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Flashcards in C5 - Quantitative Analysis Deck (44)
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31

Why is a vanadium pentoxide catalyst used in the contact process?

The vanadium pentoxide catalyst increases the rate of reaction but does not affect the position of the equilibrium.

32

Why is atmospheric pressure used?

1. There are fewer moles of products, so increasing the temperature will move the equilibrium to the right.

2. However, increasing the pressure is very expensive and the equilibrium already lies toward the right.

3. Therefore, it is not really necessary to increase the pressure. 

4. Therefore, atmospheric pressure used.

33

Name a weak acid.

Ethanoic acid

34

Name three strong acids.

Sulfuric acid

Nitric acid

Hydrochloric acid

35

Why is the pH of a weak acid much higher than the pH of a strong acid of the same concentration.

The strong acid fully ionises in water, meaning it will have a greater concentration of H+ ions. On the other hand, weaker acid only partially ionise and will therefore have a smaller concentration of H+ ions.

36

What is acid strength?

The degree of ionsation of the acid.

For example, strong acids fully ionise and release lots of H+ ions. Weak acids only partially ionise and release fewer H- ions.

37

What is the equation for the ionisation of hydrochloric acid (a strong acid)?

HCl ---> H+ Cl-

38

What is the equation for the partial ionisation of ethanoic acid (a weak acid)?

CH3COOH ⇌ H+ CH3COO-

39

Why does ethanoic acid react slower than hydrochloric acid of the same concentration?

- Ethanoic has a lower concentration of hydrogen ions.

- Therefore, there is a lower collision frequency between the hydrogen ions and the reactant particles.

40

Explain why ethanoic acid is less conductive than hydrochloric acid of the same concentration

There is a lower concentration of hydrogen ions available to carry the charge in ethanoic aicd.

41

Why does the electrolysis of hydrochloric acid or ethanoic acid produce hydrogen?

They both contain H+ ions that gain electrons to form H2 gas.

42

Why are most precipitation reactions extremely fast?

Precipitation reacts are usually very fast because of the high collision frequency between the ions.

43

What are spectator ions?

In a precipitation reaction, the spectator ions are the ions which do not change in the reaction (they remain in the solution, they don't form the precipitate).

44

What are the three stages involved to prepare a dry sample of an insoluble compound?

1. Solutions of reactants mixed.

2. Filitration

3. Wash and dry residue