Reflection to chem test

Question 1

Formula of astatine molecule

Answer 1

At2

Question 2

Describe what you would see when sodium reacts with chlorine

Answer 2

a bright yellow light
white clouds of sodium chloride

Question 3

Which ion do all acids produce in aqueous solution?

Answer 3

H+

Question 4

calcium hydroxide + ————acid → calcium chloride + ——–

Answer 4

hydrochloric , water

Question 5

Explain why carbon nanotubes conduct electricity.

Answer 5

contain delocalised electrons
(so) electrons can move through
the structure / nanotube

Question 6

Suggest one reason why it costs less to use nanoparticles rather than fine particles in
suncreams.

Answer 6

greater surface area (to
volume ratio)

Question 7

Define mass number

Answer 7

total neutrons and protons

Question 8

Give one limitation of using a dot and cross diagram to represent an ammonia
molecule.

Answer 8

It does not show how the atoms are arranged in space.

Question 9

Evidence from the alpha particle scattering experiment led to a change in the model of
the atom from the plum pudding model.
Explain how

Answer 9

most (alpha) particles passed
(straight) through (the gold foil)

(so) most of the atom is empty
space

some (alpha) particles were
deflected / reflected

(so) the atom has a (positively)
charged nucleus / centre

Question 10

Explain why ammonia has a low boiling point.
You should refer to structure and bonding in your answer.

Answer 10

(ammonia has) weak
intermolecular bonds

little energy is needed
to break the intermolecular
bonds

(ammonia has) a simple
molecular (structure)

Question 11

Suggest two control variables used in this investigation.

Answer 11

• temperature
• concentration of electrolyte

Question 12

order reactivity
cobalt
copper
magnesium
nickel
silver
tin

Answer 12

)magnesium
cobalt
nickel
tin
copper
silver

Question 13

Justify your order of reactivity.

Answer 13

most reactive (metal)
has the highest voltage

Question 14

Which of the following pairs of metals would produce the greatest voltage when used
as the electrodes in the cell?

Answer 14

Magnesium and tin

Question 15

Hydrogen fuel cells can be used to power different forms of transport. Suggest why.

Answer 15

(in a fuel cell) hydrogen is
oxidised (to produce water)

water is produced / released as
gas / vapour / steam

Question 16

Explain why a mixture is used as the electrolyte instead of using only
aluminium oxide.

Answer 16

mixture has a lower melting
point (than aluminium oxide)
(so) less energy needed

Question 17

What happens at the negative electrode during the production of aluminium?

Answer 17

aluminium ions gain electrons

Question 18

Complete the balanced half-equation for the process at the positive electrod

Answer 18

2O2-→ O2 + 4e-

Question 19

Explain why the positive electrode must be continually replaced.

Answer 19

the electrode reacts with oxygen
the electrode is carbon /
graphite
(so) carbon dioxide is produced

Question 20

Explain why sodium chloride solution cannot be used as the electrolyte to produce
sodium metal

Answer 20

hydrogen (gas) would be
produced (instead of sodium)
(because) sodium is more
reactive than hydrogen

Question 21

Suggest one reason why step 8 is needed.

Answer 21

to make sure all of the oxide (of
copper) has reacted

Question 22

Explain why the excess hydrogen must be burned off.

Answer 22

hydrogen is explosive

Question 23

What happens at the negative electrode during the production of aluminium?

Answer 23

Aluminium atoms gain electrons

Question 24

Number of moles=

Answer 24

Mass(g)/relative atomic mass (Ar)

Question 25

What is relative atomic mass

Answer 25

Protons+neutrons

Question 26

Density (g/cm3)

Answer 26

=mass (g) /volume (cm3)

Question 27

1 cm3=

Answer 27

0.001dm3

Question 28

1000cm3

Answer 28

1dm3

Question 29

Explain why the reaction between ammonia and oxygen is exothermic.

Answer 29

the products have (kJ) less energy than the reactants
(so) energy is released (to the surroundings)