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PPE Flashcard for Checklist > Chemistry > Flashcards

Chemistry Flashcards

1
Q

Why does a chemical cell eventually stop producing a voltage?

A

Eventually, one of the reactants is used up so the reaction stops and a voltage is no longer produced.

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2
Q

Describe the main features of a hydrogen-oxygen fuel cell

A

A hydrogen-oxygen fuel cell contains two platinum electrodes which catalyse the formation of hydrogen ions and electrons from hydrogen gas.

There is also a membrane, which lets the hydrogen ions pass but not the electrons.

The electrons flow through the external circuit, connected to an electric motor.

At the right hand electrode, hydrogen gains electrons and reacts with the oxygen coming in. Water is a waste product.

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3
Q

What is electroplating?

A

This is when electricity is used to coat one metal with a thin layer of another

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4
Q

Give some examples of electroplating

A
  • Producing jewelry that has gold/silver electroplated onto cheaper ‘‘base metals’’.
  • To improve a metal’s ability to resist corrosion e.g electroplating with chromium, which resists corrosion.
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5
Q

How is electroplating carried out?

A

Electrolysis set up:

  • anode, made from the plating metal
  • cathode - metal object itself
  • electrolyte - containing ions of the plating metal
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6
Q

What is an isotope?

A

Atoms of the same element with the same number of protons but different mass numbers due to different numbers of neutrons.

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7
Q

What does group number tell us about electronic configuration?

A

It tells us the amount of electrons in the outer shell

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8
Q

What does the period tell us about electronic configuration?

A

It tells us how many electron shells there are

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9
Q

What substances are generally soluble in water?

A
  • All nitrates
  • All sodium, potassium and ammonium salts
  • Most chlorides
  • Most sulfates
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10
Q

What substances are insoluble in water?

A
  • Most hydroxides
  • Most carbonates
  • Silver, lead chloride
  • Calcium, barium, lead sulfates
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11
Q

How can we predict whether a precipitate is formed in a reaction?

A

We can view the products, if one product is insoluble then a precipitate is formed

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12
Q

Describe the movement of ions during electrolysis

A

Positive ions (cations) will be attracted to the negative electrode (cathode)

Negative ions (anions) will be attracted to the positive electrode (anode)

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13
Q

What is meant by theoretical yield?

A

The maximum mass of product that can be formed from a given amount of reactants

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14
Q

What is actual yield?

A

The actual amount of product produced when an experiment is carried out

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15
Q

How do you calculate percentage yield?

A

Actual / Theoretical X 100

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16
Q

Explain 3 reasons why actual yield is lower than theoretical yield

A

1) Some product may be lost - for example when transferring containers, some liquid may be left behind
2) The reaction may be incomplete - not all the reactants have reacted yet
3) There may be side reactions occurring - which competes with the main reaction, producing different products

17
Q

How do you calculate atom economy?

A

(Sum of Mr of useful products / Sum of Mr of reactants) X 100

18
Q

How do we use atom economy and yield to determine reaction pathway?

A

We want a reaction pathway that produces a higher yield as this will allow for higher profit since more product is being made in a given time.

Atom economy means the process is more efficient, so there will be less wasted molecules.

19
Q

When should we use fractional distillation when separating a mixture?

A

If there is a small difference in the boiling points of the liquids

20
Q

Describe some physical properties of transition metals

A
  • Malleable
  • Ductile
  • Good conductors of electricity
  • Shiny when polished
21
Q

Describe some chemical properties of transition metals

A
  • Form coloured compounds

- Can act as catalyst

22
Q

Describe the two biological methods of extraction

A

Bioleaching - This is where bacteria are grown on a low grade ore. This produces a solution containing copper ions, called a leachate. Copper can be extracted from the leachate by displacement, then purified by electrolysis

Phytoextraction - this is where plants that absorb metal compounds are grown. Then, they are burnt to form ash from which we extract the metal.

23
Q

Describe how to carry out fractional distillation

A

A column is fixed above the distillation flask.

We heat the solution, then hot vapour rises up the column. At first, the vapour condenses when it hits the glass and drips back down into the flask.

As the column heats up gradually, a temperature gradient is created, warmer at the bottom, cooler as you go up.

The fraction with the lowest boiling point will reach the top of the column first, it will then pass through the condenser and the distillate is collected in a flask.

24
Q

What happens in a reversible reactions?

A

The products react to reform the reactants

25
Q

What is meant by dynamic equilibrium?

A

Dynamic equilibrium is when, in a reversible reaction, forward and backward reactions are occurring at the same rate so the concentration of the reactants and products stay constant.

26
Q

What is meant by the mole of particles?

A

A mole of a substance is 6x10^23 of it.

27
Q

How do you calculate mols?

A

Mass / Ar

28
Q

How do you calculate the number of particles in a given number of moles?

A

Number of Moles x Avogadro’s Constant

29
Q

Describe the formation of ammonia

A

N2 + 3H2 -> 2NH3

30
Q

State conditions for the Haber Process

A
  • 450 degrees
  • 200atm
  • Iron catalyst
31
Q

Describe how changing temperature, press and concentration affect amount of substances in an equilibrium mixtuer

A

Increasing temperature shifts the reaction in the endothermic direction

Increasing pressure shifts the reaction to the side with fewer mols

Increasing concentration shifts to the side that uses up the substance added

32
Q

Describe what oxidation and reduction mean in terms of:

1) electrons
2) oxygen

A

1) Oxidation means loss of electrons, reduction means gain of electrons
2) Oxidation means gain of oxygen, reduction means loss of oxygen

33
Q

How do you calculate concentration?

A

MASS / VOLUME

g/dm3

34
Q

How do you convert g/dm3 into mol/dm3?

A

g/dm3 / Mr = Mol/dm3

35
Q

What is meant by the molar volume of a gas?

A

1 mol of any gas occupies 24 dm3 volume at room temperature and pressure

36
Q

What is Avogadro’s law?

A

If room temperature and pressure are the same, equal volumes of different gases contain an equal number of molecules

PPE Flashcard for Checklist (3 decks)

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