Acids Flashcards
Which ions make aqueous solutions acidic?
Hydrogen ions (H^+)
Which ions make aqueous solutions alkaline?
Hydroxide ions (OH^-)
What is the pH scale?
The pH scale ranges from pH 0 to pH 14
and measures the acidity or alkalinity of
a solution.
What are pH ranges for acids and alkalis? What the
pH of a neutral solution?
Acid - Less than pH 7 (pH 1 is strongest).
Neutral - pH 7.
Alkali - Greater than pH 7 (pH 14 is strongest).
What can be used to measure pH?
Universal indicator
pH probe
What colour is phenolphthalein in acid, neutral and alkali?
Acid - Colourless
Neutral- colourless
Alkali - Pink
What colour is methyl orange in an acid, neutral and an
alkali?
Acid - Red
Neutral- Yellow
Alkali - Yellow
What colour is blue litmus paper in an acid and an
alkali?
Acid - Turns red
Alkali - Stays blue
What colour is red litmus paper in an
acid and an alkali?
Acid - Stays red
Alkali - Turns blue
Suggest a problem with using universal indicator to
test the pH of a solution
The colour of the solution is matched to a pH
colour chart. This is quite subjective as people
may disagree with which colour the solution
matches.
It doesn’t provide an exact pH value.
Acid X has a pH of 1. What can you say about the
concentration of hydrogen ions in acid X?
There is a high concentration of hydrogen
ions in the acid, making it a strong acid.
The lower the pH of the acid, the higher the
concentration of H^+
ions.
Alkali Y has a pH of 8.5. What can you say about the
concentration of hydroxide ions in alkali Y?
There is a low concentration of hydroxide ions in
the alkali, making it a weak alkali.
The lower the pH of the alkali, the lower the
concentration of OH^- ions.
If pH decreases by one unit, what happens to the
concentration hydrogen ions?
The hydrogen ion concentration
increases by a factor of 10.
What is a neutralisation reaction?
During an acid-alkali neutralisation reaction, what happens?
A neutralisation reaction is a reaction between an
acid and a base.
In an acid-alkali neutralisation reaction, H+
ions from the acid react with OH- ions from the alkali
to form water.
What is the ionic equation for a neutralisation
reaction?
H+ (aq) + OH^- (aq) → H2O(l)
check google if unsure
What do the terms concentrated and dilute mean
when talking about acid? Is this the same as strong/
weak acids?
Concentrated acids have more moles of acid per unit
volume of water than dilute acids.
The concentration of an acid is not the same as strength.
Strength refers to whether the acid has completely
dissociates in water or not.
An acid only partially dissociates in water. What can
be said about the strength of the acid?
Weak acid
What is a base?
Any substance that reacts with an acid to
form salt and water only.
True or false?
‘Alkalis are insoluble bases’
FALSE
Alkalis are soluble bases.
What are the products when an acid reacts with a
metal?
Salt and hydrogen
acid + metal → salt + hydrogen
What are the products when an acid reacts with a
metal oxide?
Salt and water
acid + metal oxide → salt + water
What are the products when an acid reacts with a
metal hydroxide?
Salt and water
acid + metal hydroxide → salt + water
What are the products when an acid reacts with a
metal carbonate?
Salt, water and carbon dioxide
Acid + metal carbonate→ salt + water + carbon
dioxide
Why are metal oxides normally bases rather than
alkalis?
Metal oxides are normally insoluble.
Alkalis are soluble.
What is the name of the salt formed from
magnesium and sulfuric acid?
Magnesium sulfate
What is the name of the salt formed from zinc oxide
and nitric acid?
Zinc nitrate
What is the name of the salt formed from calcium
carbonate and hydrochloric acid?
Calcium chloride
Describe the chemical test for hydrogen
Insert a lit splint into a test tube of gas.
A‘squeaky pop’ will be heard if hydrogen
is present.
Describe the chemical test for carbon dioxide
Bubble the gas through limewater
(calcium hydroxide).
Limewater turns cloudy if carbon dioxide
is present.
When a soluble salt is prepared from an acid and an
insoluble reactant, why is excess of the insoluble
reactant added?
To ensure all the acid reacts.
When a soluble salt is prepared from an acid and an
insoluble reactant, how and why is the excess
reactant removed?
By filtration.
It is removed to leave a pure solution of the
salt.
What method must be used to prepare a salt from an
acid and a soluble reactant? Why?
Titration
This is used to prepare a salt from an acid and a soluble reactant. Since both the reactants are soluble, a titration
allows you to combine the reactants exactly
and avoid adding an excess of either reactant
as this would be hard to remove.
Name the method that could be used to prepare a
sample of soluble copper sulfate from insoluble
copper oxide and sulfuric acid?
Filtration
What 3 steps are required when producing a pure
dry salt from an acid and alkali?
Complete a titration to find the volume of acid that reacts
exactly with a set volume of alkali.
Use the results from the titration to mix the acid and alkali in
the correct proportions.
Evaporate the water from the solution, leaving pure dry salt
crystals.
Describe how to carry out an acid-alkali titration
- Use a pipette to add a measured volume of acid to the conical flask
- Then add a few drops of indicator.
- Place on a white tile.
- Fill the burette with the alkali
- Note the initial volume.
- Add the alkali to the conical flask.
- First complete a rough trial to find the end point (the point at which the indicator first changes colour).
- Repeat, adding the alkali drop by drop near the end point and swirling the flask constantly to mix.
- Record the final volume in the burette. Repeat until you have concordant results.
Most common chlorides are soluble.
What are the two exceptions?
Silver chloride and lead chloride are
insoluble.
True or false?
‘All nitrates are soluble’
TRUE
Fill in the gap: ‘All common sodium, potassium and
ammonium salts are _____ ’
Soluble
Most common sulfates are soluble. What are the
three exceptions?
Lead sulfate, calcium sulfate and barium
sulfate are insoluble
Most common carbonates and hydroxides are
insoluble. What are the three exceptions?
The carbonate / hydroxides of sodium
potassium and ammonium are soluble.
What salt is produced when lead reacts with sulfuric
acid? Will a precipitate form?
Lead sulfate
A precipitate will form because lead
sulfate is insoluble.
How could you prepare a pure, dry sample of an insoluble salt?
- Mix the two solutions required to form the salt.
- Filter the mixture using filter paper.
- The residue on the filter paper is the insoluble
salt. - Wash the salt with distilled water and leave to dry.
What is the chemical symbol for hydrochloric acid?
HCl
What is the chemical notation for sodium hydroxide?
NaOH
What colour is litmus paper in a neutral solution?
Purple
What is the formula of sulfuric acid
H2SO4
What is the formula of Nitric Acid
HNO3
When an acid is in solution, a higher concentration of ___ ions means that the solution is more _____, thus having a ______ pH
H+
acidic
Lower
When an _____ is in a solution, a higher concentration of OH- ions means that the solution is more ______, thus having a ______ pH
alkali
alkaline
higher
What is dissassociation?
Dissociation is where an acid breaks down to release H+ ions in solution
Stronger an acid, greater the dissociation, the more H+ ions released, the lower
the pH
Give some examples of strong acids?
hydrochloric, nitric and sulfuric acids
Give some examples of weak acids?
ethanoic, citric and carbonic acids
acid + base → ______ + _____
Salt + water
What is the IUPAC rules for naming salts?
1) Metal e.g. Lithium
2) Acid e.g. Sulfate
How do you make an insoluble salt?
Soluble salt + Soluble salt —> Insoluble salt + Soluble salt
