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A-Level Chemistry > 4 Acid and Redox > Flashcards

4 Acid and Redox Flashcards

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1
Q

What is a strong acid?

A

An acid that dissociates completely in solution. A strong acid such as hydrochloric acid releases all of its hydrogen atoms into solution as H+ ions.
HCl -> H+ + Cl-

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2
Q

What is a weak acid?

A

An acid that dissociates only partially in solution. A weak acid such as ethanoic acid, CH3COOH only releases a small proportion of its available hydrogen atoms into solution as H+ ions.

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3
Q

What is a base?

A

A compound that neutralises an acid to form a salt.

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4
Q

What is an alkali?

A

A type of base that dissolves in water forming hydroxide ions, OH- ions.
NaOH -> Na+ (aq) + OH- (aq)

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5
Q

What are some examples of bases?

A

Metal oxides, metal hydroxides, metal carbonates and ammonia

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6
Q

What happens during neutralisation?

A
  • In neutralisation of an acid, H+ (aq) ions react with a base to form a salt and neutral water.
  • The H+ ions from the acid are replaced by metal or ammonium ions from the base.
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7
Q

What is the formula for sulfuric acid?

A

H2SO4

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8
Q

What is the formula for sodium sulfate?

A

Na2SO4

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9
Q

What is the formula for nitric acid?

A

HNO3

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10
Q

What is the formula for calcium nitrate?

A

Ca(NO3)2

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11
Q

What is the formula for ethanoic acid?

A

CH3COOH

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12
Q

What is the formula for ammonium ethanoate?

A

CH3COONH4

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13
Q

What is the word equation for neutralisation?

A

Acid + alkali -> salt + water

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14
Q

What is the ionic equation for neutralisation?

A

H+ (aq) + OH- (aq) -> H2O (l)

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15
Q

What is produced when carbonates neutralise acids?

A

Salt, water and carbon dioxide gas.

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16
Q

What is a titration?

A

A titration is a technique used to accurately measure the volume of one solution that reacts exactly with another solution.

17
Q

What can titrations can be used for?

A
  • Finding the concentration of a solution
  • Identification of unknown chemicals
  • Finding the purity of a substance
18
Q

What is a standard solution?

A

A solution of known concentration.

19
Q

What is the uncertainty of volumetric flasks?

A
  • 100cm^3 volumetric flask: +-0.20cm^3

- 250cm^3 volumetric flask: +-0.30cm^3

20
Q

How do you prepare standard solutions?

A

1) Using a weighing boat, accurately weigh 2.10g of solid sodium hydrogencarbonate.
2) Transfer the solid to a dry, clean 100cm^3 beaker. Rinse the weighing boat with distilled water into the beaker.
3) Add enough distilled water to dissolve the solid, stirring with a glass rod.
3) Transfer the solution to a 250cm^3 volumetric flask. The last traces of the solution are rinsed into the flask with distilled water.
4) The flask is carefully filled to the graduation line by adding distilled water a drop at a time until the bottom of the meniscus lines up exactly with the mark.
5) Finally, the volumetric flask is slowly inverted several times to mix the solution thoroughly.

21
Q

How do you work out the mean titre?

A
  • It’s important to use only your closest accurate titres.

- By repeating titres until two agree within 0.10cm^3, you can reject inaccurate titres.

22
Q

What is the uncertainty of a 10cm^3 pipette?

A

+- 0.04cm^3

23
Q

What is the uncertainty of a 25cm^3 pipette?

A

+- 0.06cm^3

24
Q

What is the uncertainty of a 50cm^3 burette?

A

+- 0.10cm^3

25
Q

What is the acid-base titration procedure?

A

1) Use a pipette filler to transfer 25cm^3 of your standard solution to a 250cm^3 conical flask.
2) Add 50cm^3 of hydrochloric acid to a burette, and record the initial burette reading to the nearest 0.05cm^3.
3) Add a few drops of methyl orange indicator to the solution in the conical flask.
4) Titre the sodium hydrogencarbonate solution with the hydrochloric acid, with constant swirling, until the end point is reached (yellow or orange). This is your trial titration.
5) The titration is then repeated accurately, adding the hydrochloric acid dropwise as the end point is approached. Further titrations are carried out until two accurate titres are concordant- agreeing to within 0.10cm^3.

26
Q

What is the oxidation number?

A

A measure of the number of electrons that an atom uses to bond with atoms of another elements.

27
Q

What is the oxidation number for oxygen?

A

-2

28
Q

What is the oxidation number for hydrogen?

A

+1

29
Q

What is the oxidation number for fluorine?

A

-1

30
Q

What is the oxidation number for Na+ and K+?

A

+1

31
Q

What is the oxidation number for Mg2+ and Ca2+?

A

+2

32
Q

What is the oxidation number for Cl-, Br- and I-?

A

-1

33
Q

What is the oxidation number of H in metal hydrides?

A

-1

34
Q

What is the oxidation number of O in peroxides?

A

-1

35
Q

What is the oxidation number when O is bonded to F?

A

+2

36
Q

What are redox reactions in terms of oxygen?

A
  • Oxidation is the addition of oxygen.

- Reduction is the removal of oxygen.

37
Q

What are redox reactions in terms of electrons?

A
  • Reduction is the gain of electrons.

- Oxidation is the loss of electrons.

38
Q

What is redox in terms of oxidation number?

A
  • Reduction is a decrease in oxidation number.

- Oxidation is an increase in oxidation number.

A-Level Chemistry (27 decks)

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