Chemistry - Acids, bases and salts Flashcards
What are indicators?
Indicators are substances that change colour when they are added to acids and alkalis.
What do acids produce when dissolved in water?
Acids produce hydrogen ions, H+, when they dissolve in water
What do alkalis produce when dissolved in water?
Alkalis produce hydroxide ions, OH–, when they dissolve in water
What is a neutralisation reaction?
A neutralisation reaction happens when an acid and an alkali ‘cancel each other out’. The reaction always produces a salt and water.
The H+ ions from the acid react with the OH– ions from the alkali to form water.
The name of the salt produced depends upon the acid and alkali that react
What is the difference between strong and weak acids?
- Strong acids fully dissociate (ionise) in water whereas weak acids only partially dissociate.
- Strong acids have high numbers of H+ ions in their solutions, so low pH values.
- Strong acids react more quickly than weak acids.
- The temperature rise during the reaction between magnesium and a strong acid is higher than that with a weak acid.
What is the difference between acid strength and concentration?
-The strength of an acid is a measure of the degree of its dissociation.
-The concentration of an acid is a measure of the number of moles of acid in 1 dm3 of solution
What are the reactions of acids?
-Acids react with metals, bases and carbonates to form salts.
-The name of a salt formed has two parts. The first part comes from the metal, base or carbonate. The second part comes from the acid.
What is the reaction between metals and acids?
-Acids will react with metals to make a salt and hydrogen gas.
-The hydrogen causes bubbling during the reaction. The reaction is exothermic.
-The more reactive the metal, the faster the reaction is, resulting in more bubbling and a bigger temperature rise.
What is the reaction between acids and carbonates?
-Acids will react with carbonates to make a salt, water and carbon dioxide gas.
-The carbon dioxide causes bubbling during the reaction. The reaction is exothermic.
What is a base?
A base is chemically opposite to an acid. Some bases dissolve in water and are called alkalis. Other bases, including many metal oxides, do not dissolve in water.
How do you detect hydrogen when reacting with an acid?
The hydrogen causes bubbling during the reaction, and can be detected using a burning splint which produces a squeaky pop sound.
How do you detect carbon dioxide in a liquid?
The carbon dioxide causes bubbling during the reaction, which is observed as fizzing. It can be detected by passing the gas through limewater, which will go cloudy.
Where can you use an acid and carbonate reaction?
-can be used to test unknown solutions to see if they are acidic. Simply add a solution of sodium carbonate to the solution and if carbon dioxide gas is given off, the solution is acidic.
-can also be used to test unknown solutions for the presence of carbonate (CO3–) ions. Simply add an acid to the solution and if bubbles of carbon dioxide are given off, the solution contains carbonate ions.
How do you obtain pure salt form a reaction?
evaporation
- A solution is placed in an evaporating basin and heated with a Bunsen burner
- The amount of the solution has reduced through evaporation
- The solution has evaporated, leaving a crystallised solute
How do you create an insoluble salt?
To make an insoluble salt, two soluble salts need to react together in a precipitation reaction. A reaction in which an insoluble solid is formed when certain solutions are mixed.
