Topic 3a Flashcards
Done except for a few specpoints
3.1
What ion do acids produce an excess of when dissolved in water?
Hydrogen ions
H+
3.1
What ion do alkalis produce an excess of when dissolved in water?
Hydroxide ions
OH-
Define an ion
An atom that has lost or gained electrons
Define a poly-atomic ion
Groups of atoms held by covalent bonds lose/gain electrons
3.1
Explain why the pH of hydrogen bromide becomes acidic when dissolved in water?
H+ ions form making it acidic
3.2
a) A neutral solution has a pH of…?
b) Acidic solutions have a pH of…?
c) Alkali solutions have a pH of…?
a) 7
b)1-6
c) 8-14
What is an advantage to having internationally agreed hazard symbols?
Anyone can understand them and stay safe
What is the main advantage to using a pH probe?
Measurements are accurate
3.4
The most acidic rain recorded in Britain had a pH of 2. How much more acidic is this than normal rainwater with a pH of 5. [2 marks]
10 × 10 × 10 =
×1000 more H+ ions
3.5
Describe the relationship between the pH and the concentration of hydrogen ions
As the pH decreases by 1, the concentration of H+ ions increases by a factor of 10
3.5
Describe the relationship between the pH and the concentration of hydroxide ions
As the pH increases by 1, the concentration of OH- ions increases by a factor of 10
3.7
Explain the term dilute
Contains relatively small volume of dissolved solute
3.7
Define the term concentrated
Contains relatively large amount of dissolved solute
3.8
What is a strong acid?
-Completely dissociates to form H+ ions in solution
-High concentration of H+ ions
3.8
What is a weak acid?
-Partially dissociates to form H+ ions in solution
-Low conc H+ ions
3.10
What are alkalis?
-Soluble bases
-pH greater than 7
3.9
What is a base?
Neutralise acids to form salt + water
I find an unmarked bottle and want to work out if the liquid inside is acidic or not. How could I do this?
Universal indicator
If it’s red/orange/yellow it’s an acid
Why are metal oxides bases?
They neutralise acids
3.11
State 4 reaction equations of aqueous solutions of acids that produce salts
Metal + Acid –> Salt + Hydrogen
Metal oxide + Acid –> Salt + Water
Metal hydroxide * + Acid –> Salt + Water
Metal carbonate + Acid –> Salt + Carbon dioxide + Water
Acid + Alkali –> Salt + Water
Typically alkalis *
3.11
What salt will hydrochloric acid form?
Chloride
3.11
Which salt will sulfuric acid form?
Sulfate
3.11
Which salt will nitric acid form?
Nitrate
3.11
Finish the equations:
a) Zinc oxide + Sulfuric acid –>
b) Sodium oxide + Hydrochloric acid—>
Zinc sulfate + Water
Sodium chloride + Water
3.11
What happens to the ions from acids and alkali during a neutralisation reaction?
H+ ion from acid combines with OH- ion from alkali to form water
Name 3 common acids
Hydrochloric acid - HCl
Sulfuric acid - H₂SO₄
Nitric acid - HNO₃
Name 3 common alkalis
Sodium hydroxide - NaOH
Potassium hydroxide - KOH
Calcium hydroxide - Ca(OH)₂
Name 3 polyatomic ions
Hydroxide - OH^-
Carbonate - CO₃²^-
Nitrate - NO₃^-
What is the ionic formula for sodium?
Na(+)
What is the ionic formula for lithium?
Li(+)
What is the ionic formula for potassium?
K(+)
What is the ionic formula for magnesium?
Mg(2+)
What is the ionic formula for calcium?
Ca(2+)
What is the ionic formula for aluminium?
Al(3+)
What is the ionic formula for fluoride?
F(-)
What is the ionic formula for chloride?
Cl(-)
What is the ionic formula for bromide?
Br(-)
What is the ionic formula for oxygen?
O(2-)
What is the ionic formula for sulfide?
S(2-)
What is the ionic formula for nitrate?
NO₃(-)
What is the ionic formula for sulfate?
SO₄(2-)
What is the ionic formula for carbonate?
CO₃(2-)
What is an independent variable?
One you change
What is a dependent variable?
One that you measure
What is a control variable?
One that stays the same
3.6
What are the independent, dependent and control variables in neutralisation?
Independent - calcium hydroxide m in solution
Dependent - pH of reaction mixture
Control
- v of HCl added each t
-Conc of HCl
3.6
Neutralisation
How can you increase the accuracy of your results?
-Measure calcium hydroxide m w/ balance
-Measure pH w/ pH probe rather than estimate w/ universal indicator
3.6
Neutralisation
Describe what happens to the pH of the solution as the mass of calcium hydroxide added increases?
pH increases (directly proportional)
3.6
What is the ionic equation for neutralisation?
