Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Advanced chemistry > Researching Chemistry > Flashcards

Researching Chemistry Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

What is back titration?

A

When an excess reagent is added to an analyte and then titrated with a second reagent.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is precipitation?

A

When a reagent is reacted with a solution to form a precipitate, the precipitate is separated from the filtrate and tested to ensure the reaction has gone to completion. It is then washed, dried to constant mass and weighed. The accuracy of this method relies on the accuracy of the balance used.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is volatilisation?

A

Heating substances to evaporate off any volatile products. The substance is heated to constant mass and the final mass is recorded

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a desiccator used for?

A

Used to create a ‘dry’ environment where samples can cool without absorbing water, it does NOT remove water from samples.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do you heat until constant mass?

A

Accurately weigh the sample, heat sample in crucible to eliminate any volatile products, cool sample in a desiccator to prevent water reabsorbing, reweigh the sample, repeat from heating the sample, and then repeat until the mass is constant.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why do impurities form during synthesis reactions?

A

Due to impure reactants, side reactions and incomplete reactions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the equivalence point of a reaction?

A

The point at which the reaction is just complete.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a back titration also known as?

A

An indirect titration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is a suitable control during a redox titration?

A

Carrying out the titration using a known concentration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is distillation?

A

It is the separating of liquids which have different boiling points and is used for the identification and purification of organic compounds. It can also be used to purify a compound by separating it from less volatile substances within the mixture.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does distillation rely on?

A

It relies on the the difference in boiling points of the compounds in the mixture.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

When will a reaction be carried out under reflux?

A

If any of the reactants or products are volatile and either the reaction is exothermic or the reaction requires heating.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

In precipitation reactions what does reacting two soluble reagent solutions form?

A

An insoluble salt.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why is vacuum filtration used over gravity filtration and what is used?

A

Because it is faster, a Buchner or Hirsch funnel is used.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is re-crystallisation used for?

A

Used to PURIFY impure solids.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How is re-crystallisation carried out?

A

An IMPURE solid is dissolved in hot solvent, HOT filtration is carried out to remove INSOLUBLE impurities, the filtrate is cooled down slowly to allow crystals of the pure compound to form and then filtering, washing and drying the pure crystals.

17
Q

What must the solvent chosen for re-crystallisation be able to do and why is it chosen?

A

Must be able to dissolve the compound at HIGH temperatures. Chosen so that the compound being purified is completely soluble at high temperatures and only sparingly at lower temperatures

18
Q

When carrying out solvent extraction, what happens?

A

The two immiscible solvents form layers in the separating funnel. The solute dissolves in both solvents and an equilibrium establishes between the two layers. The lower layer is run off into a container and the upper layer is poured into a second container. This is then repeated to maximise the quantity of solute extracted.

19
Q

What does solvent extraction involve?

A

Isolating a solute from a solution by extraction using an immiscible solvent in which the solute is soluble.

20
Q

What equipment is used in solvent extraction?

A

A separating funnel is used to separate/ extract two immiscible solvents from each other.

21
Q

What is gravimetric analysis?

A

It is used to determine the mass of an element or compound in a substance. The substance is then converted into another substance of known chemical composition, which can be readily isolated or purified- the conversion can occur via precipitation or volatilisation.

22
Q

What is a solution of accurately known concentration known as?

A

A standard solution.

23
Q

How can a standard solution be prepared?

A

Weighing a primary standard accurately, dissolving in a small volume of solvent in a beaker, transferring the solution and rinsing’s into a volumetric flask, making up to the graduation mark with solvent and then finally stoppering and inverting.

24
Q

Properties of standard solutions are?

A

They must be available in a high state of purity, be stable when solid and in solution, be soluble and have a reasonably high GFM.

25
Q

What are examples of primary standards?

A

Sodium Carbonate- Na2CO3
Hydrated Oxalic Acid- H2C2O4·2H2O
Silver Nitrate- AgNO3
Potassium Iodate- KIO3
Potassium Dichromate- K2Cr2O7

26
Q

Why is sodium hydroxide not a primary standard?

A

It has a relatively low GFM, is unstable as a solid and as a solution. Sodium hydroxide solution must be standardised before being used in volumetric analysis.

27
Q

What is EDTA?

A

It is an important complexometric reagent and can be used to determine the concentration of metal ions in solutions. It complexes one mole of free metal ions in complexiometric titrations and one mole of EDTA: 1 mole of free metal ions.

28
Q

What is a colorimeter/ spectrophotometer used for?

A

To measure the absorbance of light of a series of standard solutions.

29
Q

How is the concentration of the solution being tested determined?

A

From it’s absorbance and by referring to the calibration curve.

30
Q

What must lie on the straight line section of a calibration graph?

A

The concentration of coloured species in a solution being tested.

31
Q

What is one physical property that can confirm the identity of a compound?

A

Boiling point.

32
Q

What is the percentage yield decreased by?

A

Mass transfer or mechanical losses, purification of products, side reactions and the equilibrium position.

33
Q

What does the unit PPM stand for?

A

Parts Per Million and refers to 1 mg per kg or 1 mg per litre.

34
Q

What is percentage by mass?

A

It is the mass of SOLUTE made up to 100 cm3 of solution.

35
Q

What is percentage by volume?

A

It is the number of cm3 of solute made up to 100 cm3 of solution.

Advanced chemistry (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions