Acids And Alkalis Flashcards
What can some acids and alkalis be?
Toxic or harmful to the environment
How are hazards associated with handling particular solutions?
Identified by international symbols, and they indicate the precautions that need to be taken when handling them
What is the acidity or alkalinity of a solution measured on?
Measured on the PH scale
What are solutions with a pH of 7?
Neutral
What are acids?
Solutions that have a pH lower than 7
What are solutions with a pH higher than 7?
Alkalis
The lower the pH the more acidic the solution
The higher the pH the more alkaline the solution
How can you find the pH of a solution ?
Using indicators
What is universal indicator?
A mixture of different indicators and produces a range of colours depending on the pH
In alkaline solutions what colour does litmus, methyl orange, and phenolphthalein turn?
Blue, yellow and pink
In acidic solutions what colour does litmus, methyl orange, and phenolphthalein turn?
Red, red and colourless
Acids and alkalis are always found in which state symbol So?
(Aq) aqueous because water is the base
Which range of numbers will you find on the pH scale?
0-14
How do colours of universal indicator reflect the pH numbers?
They reflect the pH numbers because the solution turns a specific colour depending on the pH number (so how acidic or alkaline a solution is
Explain how litmus paper, methyl orange and phenolphthalein are affected by acids and alkalis
This is affected by the acids and alkalis, because they turn the solution different colours depending wether it is an acid or an alkali
List 3 common acids
Hydrochloric acid - HCl
Sulphuric acid - H2SO4
Nitric acid HNO3
Numbers are all small
List 3 common alkalis
Sodium hydroxide NaOH
Potassium hydroxide KOH
Calcium hydroxide Ca(OH)2 Number is small
Acids and alkalis can be defined in terms of the ions they produce. Which ions are these?
Acids - H➕ ions
Alkalis - OH- ions
In terms of hydrogen ions, how does their concentration affect the pH?
The more H➕ ions, the more acidic the solution
In terms of hydroxide ions, how does their concentration affect the pH?
The more OH- ions, the more alkaline the solution
How is concentration calculated?
Amount dissolved ➗ volume of solution
Units: trams per decimetre cubed , gdm to the power of -3
What is the difference, in terms on concentration of H➕ ions, between a pH 3 and 5?
100 H➕ ions (each pH is x10)
Complete the sentence: strong acids …………… completely in water while weak acids ……….
Dissociate, don’t
What are all aqueous solutions?
Either acidic, alkaline or neutral
Explain why a strong acid could have the same pH as a weak acid
If the strong acid is dilute and the weak acid is concentrated, it just depends on the amount of H➕ ions
What is a base?
Bases are substances that neutralise acids to form a form a salt and water only
What is the general reaction for a metal oxide and an acid?
(Metal) salt ➕ water
How do we name the salts formed from reactions with the 3 most common acids used?
Chloride
Nitrate
Sulphate
List the steps in making a soluble salt from a neutralisation reaction
Go to page 57 in the text book and look ,
Explain why the base is added in excess, the acid is warmed and the excess is filtered
The base is added in excess so it will all react with the acid and there will be none left
The acid is warmed so the reaction will happen faster
The excess is filtered so it’s just a clear liquid solution
What is the difference between a base and an alkali?
Many bases are insoluble ( but they can be soluble) alkalis are soluble, and bases that are soluble are alkalis
How are group 1 hydroxides different to most metal oxides?
Group 1 hydroxides have 1- charge, but group 2 has a 2➕ charge and etc
What is the ionic equation that explains why a neutral solution is formed when an acid and an alkali neutralise each other
H➕(aq) ➕ OH-(aq) ➡️ H2O(l)
Why do we use a titration so to form a dry soluble salt?
Easy, reliable way, gets good crystals
List the steps in carrying out such a reaction (titration)
Add excess oxide to acid
Warm up solution to speed up reaction
Filter to remove the unreacted solid from the solution
Heat up to evaporate water and concentrate salt solution
Leave water to evaporate slowly and for crystallisation to occur
What is the general equation for the reaction between metals and acids? Give an example
Metal ➕ acid ➡️ metal salt ➕ hydrogen
Lithium ➕ hydrochloric acid ➡️ lithium chloride ➕ hydrogen
2Li ➕ 2HCl ➡️ 2LiCl ➕H2
What is a spectator ion?
Ions that don’t change during a reaction
In terms of half equations, what happens to the H➕ ions! Show the equation
The hydrogen ions gain electrons to form hydrogen molecules
2H➕ (aq) ➕ 2e ➡️ H2(g)
In terms of half equations, what happens to the metal ions? Give an example
Mg(s) ➡️ Mg2➕(aq) ➕ 2e
The magnesium atoms lose 2 electrons. A loss of electrons is an oxidation reaction. A gain of electrons is a reduction
Describe the test for hydrogen gas?
You put hydrogen gas and cotton wool in the bottom of a tube, then put a lit splint in the, if the gas is present it will pop
What is the general equation for the reaction between acids and metal carbonates? Give an example
Metal carbonate ➕ acid ➡️ metal salt ➕ water ➕ Carbon dioxide
CuCO3(s) ➕ H2SO4 ➡️ CuSO4(aq) ➕ H2O(l) ➕ CO2(g)
Describe the test for carbon dioxide gas?
Bubble it through limewater, it will turn limewater from clear and colourless to milky
What is a precipitate?
An insoluble product formed when solutions of the two soluble reactants are mixed
Write a list of the compound that are insoluble in water
Most carbonates - silver carbonate, barium carbonate
Most hydroxides - ion hydroxide, zinc hydroxide
Describe the steps in the preparation of insoluble salts
Go to page 69 in text book and look
