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CHEM191 MODULE 1 + 2 > MODULE 1 > Flashcards

MODULE 1 Flashcards

1
Q

What is a limiting reagent

A
  • The reactant which is not produced in excess
  • The reaction finishes when the limiting reagent runs out
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2
Q

What equation is used to work out grams of substance B when given grams of substance A

A
  • Mass to moles of substance A
  • use coefficients
    Then moles to mass of substance B
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3
Q

How to work out limiting reagents

A
  • Calculate moles of both reactants
  • work out which gives the smallest amount of product
  • Minus the moles limiting reagent from other reagent
    Then work out the mass of the non limiting reagent remaining in excess
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4
Q

What is a strong electrolyte

A

A solute that completely dissociates to give ions in solution
- the reactants fully turn to ions

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5
Q

What is a weak electrolyte

A

A solute that incompletely dissociates to give ions in solution
- some reactants dissolve to ions but a lot form molecules

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6
Q

What happens to the density of water as it melts

A

Becomes more dense
- water molecules spread out when frozen

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7
Q

Hydrogen bonding means that water…. And why ?

A
  • has high boiling and melting points
  • retains heat for a long period of time

Because a lot of heat energy is needed to break the hydrogen bonds, energy is released as the bonds form again making it retain heat

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8
Q

What is Kc

A

Equilibrium constant
- the ratio of products to reactants at equilibrium

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9
Q

What is Q

A

The ratio of reactants to products at any given time of the reaction

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10
Q

If Q is less than K what will happen in the reaction in terms of reactants and products

A

Reactants will be converted to products until equilibrium is reached

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11
Q

If Q is greater than K what will happen in the reaction in terms of reactants and products

A

products will be converted to reactants until equilibrium is reached

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12
Q

When calculating K, what values must you be sure you use?

A

Concentrations at EQUILIBRIUM
- use an ICE table if they are not at equilibrium

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13
Q

What will happen to the reaction if more reactants are added?

A

The forward reaction will increase, the equilibrium position will move to the right
- in attempt to make more products, bringing the reaction back to equilibrium

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14
Q

What will happen to the reaction is more products are added?

A

The rate of the backwards reaction will increase, equilibrium position will move to the left
- in attempt to make more reactants and bring the reaction back to equilibrium

  • remember K does not change
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15
Q

What is a saturated solution

A

The maximum amount of solute dissolved in a particular volume of solvent

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16
Q

How to calculate Ksp

A

sxs

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17
Q

Will a precipitate form is Qsp is less than Ksp

A

No precipitate will form

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18
Q

Will a precipitate form if Qsp is greater than Ksp

A

A precipitate will occur

19
Q

Will the presence of a common ion decrease or increase the solubility of an ionic solid

A

It will decrease the solubility

  • to solve set up an ICE table
20
Q

Brønsted-Lowry definition of an acid

A

Proton donor

21
Q

Brønsted-Lowry definition of a base

A

Proton acceptor

22
Q

How many electrons do conjugate acid base pairs differ by

A

Differ by one electron
- the acid will have one more electron than the conjugate base

23
Q

The smaller the Ka or Kb, the ……….. the acid or base

A

The smaller the Ka or Kb, the weaker the acid or base

24
Q

The smaller the pKa or pKb, the ……… the acid or base

A

The smaller the pKa or pKb, the stronger the acid or base

25
Q

What is a buffer solution

A

Made from a weak acid and a conjugate base, both at a reasonable concentration

26
Q

A buffer solution will …..

A
  • will maintain a reasonably constant pH when significant amounts of OH- or H+ ions are added
  • pH of a buffer is also unaffected by reasonable dilution of the solution
27
Q

What is buffer capacity

A

When the reaction goes to completion, meaning eventually the weak acid or its conjugate base will be used up and will no longer be a buffer solution

28
Q

What occurs at the half equivalence point on a titration curve

A

HA and A- are equal

pH = pKa

Half equivalence point = perfect buffer

29
Q

What is the equivalence point on a titration curve

A

All A-

30
Q

What is a diprotic acid

A

An acid that has two protons it can donate

  • will do so one at a time
31
Q

At which point on a titration curve of an amino acid can a zwitterion be found

A

At the equivalence point

32
Q

How many atoms are there in one mole

A

6.022x10 to power of 23

33
Q

How to convert pKa into Ka

A

Ka = 10 to the power of negative pKa

34
Q

In a saturated solution does Qsp = Ksp

A

Yes

35
Q

How to work out the solubility of something when given the concentration of a common ion

A

Ksp = s(conc of common ion)

  • if conc is greater than s you can ignore the second s and just use equation above
  • do Ksp divided by conc of common ion to find s
36
Q

How to calculate pOH

A
  • log (OH-)
37
Q

How to work out pH when given concentration of a base

A

Work out pOH
- log (OH-)

Then do 14 - the answer you got to get pH

38
Q

More than 1 pH unit above pKa, what can be said about the molecules in an ionisable functional group

A

90% of molecules are deprotonated

39
Q

More than 1 unit below pKa, what can be said about the molecules in an ionisable functional group

A

90% of molecules are protonated

40
Q

Are polar molecules hydrophilic or hydrophobic

A

Hydrophilic - water loving

41
Q

Do alcohols ionise

A

No

42
Q

What is ionisation state influence by

A
  • the pH of the aqueous environment
  • the fundamental physical property - i.e the pKa
43
Q

What is ionisation status

A

How easy it is to ionise

CHEM191 MODULE 1 + 2 (2 decks)

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