H+(aq) + OH-(aq) –> H₂O(l)
3.6
Describe 3 risks that could take place in a neutralisation reaction and how they can be managed
-Calcium hydroxide = irritant (goggles)
-HCl = irritant (goggles)
-Solution spill (wipe)
What is a salt?
Reaction between acid + base (in neutralisation reaction)
3.12
Describe the chemical test for hydrogen
-Place lit splint into test tube
-Burns to produce squeaky pop
3.12
Describe the chemical test for carbon dioxide
-Pass/bubble the gas through lime water
-Lime water turns milky/cloudy
3.12
Describe the chemical test for chlorine gas
-Damp blue litmus paper
-Turns red
-Then bleached
3.13
What is a neutralisation reaction?
Between acid & base
3.14
Describe what happens in a neutralisation reaction
H^+ ions from acid react w/ OH^- ions from alkali to form water
~3.17
Describe how to prepare an insoluble salt
-Mix soluble salts in water
-Filter -> remove precipitate
-Rinse precipitate w/ distilled water -> remove traces of solution
-Dry by heating in oven
3.19
Recall the general solubility rules of common substances in water
SOLUBLE
-Sodium, potassium, ammonium carbonates, hydroxides and salts
-All nitrates
-Most chlorides
-Most sulfates
INSOLUBLE
-Most carbonates & hydroxides
-Silver & lead chloride
-Lead, barium & calcium sulfate
3.19
Using the solubility rules identify whether each of these substance are soluble or insoluble
a) Sodium chloride
b) Silver chloride
c) Silver nitrate
d) Calcium carbonate
a) Soluble
b) Not soluble
c) Soluble
d) Not soluble
3.20
What happens during a precipitation reaction?
Soluble substance in solution forms insoluble precipitate
3.20
Name the precipitate formed when solutions of the following compounds are mixed together
a) Sodium hydroxide & barium chloride
b) Silver nitrate & potassium chloride
a) Sodium chloride (aq) + BARIUM HYDROXIDE (s)
b) SILVER CHLORIDE (s) + Potassium nitrate (aq)
(Note: precipitate is in capitals bc I put all the products & precipitate is insoluble one)
~3.21
Describe how to prepare a soluble salt
-Add excess base to ensure all acid used up
-Heat mixture in water bath (speed reaction)
-Filter to ensure prepared salt = pure
-Heat -> crystallise salt solution
-Leave to slowly evaporate -> bigger crystals
3.17
Explain how to prepare a pure dry sample of copper sulfate
-Fixed v dilute sulfuric acid
-Warm acid in water bath
-Small amounts of copper oxide to acid (stir)
-Copper oxide reacts -> dissolves
-Continue adding until powder = excess (no longer reacts)
-Filter mixture
-Transfer solution -> evaporating basin
-Heat (evaporating basin over beaker of water heated w/ Bb until crystals start to form)
-Pour solution in watch glass for copper sulfate crystals to form (for a few days)
-Pat dry
3.18
Describe the process of titration
-Clean pipette w/ water, rinse w/ sodium hydroxide solution
-Clean burette w/ water, rinse w/ dilute HCl
-Use pipette to transfer 25cm^3 sodium hydroxide solution into conical flask
-Few drops of acid-base indicator
-Fill burette w/ dilute HCl & take reading
-Add HCl from burette to alkali in conical flask, swirling contents at all times
-Add acid drop-by-drop near end-point until colour changes
-Take final burette reading
3.18
Suggest why universal indicator is not used in titration
-No sharp colour change
-Methyl orange/phenolphthalein used instead
-Bc have only 2 colour change
3.18
Titration
Why should you clean the pipette and burette with water before carrying out titration?
Reduce contamination to not interfere with results
3.18
Titration
What is the purpose of using a pipette to transfer the sodium hydroxide?
To accurately measure solution
3.18
Titration
Why do we only add a few drops of acid-base indicator to the alkali solution in the conical flask?
-Indicator=slightly acidic
-If add too much, will interfere with results
3.18
Titration
Why is a conical flask used to contain the alkali?
Allows swirling w/o spilling
3.18
Titration
Why should you continuously swirl the contents?
-To mix thoroughly
-For reaction to occur
3.18
Titration
Why is the acid added drop-by-drop near the end-point?
To not overshoot endpoint
3.18
Titration
Why is a white tile used?
Enables indicator colour change to be seen more clearly
Describe how to prepare a pure, dry salt from an acid and an alkali
-Acid + alkali -> salt + water
-Crystallise salt by heating to evaporate water
-Pat salt dry
