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Chemistry > Chemical Changes > Flashcards

Chemical Changes Flashcards

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1
Q

describe how metals react with oxygen and state the compound they form

A

many metals react with oxygen through oxidation to make metal oxides

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2
Q

define oxidation

A

the gain of oxygen, or loss of electrons, by a substance during a chemical reaction

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3
Q

define reduction

A

the loss of oxygen, gain of electrons, or gain of hydrogen by a substance during a chemical reaction

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4
Q

list the reactivity series from most reactive to least reactive

A
  1. Potassium
  2. Sodium
  3. Lithium
  4. Calcium
  5. Magnesium
  6. Aluminium
  7. Carbon
  8. Zinc
  9. Iron
  10. Tin
  11. Lead
  12. Hydrogen
  13. Copper
  14. Silver
  15. Gold
  16. Potassium
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5
Q

how are metals above carbon in the reactivity series extracted?

A
  • electrolisis because carbon is less reactive so they can’t be displaced with carbon
  • found in ores (metals containing compound in rock= metal oxides)
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6
Q

how are metals below carbon and above hydrogen in the reactivity series extracted?

A
  • reduction with carbon because carbon is more reactive
  • metal oxide is reduced to form a metal and carbon is oxidised to form carbon dioxide
  • displacement of the metal, removes oxygen from the oxide, leaving the metal
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7
Q

how are metals below hydrogen in the reactivity series extracted?

A
  • they aren’t because they are found native as pure metals
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8
Q

recall and describe the reactions of potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper with water or dilute acids

A
  • all react with dilute acid except copper whereas magnesium, zinc and iron react less violently
  • acid + metal = salt + hydrogen
  • reaction gives off bubbles
  • potassium, sodium, lithium, calcium and magnesium react with water (p, s and l react more violently) whereas zinc, iron and copper don’t
  • metal + water = metal hydroxide + hydrogen
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9
Q

what is the link between reactivity and tendency to form positive ions

A
  • the most reactive metals have the greatest tendency to lose electrons to form positively charged ions
  • (greater tendency of getting oxidised/ losing electrons)
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10
Q

how can metals be extracted from their compounds by reduction with carbon?

A

the carbon displaces the metal from the compound, and removes the oxygen from the oxide, this leaves the metal

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11
Q

what reaction happens betweenmetals and acids in terms of gain or loss of electrons

A

redox,

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12
Q

what 3 things can acids be neutralised by?

A

alkalis, bases and metal carbonates

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13
Q

what are the products of the reactions in neutralisation of acids with alkalis, bases and metal carbonates

A
  • alkalis- salt and water
  • bases- salt and water
  • metal carbonates- salt, water and carbon dioxide
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14
Q

predict the salt produced in neutralisation of acids with alkalis, bases and metal carbonates

A
  • alkalis- Acid + alkali → salt (alkali 1 acid- ate/ ide)+ water
  • e.g. Nitric acid + sodium hydroxide → sodium nitrate + water
  • bases (metal oxides)- Acid + metal oxide → salt (metal acid- ate/ ide) + water
  • e.g. Sulfuric acid + copper oxide → copper sulfate + water
  • metal carbonates- Acid + metal carbonate → salt (metal acid-ate/ ide)+ water + carbon dioxide
  • e.g. Hydrochloric acid + copper carbonate → copper chloride + water + carbon dioxide
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15
Q

what charges do ions of each group have?

A
  • group 1- +1
  • group 2- +2
  • (group 3- +3)
  • (group 4- +4 or -4)
  • (group 5- -3)
  • group 6- -2
  • group 7- -1
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16
Q

how can soluble salts be made from acids and how to obtain pure, dry samples of salt

A
  • a soluble salt can be prepared by reacting an acid with a suitable insoluble reactant
  • pure, dry samples are obtained by crystallisation where the solution is heated to evaporate off the water leaving behind the pure, dry crystals of the salt
17
Q

define acid and alkali in terms of what ions they produce in solution

A
  • acids produce hydrogen ions, H+ in aqueous solution
  • alkalis produce hydroxide ions, OH- in aqueous solution
18
Q

define base

A

any substance that reacts with an acid to neutralise it to produce a salt and water only

19
Q

how is universal indicator used to measure the approximate pH of a solution?

