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Titrations and analysis Flashcards

1
Q

What is the formula to calculate moles?

A

Moles = Concentration x volume (dm³)

Volume should be in cubic decimeters (dm³) for this formula.

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2
Q

How do you convert volume from dm³ to cm³?

A

Divide by 1000

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3
Q

What is the formula to convert concentration from mol/dm³ to g/dm³?

A

Multiply by the Mr

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4
Q

What is the formula to calculate moles from mass?

A

Moles = mass / Mr

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5
Q

What are the three main steps in concentration calculations?

A
  • Find the moles of the substance
  • Look at the ratios in the equation
  • Unmole it by dividing by concentration or volume
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6
Q

What is a titration used for?

A

To find out how much acid is needed to neutralise a volume of alkali or vice versa

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7
Q

What is required to find the concentration of an unknown acid or alkali in a titration?

A

You must know the concentration of the other substance

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8
Q

What type of reactions do titrations typically involve?

A

Reactions between strong acids and strong bases

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9
Q

What is the first step in the titration method?

A

Wash out the burette and the pipette with the solutions

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10
Q

What should you do after placing acid or alkali in the burette?

A

Fill the burette until the acid is in line with 0 cm

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11
Q

How do you measure a known volume of alkali or acid for titration?

A

Use a volumetric pipette

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12
Q

What indicator is mentioned for use in titrations?

A

Methyl Orange

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13
Q

Why is a white tile used during a titration?

A

To help see the colour change better

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14
Q

What should you do as you approach the end point of a titration?

A

Add the contents of the burette drop by drop

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15
Q

What should you record from the burette during a titration?

A

Initial and final volume readings

Take all readings from the bottom of the meniscus.

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16
Q

What is the purpose of performing a rough titration?

A

To get an approximate idea of when the end point is.

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17
Q

How do you obtain concordant results in titration?

A

Repeat an accurate titration until you get concordant results.

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18
Q

What should you do with your results to determine the final volume needed for neutralization?

A

Take the mean average of your results, excluding any anomalies.

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19
Q

What is the function of a burette in titration?

A

Dispense a variable amount of acid/alkali and accurately measure how much is dispensed.

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20
Q

What is the role of a volumetric pipette in titration?

A

Measure a fixed portion of alkali or acid added to the conical flask.

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21
Q

What is the purpose of the conical flask in a titration?

A

Hold the solution from the pipette and the indicator.

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22
Q

Why is a white tile used during titration?

A

To allow easy detection of color change.

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23
Q

What color does methyl orange turn in alkali?

A

Yellow.

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24
Q

What color does phenolphthalein turn in alkali?

A

Pink.

