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Chemistry > Topic 3 - Chemical changes > Flashcards

Topic 3 - Chemical changes Flashcards

1
Q

Common sulfates are soluble except which ones?

A

Lead sulfate, calcium sulfate, barium sulfate

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2
Q

What method could be used to prepare a sample of soluble copper sulfate from insoluble copper oxide and sulfuric acid

A

Filtration

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3
Q

What does the term dilute?

A

Low moles/mass per unit of volume in a solution

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4
Q

What colour is methyll orange in acids and alkalis?

A
  • Acid - red
  • Alkali - yellow
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5
Q

Describe the test for carbon dioxide

A
  • Bubble the gas through limewater
  • If the limewater turns cloudy, carbon dioxide is present
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6
Q

What is formed at the anode in electrolysis?

A

Anode - Oxygen or a halide (Halide only forms if you have a halide ion)

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7
Q

Common chlorides are soluble except which ones?

A

Silver chloride and lead chloride

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8
Q

When a soluble salt is prepared from an acid and an insoluble reactant, whythe solution left is only salt and water

A

As the acid is all used up and the insoluble reactant has been removed, this only leaves the salt and water.

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9
Q

What colour is phenolphthalein in acids and alkalis?

A
  • Acid - Colourless
  • Alkali - Pink
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10
Q

How does a neutralisation reaction work?

A

Hydrogen ions from the acid react with hydroxide ions from the alkali to form water

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11
Q

What happens when an acid reacts with a metal carbonate?

A

Acid + Metal Carbonate –> Salt + Water + Carbon Dioxide

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12
Q

How do you prepare a pure, dry sample of an insoluble salt?

A
  1. Mix the two solutions to form the salt
  2. Filter mixture using filter paper
  3. The residue on filter paper is insoluble salt
  4. Wash salt with distilled water and leave to dry
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13
Q

Explain the movement of ions during electrolysis

A
  • Positively charged cations migrate to negatively charged cathode
  • Negatively charged anions migrate to positively charged anode
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14
Q

Are all nitrates soluble or insoluble?

A

Soluble

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15
Q

What is reduction?

A

Gain of electrons

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16
Q

What is formed at each electrode during electrolysis of copper chloride solution?

A

Anode - Chlorine
Cathode - Copper

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17
Q

What is formed at each electrode during electrolysis of molten lead bromide?

A

Anode - Bromine
Cathode - Lead

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18
Q

What indicators can be used to measure pH?

A
  • Litmus
  • Methyl Orange
  • Phenolphthalein
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19
Q

What is electrolysis?

A

A process in which electrical energy, from a direct current supply, decomposes electrolytes

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20
Q

What is a cathode

A

Negatively charged electrode

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21
Q

What does it mean if an alkaline has a higher pH?

A

The higher the pH, the higher the concentration of hydroxide ions

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22
Q

What happens when an acid reacts with a metal hydroxide?

A

Acid + Metal Hydroxide–> Salt + Water

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23
Q

How can electrolysis of copper sulfate solution be used to purify copper

A
  • Place 2 copper electrodes into copper sulfate solution. Anode should be impure copper and cathode should be pure copper. Connect to a power supply
  • Copper in impure anode is pulled towards cathode to form pure copper. Impurities qwill form as sludge below the anode. Cu2+ ions from copper sulfate remain in solution
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24
Q

What are alkalis in relation to bases?

