Unit 3) molecular structure

Question 1

what is empirical formula

Answer 1

shows the elements present in the compound, and the simplest ratio of the atoms of these elements in the compound. eg ethene c2h6 has an empirical formula ,CH3

Question 2

• what is molecular formula/chemical formula

- how can it be worked out if you know the empirical formula and the relative molecular mass

Answer 2

• shows the actual number of each kind of atom present in a molecule of the compound
• eg if the empirical formula is ch2o6, and relative molecular mass is 60- empirical mass will be 30(12+2+16) , which is half the molecular mass. so the molecular formula must be twice the empirical formula eg 2 x ch2o6= c2h4o2

Question 3

structural formula

• full
• abbreviated /shortened

Answer 3

• structural formula shows the number of each kind of atom in the molecule , but also how the atoms are joined together
• full structural formula is where all the bonds in the atoms are displayed
• shortened can have the full formula condensed in one line , or shows all the carbon to carbon bonds and the branches can be clearly seen

Question 4

what is skeletal structural formula

Answer 4

• ultimate abbreviation of organic structures which uses lines to represent the carbon framework
• each line is understood to have a carbon atom at each end unless another atom such as oxyegn or nitrogen is attached
• look in notes for drawings

Question 5

skeletal structure ;
if joined to 1 branch 
2 branches 
3 branches
4 branches

Answer 5

1 branch - CH3
2 branches - CH2
3 branches - CH
4 branches - C

Question 6

three dimensional representation

Answer 6

look at bright red page 47