Reflection to chem test Flashcards

1
Q

Formula of astatine molecule

A

At2

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2
Q

Describe what you would see when sodium reacts with chlorine

A

a bright yellow light
white clouds of sodium chloride

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3
Q

Which ion do all acids produce in aqueous solution?

A

H+

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4
Q

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

A

hydrochloric , water

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5
Q

Explain why carbon nanotubes conduct electricity.

A

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

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6
Q

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

A

greater surface area (to
volume ratio)

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7
Q

Define mass number

A

total neutrons and protons

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8
Q

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

A

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

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9
Q

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

A

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

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10
Q

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

A

(ammonia has) weak
intermolecular bonds

little energy is needed
to break the intermolecular
bonds

(ammonia has) a simple
molecular (structure)

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11
Q

Suggest two control variables used in this investigation.

A
  • temperature
  • concentration of electrolyte
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12
Q

order reactivity
cobalt
copper
magnesium
nickel
silver
tin

A

)magnesium
cobalt
nickel
tin
copper
silver

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13
Q

Justify your order of reactivity.

A

most reactive (metal)
has the highest voltage

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14
Q

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

A

Magnesium and tin

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15
Q

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

A

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

water is produced / released as
gas / vapour / steam

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16
Q

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

A

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

17
Q

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

A

aluminium ions gain electrons

18
Q

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

A

2O2-→ O2 + 4e-

19
Q

Explain why the positive electrode must be continually replaced.

A

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

20
Q

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

A

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

21
Q

Suggest one reason why step 8 is needed.

A

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

22
Q

Explain why the excess hydrogen must be burned off.

A

hydrogen is explosive

23
Q

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

A

Aluminium atoms gain electrons

24
Q

Number of moles=

A

Mass(g)/relative atomic mass (Ar)

25
What is relative atomic mass
Protons+neutrons
26
Density (g/cm3)
=mass (g) /volume (cm3)
27
1 cm3=
0.001dm3
28
1000cm3
1dm3
29
Explain why the reaction between ammonia and oxygen is exothermic.
the products have (kJ) less energy than the reactants (so) energy is released (to the surroundings)