A

Alkalis are soluble bases

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25
What method must be used to prepare a salt from an acid and a soluble reactant? Why?
* Titration * As both reactants are soluble, titration allowd you to combine reactants excactly and avoid adding excess of either reactant as this would be hard to remove
26
What is formed at the cathode in electrolysies?
Metal (if cation is less reactive than hydrogen) or Hydrogen (if metal is more reactive than hydrogen)
27
What are cations?
Positively charged ions
28
What does it mean if an acid is weak?
It only partly dissociates into ions in aquous solutions E.g. Ethanoic acid, Citric acid
29
Where does oxidation happen?
Anode
30
What is oxidation?
Loss of electrons
31
When a soluble salt is prepared from an acid and an insoluble reactant, how and why is the excess reactant removed?
* By filtration * To leave pure solution of the salt
32
Wgat colour is red litmus paper in acids and alkalis?
* Acid - Stays red * Alkali - Turns blue
33
What is an anode
Positively charged electrode
34
How do you investigate the electrolysis of copper sulfate solution with inert electrodes and copper electrodes?
Inert electrodes: 1. Pour copper sulfate solution into beaker so it is half full 2. Place two inert graphite electrodes into beaker and attach to power supply using crocodile clips and wires 3. Fill 2 test tubes with copper sulfate solution and plave over each electrode 4. Turn on power and record any observations 5. Use glowing splint to test any gas that has collected in test tubes. Record any observations Copper electrodes: 1. Measure mass of copper electrode and attach to negative terminal of power supply. Repeat with second copper electrode attaching it to positive terminal. Record masses 1. Pour copper sulfate solution into a beaker. Place copper electrodes in the beaker. 2. Turn on power supply, make sure electrodes don't touchTurn off power after 20 mins 3. Remove each electrode washing in distilled water then propanone. 4. Leave liquid to evaporate frin electrodes before measuring mass of each one. Record results ensuring you know which electrode is which 5. Repeat steps 1-4 with fresh electrodes and copper sulfate solution. Change current using variable resistor
35
What colour is blue litmus paper in acids and alkalis?
* Acid - Turns red * Alkali - Stays blue
36
What is half equation for reaction ocurring at cathode and anode during electrolysis of copper chloride?
* Anode: 2Cl --> Cl2 + 2e * Cathode: Cu2+ + 2e --> Cu
37
What does the term concentrated mean?
High moles/mass per unit of volume in a solution
38
What hapens when an acid reacts with a metal
Acid + Metal --> Salt + Hydrogen
39
When a soluble salt is prepared from an acid and an insoluble reactant, why is excess of the reactant added?
To ensure all the acid reacts
40
What happens when an acid reacts with a metal oxide
Acid + Metal Oxide --> Salt + Water
41
What are anions?
Negatively charged ions
42
What is an electrolyte?
Ionic compounds in the molten state or dissolved in water (aqueous)
43
Where does reduction happen?
Cathode
44
What makes aqueous solutions acidic?
Hydrogen Ions (H+)
45
What is a neutralisation reaction?
A reaction between an acid and a base
46
Describe how to carry out acid-alkali titration
1. Use pipette to add measured volume of acid to conical flask then add few drops of indicator. Place on white tile 2. Fill burette with alkali, take down the initial volume 3. Add alkali to conical flask. First complete rough trial to find end point (point where indicator first changes colour) 4. Repeat adding alkali drop by drop near end point while swirling flask continuously to mix 5. Record final volume in burette 6. Repeat until you have concordant results
47
What makes aqueous solutions alkaline?
Hydroxide ions (OH-)
48
Investigate the change in pH on adding powdered calcium hydroxide or calcium oxide to a fixed volume of dilute hydrochloric acid
* Use measuring cylinder or volumetric pipette to add 25 cm^3 of dilute HCL to a beaker * Add few drops of universal indicator, compare initial colour of solution to pH colour chart and record pH or use pH probe * Add calcium hydroxide or calcium oxide to the beaker one spatula at a time whilst stirring and recording pH between additions * Stop adding calcium hydroxide/calcium oxide when pH remains constant
49
What does it mean if an acid is strong?
It completely dissociates into ions in aqueous solutions E.g. Hydrochloric acid, Nitric acid, Sulfuric acid
50
Fill in the gap: All common sodium, potassium and ammonium salts are _______
All common sodium, potassium and ammonium salts are ***soluble***
51
What happens to the concentration of hydrogen ions when the pH of a solution decreases by 1
The hydrogen ion concentration increases by a factor of 10
52
What does it mean if an acid has a lower pH?
The lower the pH, the higher concentration of hydrogen ions
53
Common carbonates and hydroxides are insoluble except which ones?
Carbonates and hydroxides of: * Sodium * Potassium * Ammonium
54
Will a percipitate form when lead reacts with sulfuric acid?
Yes, Lead Sulfate - This is because lead sulfate is insoluble
55
What is the pH range for alkalis?
8-14
56
What is formed at each electrode during electrolysis of water acidified with sulfuric acid?
Anode - Oxygen Cathode - Hydrogen
57
What is formed at each electrode during electrolysis of sodium sulfate solution?
Anode - Oxygen Cathode - Hydrogen
58
What steps are required when producing pure dry salt from acid and alkali
* Complete titration to find volume of acid that reacts exactly with set volume of alkali * Use results from titration to mix the acid and alkali in correct proportions * Evaporate water from solution leaving pure dry salt crystals
59
What pH is neutral?
7
60
Why can an electrolyte carry charge
As it is in it's molten or aqueous state, it has mobile ions which can carry charge
61
Describe the chemical test for hydrogen
* Insert a lit splint into a test tube of gas * If a 'squeaky pop' is heard, hydrogen is present
62
What is the pH range for acids?
1-6
63
What is a base?
Any substance that reacts with an acid to form a salt and water only

Chemistry (5 decks)

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