A

If universal indicator is added to a solution it changes to a colour that shows the pH of the solution according to the pH scale

20
Q

what happens in a reaction between acids and some metals electron wise and what type of reaction is it?

A
  • redox reaction
  • the metal will lose electrons, becoming oxidised into a positive ion
  • hydrogen is reduced as they gain electrons
21
Q

how do you write displacement reactions as ionic redox reactions?

A
  1. get rid of any substances that appear on both sides of the equation that don’t take part in the reaction (doesn’t change)
  2. write an equation for each element (one will be reduced, one will be oxidised)
  3. you can do this by writing the symbols for the element on both sides like how they are in the equation except the two different elements are in different equations
  4. add the right amount of electrons to each side to balance the equations
  5. identify which is reduced and which is oxidised
22
Q

how do you calculate the quantities in titrations involving concentrations in mol/ dm3 and g/ dm3

A
  1. calculate the amount of solution in moles by converting the voume to dm3 (if its in cm3) (divide by 1000) and then multiply it by the concentration (moles= conc x vol)
  2. find the amount (moles) of the unknown substance by using the ratio in the balanced equation
  3. calculate the volume of the unknown substance using vol= moles/ conc
23
Q

what equation links moles, concentration and volume?

A

concentration in mol/ dm3 or g/ dm3= amount of solute in mol or g/ volume in dm3

24
Q

how do you convert between mol/ dm3 and g/ dm3?

A
  • to convert from mol/dm3 to g/dm3, multiply by the relative formula mass of the solute
  • to convert from g/dm3 to mol/dm3, divide by the relative formula mass of the solute
25
Q

what is a solute?

A

The substance that has been dissolved

26
Q

explain weak and strong in terms of the degree of ionisation in relation to acids

A
  • strong acids ionise completely meaning they completely dissociate into ions in solution
  • weak acids only partially ionise meaning they only partially dissociate in solution
27
Q

how is pH related to hydrogen ion concentration of a solution?

A
  • the pH of a solution is a measure of its concentration of hydrogen ions
  • the higher the concentration of H+ ions in an acidic solution, the lower the pH
  • the lower the concentration of H+ ions in an acidic solution, the higher the pH
    This means that, for a given concentration in aqueous solution, the stronger an acid, the lower the pH.
28
Q

how do ionic compounds conduct electricity when dissolved in water and what is this called?

A
  • ionic compounds that conduct electricity when dissolved in water are electrolytes
  • when molten or dissolved in water, the ions in electrolytes are free to move within the liquid or solution
29
Q

what is electrolysis and describe the process

A
  • the decomposition (breakdown) of a compound using an electric current
  • electrolysis is a process in which electrical energy, from a
    direct current (dc) supply, breaks down electrolytes.
  • the free moving ions in electrolytes are attracted to the oppositely charged electrodes which connect to the dc supply.
30
Q

describe the electrolysis of molten ionic compounds including how to predict the products at each electrode

A
  • they’re always broken up into their elements
  • positive metal ions are reduced at the negative electrode
  • negative non-metal ions are oxidised at the positive electrode
31
Q

use the reactivity series to explain why some metals are extracted with electrolysis instead of carbon

A

because they are more reactive than carbon so cannot be displaced (reduced) by carbon

32
Q

describe the electrolysis of aqueous solutions including how to predict the products

A

there are H+ and OH- ions too so…
* at the negative electrode: if H+ ions and metal ions are present- hydrogen is produced if the metal ion forms a metal more reactive than hydrogen
* if the metal ions form a metal less reactive than hydrogen: pure metal is produced
* at the positive electrode: if OH- and halide ions (CL-, Br-, I-) are present- chlorine, bromine or iodine is formed
* if no halide ions are presents, OH- ions and oxygen and water will be formed

Chemistry (18 decks)

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