Thermochemistry

Question 1

Entropy increase

Answer 1

If entropy increases due to solid melting or a liquid is vaporising
This is a change from high order to low disorder of particles
State if reaction is endo or exothermic therefore then if entropy is positive or negative

Question 2

Exothermic

Answer 2

Heat energy would be released into surroundings and bonds are made

Question 3

Endothermic

Answer 3

Heat energy is brought in from surroundings being absorbed this bonds are breaking

Question 4

Attractive forces between particles

Answer 4

Talk about similar electron clouds therefore temporary dipole attractions between molecules are of similar strength. Then talk about the c=o bond as this is a permanent dipole attraction as they are polar. Then talk about hydrogen bonding due to high differences in electronegative more heat energy is required.

Question 5

2 bonded

Answer 5

Linear

Question 6

3 bonded

Answer 6

With have a base shape of a regional planar

With 2 bonded and one lone pair the shape is angular

Question 7

4

Answer 7

4 bonded is tetrahedral
Three bonded and one lone pair trigonal pyramidal
Two bonded and two lone pairs is angular

Question 8

5

Answer 8

5 bonded is a trigonal bypyramdial
4 bonded and one lone pair is a seesaw
3 bonded and two lone pairs is t shaped

Question 9

6

Answer 9

6 bonded is octahedral
5bonded one lone pair would be a square pyramidal
4 bonded and two lone pairs is a square planar

Question 10

Intermolecular attractions

Answer 10

First consider the size of the molecule if it’s larger more electrons meaning larger electron cloud therefore stronger temporary dipole attractions. Permanent and hydrogen are the strong bonds and they take more heat energy to overcome them

Question 11

Experimental value

Answer 11

It can’t be perfectly replicated as heat could of been lost into the surroundings, absorbed heat from apparatus or incomplete combustion it also couldn’t be done under standard conditions

Question 12

Fusion and Vap

Answer 12

Fusion solid to liquid only requires some intermolecular forces to be broken however vaporising requires all intermolecular forces to be overcome and more heat energy will be required

Question 13

Atomic radius

Answer 13

Decreases across a period as atomic number increases so does the positive charge in the nucleus and more protons are added, the electron shells are pulled with more force and radius decreases. As the valance shell is pulled in closer to the nucleus atomic radius will decrease

Will increase down a group as number of electrons shells increase, valance electrons further from nucleus

Question 14

Ionisation energy

Answer 14

Ionisation energy is energy needed to remove a mole of electrons from a mole of gaseous atoms from outermost electron shell
Ionisation will increase across a period as increased number of protons increasing the energy required to remove one or the electrons
Going down group will decrease due to increase of shells so valance electrons further from the protons attracting less strongly and less energy is needed to remove

Question 15

Electronegativity

Answer 15

The measure of attraction that an atom has for a pair of electrons in a chemical bond
Increases across a period and will decrease down the group. Fl is most electronegative as valance electrons are closest to the nucleus and this charge will increase.

Decrease down a group increasing the distance of bonding electrons from nucleus decreases attraction, shielding effect reduces the pull of the nucleus on bonding electron pair