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Y4 Chem > Chem pracx > Flashcards

Chem pracx Flashcards

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1
Q

Indicators

A

Screened Methyl Orange
red, grey, green (3-5)

Thymol Blue
red, green blue (8-10)

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2
Q

Which only reacts with concentrated base

A

Silicon dioxide

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3
Q

Metal oxides are

A

Basic
Amphoteric (Zinc, Aluminium, Lead)

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4
Q

Non-metal oxides are

A

Acidic
Neutral (Water, Carbon monoxide, Nitrogen monoxide)

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5
Q

Solubility table

A

Sulfate: BP CA (sparing)
Halides: Silver, Lead (II)
Oxides: CaO (sparing)
Hydroxides: Calcium and Barium both sparingly

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6
Q

How to prepare insoluble salt

A

Precipitation
1. Mix the solutions to produce a precipitate
2. Filter the mixture to obtain a residue
3. Wash the residue with a small amount of distilled water to remove any impurities
4. Dry the precipitate between a few sheets of filter paper

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7
Q

Why cannot use precipitation for soluble salt

A

Difficult to determine endpoint and will produce an impure salt

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8
Q

Insoluble salt prep option 1

A

Insoluble solid-Acid reaction
- Add solid in excess (metal, carbonate base)

  1. Add ____ a little at a time to hot ____ while stirring
  2. Filter the mixture to obtain the filtrate
  3. Heat the filtrate gently till saturation
  4. Allow the solution to cool for crystal to form
  5. Filter the mixture to remove excess water
  6. Wash the crystals with a small amount of distilled water to remove impurities
  7. Dry the crystals between sheets of filter paper
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9
Q

Why need to add solid in excess for solid-acid reaction

A

To ensure the reaction is complete and all the soluble reactant is used up (to prevent contamination)

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10
Q

Titration to obtain what salts

A

SPA salts
(can use alkali or carbonate)

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11
Q

Titration steps

A
  1. Fill up a 50cm3 burette with _______ of unknown concentration
  2. Pipette 25cm3 of ________ into a 250cm3 conical flask and add 2 drops of ______ indicator
  3. Titrate _____ against ________
  4. Record the volume of _______ used when the indicator first turns ______ in a single drop
  5. Repeat the titration till consistent results are obtained
  6. Calculate the average volume of _____ used from the 2 best readings
  7. Repeat the titration with the calculated volume of _____ without the indicator
  8. Heat the solution till saturation
  9. Allow the solution to cool for crystals to form
  10. Filter the mixture to remove excess _____
  11. Wash the crystals with a small amount of distilled water
  12. Dry the crystals between a few sheets of filter paper
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12
Q

Base + Ammonium salt

A

Ammonia + Salt + Water

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13
Q

Strongest oxidising agent

A

Fluorine (Group 7)

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14
Q

Strongest reducing agent

A

Lithium (Group 1)

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15
Q

Test for reducing agent

A

Acidified potassium manganate VII (purple to colourless)

Iodine (brown to colourless)

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16
Q

Test for oxidising agent

A

Potassium iodide (colourless to brown)

17
Q

More reactive metal stronger or weaker ____ agent

A

Stronger reducing agent

18
Q

Carbon vs Hydrogen _____ agent

A

Carbon stronger reducing agent

19
Q

Reactivity table

A

Please Stop Calling Me A Careless Zebra, (HYDROGEN) Instead Try Learning How Copper Saves Gold Platinum

20
Q

Methods to prevent rusting

A
  1. Protective layer
  2. Galvanising
  3. Sacrificial protection
  4. Alloys
21
Q

Rusting formula

A

Iron + Oxygen + Water –> Hydrated iron III oxide

4Fe + 3O2 + 2xH2O –> 2Fe2O3.xH2O

22
Q

Acid-Alkali reaction (pH)

A

Use pH meter to measure rate of change in pH

23
Q

Colour change

A

Use a colorimeter to measure the change in intensity of colour

24
Q

Production of ppt

A
  1. Conductivity meter to measure the change in concentration of mobile ions over time (electrical conductivity)
    1. Mark a thick big cross in pencil on a piece of white paper
  3. Stand a 100cm3 beaker over the cross on the paper
  4. (do the experiment)
  5. Observe the cross by looking vertically down through the solution from above the beaker. Record the time taken to the nearest seconds when the cross just disappears completely
  6. Work out the reciprocal of the time for the cross to disappear. This is proportional to the average rate of reaction during that interval of time

cannot determine instantaneous

25
Q

Gas collection

A
  1. Assemble gas collection apparatus as shown in the diagram below
  2. Carefully but quickly add the zinc to the nitric acid in the flask and start the stop watch at the same time
  3. Stop the stopwatch when 15cm3 of ____ has been collected in the gas syringe
26
Q

Pressure (equilibrium)

A

Shift to side with more moles to increase pressure
Shift to side with less moles to decrease pressure

26
Q

Concentration (equilibrium)

A

When increase conc on left, move right (remove)
When decrease on left, move left (produce more)

27
Q

Temperature (equilibrium)

A

Move towards exo reaction to release heat
Move towards endo reaction to absorb extra heat

28
Q

Catalyst (equilibrium)

A

Achieve equilibrium at a faster rate

Y4 Chem (10 decks)

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