substance containing just one type of atom

Question 5

define compound

Answer 5

a substance that contains different elements that have been chemically bonded

Question 6

define empirical formulae

Answer 6

the simplest ratio showing the different types of atom present in a substance

Question 7

define molecular formulae

Answer 7

the actual numbers of each type of atom in a molecule of the substance

Question 8

what is avogadros constant

Answer 8

6.02 x 10^23

Question 9

equation using avogadros constant

Answer 9

No of particles = amount of substance (in mol) X Avogadro’s constant

Question 10

moles formula

Answer 10

moles = mass / RFM

Question 11

moles of gas formula

Answer 11

moles of gas = volume / molar volume in dm3

Question 12

concentration formula

Answer 12

conc = mols / volume in dm3

Question 13

percentage yield formula

Answer 13

percentage yield = mass of material produced / theoretical max mass x 100

Question 14

percentage atom economy

Answer 14

molar mass of useful product / total molar mass of starting materials x 100

Question 15

PV= nRT

Answer 15

P= pressure in Pa 
V= volume in m3
n= moles 
R= gas constant (8.314 J K-1 Mol-1)
T= temperature in K (-273 degrees = 0K)