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Chemistry > Chapter 4 > Flashcards

Chapter 4 Flashcards

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1
Q

What happens when an acid dissolves in water?

A

The acid releases hydrogen ions as protons, H+ in the solution

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2
Q

What is a strong acid?

A

A strong acid release all its hydrogen atoms into the solution as H+ ions as it completely dissociates in aqueous solution.

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3
Q

Name an example of a strong acid?

A

HCl

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4
Q

What is a weak acid?

A

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

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5
Q

Give an example of a weak acid?

A

CH3COOH, ethanoic acid

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6
Q

What does the equilibrium symbol mean when representing a weak acid?

A

That the forward reaction is not complete

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7
Q

Give examples of bases?

A

Metal oxides, metal hydroxides, metal carbonates and ammonia

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8
Q

What is a base?

A

A base neutralises an acid to form a salt

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9
Q

What is an alkali?

A

It is a base which dissolves in water releasing OH- ions into the solution.

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10
Q

What is a neutralisation reaction?

A

An acid neutralises with a base, where the H+ions react with the base forming a salt and neutral water

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11
Q

Metal + acid –>

A

Salt + hydrogen

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12
Q

Metal oxide/hydroxide –>

A

Salt + water

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13
Q

Acid + Alkali –>

A

Salt + water

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14
Q

Acid + metal carbonate –>

A

Salt + water + CO2

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15
Q

What is a titration?

A

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

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16
Q

Why are titrations used?

A

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

17
Q

What is a standard solution?

A

It is a solution of a known concentration

18
Q

How do you prepare a standard solution?

A
  1. Weigh the solid
  2. The solid is dissolved using minimum distilled water needed to fill the volumetric flask to the line
  3. The solution is transferred to a volumetric flask, where the last traces are rinsed with distilled water into the volumetric flask
  4. The flask is finished off with distilled water by filling to the graduation line, this is added a drop at a time, until the bottom of the meniscus lines up with the line. If too much water is added, this has to be done again as the solution is now too dilute. The graduation and meniscus line should be viewed at eye level from accuracy.
  5. The volumetric flask is slowly inverted several times, to mix the solution throughly, if this stage is omitted the results will be inconsistent. When you invert you will see the solutions mixing together.
19
Q

What type of reaction is a acid- base titration?

A

Neutralisation reaction

20
Q

What is the burette reading always read to?

A

The nearest half division with the bottom of the meniscus on the mark. Each reading is measured to the nearest 0.05cm cubed so always has 2dp e.g 25.40 or 26.25

21
Q

Describe the acid base titration?

A
  1. Add a measured volume of one solution to a conical flask with a pipette.
  2. Add the other solution into the burette and record the initial reading to the nearest 0.05 cm3
  3. Add a few drops of indicator to the solution in the conical flask
  4. Run the solution in the burette into the solution in the conical flask, swirling the mixture throughout, in order to mix the solutions. Once the indicator has changed colour the end point has been reached, as this indicates the volume of one solution which exactly reacts with the volume of the second solution.
  5. Record the final burette reading. You now have the titre
  6. A trial run is carried out, to find an approx titre
  7. The titration is repeated accurately, adding the solution dropwise as the end point approaches. Further titrations are carried out until accurate titres are concordant ( agree within 0.1 cm3)
22
Q

What is a titre?

A

The volume of solution added from the burette, which is calculated by subtracting the initial from the final reading.

23
Q

What is a mean titre?

A

It is when the closest titres are used, you repeat the experiment until two agree within 0.1 you can reject any others.

24
Q

What are the errors of the titration?

A

An air bubbles forms inside and that the reading is taken from the top instead of the meniscus.

25
Q

How do you work out titration calculations?

A
  1. Work out the amount of solute in the solution for one, where you have both concentration and volume.
  2. Use the equation to work out the amount of the solute in the other solution
  3. Workout the unknown concentration about the solute in the other solution.
26
Q

If you get a 25.00 cm in the titration what do you do to the results?

A

You times by 10 as it goes into 250 cm cubed.

27
Q

How do you work out the identification of a carbonate?

A
  1. Calculate the amount acid reacted (use mean titre)
  2. Determine the amount of the unknown that reacted using an equation
  3. Work out the unknown info
28
Q

What is the oxidation number?

A

It is based on a set of rules which apply to atoms and can be through as the number of electrons involved in the bonding of a different element.

29
Q

What are the redox rules for elements?

A

The oxidation number is 0 as the bonding within the element is the same.

30
Q

What are the redox rules of ions and compounds?

A

Each atom in a compound has an oxidation number.

31
Q

Where does the sign for oxidation numbers?

A

Before the number

32
Q

What do the Roman numerals indicate?

A

The oxidation state of the element

33
Q

In terms of oxygen what is redox?

A

Oxidation was the addition of oxygen and reduction was the removal of oxygen.

34
Q

What has to happen in a redox reaction?

A

if one occurs so does the other

35
Q

Define Redox in terms of electrons?

A

Oxidation is loss, Reduction is gain

OILRIG

Chemistry (23 decks)

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