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Chemistry > Chapter 4 > Flashcards

Chapter 4 Flashcards

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1
Q

Formula of hydrochloric acid

A

HCl

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2
Q

Formula of sulphuric acid

A

H2SO4

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3
Q

Formula of nitric acid

A

HNO3

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4
Q

Formula of ethanoic acid

A

CH3COOH

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5
Q

Formula of sodium hydroxide

A

NaOH

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6
Q

Formula of potassium hydroxide

A

KOH

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7
Q

Formula of ammonia

A

NH3

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8
Q

What is an acid?

A

An acid is a substance that will release H+ ions when in an aqueous solution

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8
Q

What is an alkali?

A

An alkali is a soluble base and will release OH- ions in an aqueous solution

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9
Q

What is a base?

A

Bases are compounds that neutralise acids but do not dissolve, by accepting a hydrogen ion to form a salt

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10
Q

What is the definition of a strong acid?

A

A strong acid is an acid that releases all its hydrogen atoms as H+ ions and completely dissociates in aqueous solutions

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11
Q

What is the definition of a weak acid?

A

A weak acid is an acid that only releases a small proportion of its available hydrogen atoms into the solution as H+ ions. A weak acid partially dissociates in an aqueous solution.

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12
Q

Examples of a strong acid:

A

HCl
H2SO4
H3PO4

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13
Q

Examples of a weak acid

A

CH3COOH

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14
Q

What is the ionic equation for neutralisation by an alkali including state symbols?

A

H+(aq) + OH-(aq) –> H2O(l)

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15
Q

What is produced when an acid is neutralised with a metal oxide/hydroxide?

A

An acid is neutralised by a metal oxide/hydroxide to form a salt and water only.

CuO(s) + H2SO4 (aq) –> CuSO4 (aq) + H2O(l)

16
Q

What is produced when an acid is neutralised by an alkali?

A

An acid is neutralised by an alkali to form a salt and water only.

Full equation: HCl(aq) + NaOH(aq) –> NaCl(aq) + H2 (l)

Ionic equation: H+(aq) + OH-(aq) –> H2O(l)

17
Q

What is produced when an acid is neutralised with a carbonate?

A

An acid is neutralised by a carbonate to form a salt, water and carbon dioxide.

ZnCO3(s) + H2SO4(aq) –> ZnSO4(aq) + H2O(l) + CO2(g)

18
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 to find an unknown concentration.

19
Q

What can a titration be used for?

A

Finding the concentration of a solution
Identification of unknown chemicals
Finding the purity of a substance

20
Q

What is a standard solution?

A

A solution of known concentration

21
Q

What is used to make up a standard solution very accurately?

A

A volumetric flask

22
Q

Method to preparing a standard solution:

A
  1. The solid is first weighed accurately
  2. The solid is then dissolved in a beaker using less distilled water than will be needed to fill the volumetric flask to the mark.
  3. This solution is then transferred to a volumetric flask. The last traces of the solution are rinsed into the flask with distilled water.
  4. The flask is filled to the graduation line by adding distilled water a drop at a time until the bottom of the meniscus lines up.
  5. Finally the volumetric flask is slowly inverted several times to mix the solution thoroughly.
23
Q

What things are done to ensure an accurate solution when preparing a standard solution?

A

The graduation mark and meniscus must be viewed at eye level
Volumetric flask must be used
Consistent results are found from inverting the volumetric flask several times

24
Q

What equipment is used in an acid-base titration?

A

Burette, pipette, conical flask

25
Q

What actions are taken to ensure an accurate titration?

A

When filling a burette, excess solution is run out through the tap to remove any air bubbles.
Burette readings must be taken from the bottom of the meniscus from eye level

26
Q

Method of an acid-base titration:

A
  1. Add a measured volume of one solution to a conical flask using a pipette
  2. Add the other solution to the burette, and record the initial burette reading
  3. Add a few drops of a single indicator into the conical flask
  4. Run the solution in the burette into the solution into the conical flask, swirling the conical flask throughout to mix the two solutions. Eventually, the indicator changes colour at the endpoint of the titration.
  5. Record the final burette reading. This is known as the titre and is worked out by doing final reading - initial reading.
  6. The first result is used as a rough titre in order to calculate the approximate titre
  7. The titration is then repeated accurately, adding the solution dropwise as the endpoint is approached. Further repeats are done until two concordant results are achieved.
27
Q

What is an oxidation number?

A

It can be thought of as the number of electrons involved in bonding to a different element.

28
Q

Oxidation number rules for elements

A

The oxidation number is always 0 for elements

29
Q

Oxidation number rules for compounds

A

Each atom in a compound has an oxidation number which typically sum to 0 (if a neutral compound)

30
Q

Oxidation number rules for ions

A

The oxidation number of an ion of an element is numerically the same as the charge of the ion

31
Q

How is the oxidation number of hydrogen special?

A

The oxidation number of hydrogen is usually +1, however if the hydrogen is part of a metal hydride (e.g. NaH), then the oxidation number becomes -1.

32
Q

How is the oxidation number of oxygen special?

A

The oxidation number of oxygen is usually -2, however if if it is part of a peroxide (H2O2) then the oxidation number becomes -1.
If the oxygen is bonded to fluorine (F2O), then the oxidation number is +2.

33
Q

What is the oxidation number of sulphur in sulphuric acid, H2SO4? (worked example)

A
  1. Assign the oxidation numbers to the separate elements: Total H = +1x2 = +2 Total O = -2x4 = -8
  2. Let the oxidation number of S be X, and form an equation:
    +2 + X + (-8) = 0
  3. Rearrange for X:
    X = +8-2
    X= +6

So the oxidation number of S, in H2SO4 is +6

34
Q

What is the oxidation number of nitrogen in NO3-?

A
  1. Assign the oxidation numbers to the separate elements: Total O = -2x3 = -6
  2. Let the oxidation number of N be X, and form an equation:
    X + (-6) = -1
  3. Rearrange for X:
    X = -1+6
    X = +5

So the oxidation number of N in NO3- is +5

35
Q

Use of Roman numerals and oxidation number:

A

The Roman numeral shows the oxidation number of an element when it may have different oxidation numbers. The sign of the oxidation number can be worked out from the overall charge of the compound.

Iron (II) represents Fe2+ with oxidation number +2
Iron (III) represents Fe3+ with oxidation number +3

36
Q

What is oxidation?

A

Oxidation is the loss of electrons and the gain in oxygen.
Oxidation is also an increase in oxidation number

37
Q

What is reduction?

A

Reduction is the gain of electrons and the loss of oxygen. Reduction is also a decrease in oxidation number.

Chemistry (20 decks)

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