Reactions of acids

What is a base?

a substance with a ph greater than 7

What is an alkali?

A base that dissolves in water to form a solution with a pH greater than 7

What is an acid?

a substance that forms aqueous solution with a pH of less than 7.

What does an acid form in water?

H+ ions

What does an alkali form in water?

OH- ions

What is a neutralisation reaction and what does it form?

The reaction between acids and bases.

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Acid + base → salt + water

eg

H+ + OH- → H2O

what salt does hydrochloric acid produce?

Chloride

What salt does nitric acid produce?

Nitrate

What salt does sulfuric acid produce?

sulfate

How to make soluble salts? (summary from spec)

soluble salts can be made from acids by reacting them with solid insoluble substances, such as metals, metal oxides, hydroxides, or carbonates.

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The solid is added to the acid until no more reacts and the excess solid is filtered off to produce solution of the salt.

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Salt solutions can be crystallised to produce solid salts.

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How to make soluble salts dry and full sample? (full method)

1\.       Measure 40 cm3 sulfuric acid into the 100 cm3 beaker. 

 

2\.       Set up the tripod, gauze and heatproof mat.  Heat the acid gently using the Bunsen burner until it is almost boiling.  Turn off the Bunsen burner.

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3\.       Use the spatula to add small amounts of copper (II) oxide powder.  Stir with the glass rod.  



Continue to add copper (II) oxide if it keeps disappearing when stirred.  When the copper (II) oxide disappears the solution is clear blue.

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4\.       Stop adding the copper (II) oxide when some of it remains after stirring.  



Allow apparatus to cool completely.

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5\.       Set up the filter funnel and paper over the conical flask.  Use the clamp stand to hold the funnel. 



Filter the contents of the beaker from step 3.

 

6\.       When filtration is complete, pour the contents of the conical flask into the evaporating basin. 



Evaporate this gently using a water bath (250 cm3 beaker with boiling water) on the tripod and gauze (see diagram).  Stop heating once crystals start to form. 



7\.       Transfer the remaining solution to the crystallising dish.  Leave this in a cool place for at least 24 hours.



8\.       Remove the crystals from the concentrated solution with a spatula. Gently pat the crystals dry between two pieces of filter paper. 



These are pure dry crystals of copper (II) sulfate.

What is a strong acid ? provide examples

ionise completely in water. strong acid is completely ionised in aqueous solution. All acid particles dissociate to release H+ ions.

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Hydrochloric, nitric and sulfuric acid.

What is a weak acid? provide examples

A weak acid is only partially ionised in aqueous solutions.

only a small proportions release H+ ions.

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Ethanoic, citric and carbonic acids.

What happens to the rate of reaction with the concentration of H+ ions?

If the concentration of H+ ions is higher, the rate of reaction will be faster, so strong acids will me more reactive than weak acids of the same concentration.

The relationship between pH and hydrogen ion concentration in a solution.

As the pH decreases by one unit, the hydrogen ion concentration of the solution increases by a factor of 10.

Ph of a concentrated acid

pH will decrease with increasing acid concentration regardless of whether it’s a strong or weak acid

what does the strength of an acid mean?

Acid strength tells you what proportion of the acid molecules ionise in water.

(the number of molecules ionised to produce hydrogen ions at any given amount)

What is the concentration

how much acid there is in a certain volume of water.

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(larger amount of acid in a certain volume, the more concentrated the acid is)

{how watered down your acid is}

What is the difference in pH between a *weak* acid and a *strong* acid of the same concentration ?

   The pH of a strong acid is lower than the pH of a weak acid; 

Explanation:

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* Strong acids dissociate completely in aqueous solutions; 
* Weak acids only partially dissociate; 
* Therefore, weak acids produce fewer H+ ions in solution than strong acids;
* Because a lower number of acid molecules dissociate;