Acids, Bases And Salts Flashcards
If red litmus is placed in an alkaline solution it will turn?
Blue
If blue litmus is placed in an acidic solution it will turn?
red
Both papers will turn______in a neutral solution
They will not change
Can litmus paper determine the pH of a solution?
Litmus cannot be used to determine the strength of a solution and therefore cannot be used to determine the pH
What is the pH scale?
The pH scale is a scale used to measure how acidic or how alkaline a solution is. The pH scale runs from 0 to 14. A pH value of 7 is neutral. A pH value less than 7 is acidic and a pH value more than 7 is alkaline.
What is the pH of a strong acid
pH 0–2 strong acid
What is the pH of a weak acid
pH 3–6 weak acid
What is the pH of a neutral solution
pH 7 neutral
What is the pH of a weak alkali
pH 8–11 weak alkali
What is the pH of a strong alkali
pH 12–14 strong alkali
What could you use to find the pH of a solution to one decimal place?
A pH metre
What do acids produce when they dissolve in water?
hydrogen ions
what do alkalis produce when they dissolve in water?
hydroxide ions
How do strong acids and alkalis ionise in water?
Strong acids and alkalis are completely ionised in water.
How do weak acids and alkalis ionise in water?
Weak acids and alkalis are only partially ionised in water.
What is a concentrated solution?
Contains a large amount of acid particles dissolved per unit volume
What is a dilute solution?
Contains a small amount of acid particles dissolved per unit volume
Formula of Hydrochloric acid
HCl
Formula of sulfuric acid
H2SO4
Formula of nitric acid
HNO3
Formula of ethanoic acid
CH3COOH
Formula of sodium hydroxide
NAOH
Formula of potassium hydroxide
KOH
Formula of Ammonia
NH3
What is a base
A base is
* any metal oxide e.g. calcium oxide
* any metal hydroxide e.g. calcium hydroxide
* any metal carbonate e.g. calcium carbonate
* any metal hydrogen carbonate e.g. calcium hydrogen carbonate
What is an alkali
An alkali is a base that is soluble in water.
Reaction for Metal Carbonate + Acid and Metal Hydrogen Carbonate + Acid
ACID + METAL = METAL SALT + WATER + CARBON
CARBONATE DIOXIDE
ACID + METAL = METAL SALT + WATER + CARBON
HYDROGEN CARBONATE DIOXIDE
Reaction for Metal + Acid
METAL + ACID = METAL SALT + HYDROGEN
Reaction for Ammonia + Acid
AMMONIA + ACID = AMMONIUM SALT
Reaction for Acid + Metal Oxide and Acid + Metal Hydroxide
ACID + METAL OXIDE METAL SALT + WATER
ACID + METAL HYDROXIDE METAL SALT + WATER
What is the chemical test for Hydrogen?
When a lighted splint is placed in a test tube of hydrogen gas there is a squeaky pop. This is a mini-explosion because the hydrogen burns very quickly forming water.
2H₂ + O₂ 2H₂O
What is the chemical test for Oxygen?
When a glowing splint is placed in a test tube of oxygen it will relight.
What is the chemical test for Carbon Dioxide?
When carbon dioxide is bubbled through limewater the limewater changes from a colourless clear solution to a cloudy or milky suspension.
Ca(OH)₂ (aq) + CO₂(g) CaCO₃ (s) + H₂O (l)
(limewater solution)
What is a salt?
A salt is a compound that is formed when some or all of the hydrogen ions present in an acid are replaced by metal ions or ammonium ions.
Describe method one of Preparing salts
The insoluble solid (metal, metal oxide or metal carbonate) is added to the acid until there is excess. The solid is added in excess to ensure all the acid has reacted.
The excess solid is then removed by filtration and the filtrate heated to half the volume and then left to cool and crystallise.
In order to obtain a pure dry sample the crystals are dried between sheets of filter paper or in a dessicator.
Describe method two of Preparing salts
Adding an acid to an alkali,
This method is known as titration and an indicator is used to determine when the acid and alkali have become neutral and the salt has formed.
The indicator can be removed by heating the solution with charcoal.
What colour are most of group l, Group ll, aluminium and zinc compounds and when dissolved in water.
Most Group I, Group II, aluminium and zinc compounds are white in colour and when dissolved in water form colourless solutions.
Why Hazard symbols are used instead of words
- are eye catching
- can be understood by those who cannot read
- are internationally recognised symbols
- are easily recognised symbols indicating a warning
Meaning of Hazard sign Explosive
May explode when heated, exposed to a flame or knocked
Meaning of Hazard sign Toxic
Serious risk of causing death by poisoning when swallowed or breathed -Look in book for symbol
Meaning of Hazard sign Caution
Less poisonous than toxic substances, but must be handled with care. May irritate the skin or eyes -Look in book for symbol
Meaning of Hazard sign Corrosive
Destroy (‘eat away’) flesh and other materials -Look in book for symbol
Meaning of Hazard sign Highly Flammable
Easily catches fire -Look in book for symbol