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25
Why can't universal indicator be used in titration?
The color change is too gradual/not sharp.
26
What is the uncertainty for a single measurement?
+ or - half the smallest scale of division.
27
How is uncertainty represented for a range of measurements?
+ or - the range.
28
How can uncertainties be represented on graphs?
By plotting vertical lines joining repeat readings for each independent variable value.
29
What happens when you hold a lit splint to hydrogen?
It burns with a squeaky pop.
30
What occurs when you hold a glowing splint in oxygen?
It relights with a glowing splint.
31
What happens when you bubble carbon dioxide through limewater?
A white precipitate forms ## Footnote This is a test for the presence of carbon dioxide.
32
How can you test for chlorine gas?
Hold damp litmus paper over the sample; it will bleach the litmus paper white ## Footnote This indicates the presence of chlorine.
33
What is the first step in conducting a flame test?
Clean a nichrome wire in dilute HCl and hold it over a Bunsen burner until it burns without colour ## Footnote This ensures no contamination affects the test results.
34
What color flame does lithium ions produce in a flame test?
Crimson flame ## Footnote This is a characteristic color for lithium ions.
35
What color flame does sodium ions produce in a flame test?
Yellow flame ## Footnote This is a distinctive color for sodium ions.
36
What color flame does potassium ions produce in a flame test?
Lilac flame ## Footnote This is the specific color associated with potassium ions.
37
What color flame does calcium ions produce in a flame test?
Orange-red flame ## Footnote This is the unique flame color for calcium ions.
38
What color flame does copper ions produce in a flame test?
Green flame ## Footnote This indicates the presence of copper ions.
39
What can affect the visibility of flame test colors?
Mixture of ions ## Footnote Some flame colors may be hidden by others if multiple ions are present.
40
What is the procedure when sodium hydroxide (NaOH) is added to a solution containing unknown ions?
Add a few drops of NaOH and record the color of the precipitate ## Footnote This helps identify the positive ions present in the solution.
41
What color precipitate do iron (II) ions form when treated with NaOH?
Green precipitate ## Footnote This indicates the presence of iron (II) ions.
42
What color precipitate do iron (III) ions form when treated with NaOH?
Brown precipitate ## Footnote This is a characteristic result for iron (III) ions.
43
What color precipitate do copper (II) ions form when treated with NaOH?
Blue precipitate ## Footnote This indicates the presence of copper (II) ions.
44
What happens to the precipitate formed by aluminum ions when excess NaOH is added?
White precipitate dissolves to form a colorless solution ## Footnote This behavior helps differentiate aluminum ions from others.
45
What color precipitate do calcium ions form when treated with NaOH?
White precipitate which persists in excess NaOH ## Footnote This indicates the presence of calcium ions.
46
What color precipitate do magnesium ions form when treated with NaOH?
White precipitate which persists in excess NaOH ## Footnote This helps confirm the presence of magnesium ions.
47
What is the method to test for carbonates?
Add dilute acid (e.g., HCl) to the sample and bubble the products into limewater ## Footnote This test indicates the presence of carbonates if a white precipitate forms in limewater.
48
What occurs when carbonate ions (CO3^2-) are treated with dilute acid?
Effervescence occurs and a white precipitate forms when bubbled through limewater. ## Footnote This is due to the release of carbon dioxide gas.
49
What is the chemical reaction for sodium carbonate reacting with hydrochloric acid?
Sodium Carbonate + Hydrochloric acid → sodium chloride + Water + Carbon Dioxide ## Footnote This reaction illustrates the formation of products from carbonate ions.
50
How can sulfate ions (SO4^2-) be detected?
By adding HCl or nitric acid followed by barium chloride solution, resulting in a white precipitate. ## Footnote A positive result confirms the presence of sulfate ions.
51
What is the procedure to test for halides?
Add dilute nitric acid followed by silver nitrate solution. ## Footnote This helps to identify chloride, bromide, and iodide ions based on the color of the precipitate.
52
What color precipitate forms for chloride ions in the halide test?
White precipitate forms. ## Footnote This indicates the presence of chloride ions.
53
What color precipitate indicates the presence of bromide ions?
Cream precipitate forms. ## Footnote This is a specific indicator for bromide ions.
54
What color precipitate indicates the presence of iodide ions?
Yellow precipitate forms. ## Footnote This is a specific indicator for iodide ions.
55
Why is an acid added before testing for halides?
To remove impurities such as carbonates by reacting with them. ## Footnote This ensures accurate test results.
56
What is a critical consideration when selecting an acid for halide tests?
The acid used should not contain chloride ions, as it would interfere with the results. ## Footnote Using hydrochloric acid would cause a false positive for chloride ions.
57
What must be remembered when forming ionic equations?
Ions can only be split up if they are aqueous. ## Footnote This is important for correctly representing the reactions in ionic form.
58
What are the pros of using instrumental methods for detection?
Very accurate, sensitive, and rapid. ## Footnote These advantages make instrumental methods favorable for analysis.
59
What are the cons of using instrumental methods?
Expensive, can only compare to known substances, requires specialised training. ## Footnote These limitations can restrict the use of instrumental methods.
60
What is an example of an instrumental method used for analysis?
Flame emission spectroscopy. ## Footnote This method analyzes metal ions in solutions using a flame photometer.
61
How does flame emission spectroscopy work?
The sample is put into a flame, and the light emitted is passed through a spectroscope to produce a line spectrum diagram. ## Footnote This spectrum can be compared to known diagrams for element identification.

Chemistry (16 decks)

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