Chemistry - Acids, Bases and Salts

WJEC

What ions do acids produce when they are dissolved in water?

Hydrogen ions (e.g. hydrochloric acid)

What ions do alkali’s produce when they dissolve in water?

Hydroxide ions (e.g. Sodium Hydroxide)

When does a neutralisation reaction happen?

When an acid and an alkali ‘cancel eachother out’.

What does a neutralisation reaction create?

A salt and a water

Acids will react with metals to make a..

salt and hydrogen gas.

What reaction does hydrogen gas cause?

bubbling meaning the reaction is exothermic.

Alkalis are commonly..

metal hydroxides.

Bases are commonly..

metal oxides.

Acids will react with carbonates to make..

a salt, water and carbon dioxide gas.

Strength

How much of the acid ionises in water.

Concentration

How many moles of H+ ions are in a unit of volume.

How do you test for carbon dioxide gas and what is the positive result?

Bubble the gas through the limewater (calcium hydroxide solution) and it will turn milky (cloudy) if carbon dioxide is present.

How do you test for sulphate ions and what is a positive result?

First add dilute hydrochloric acid, followed by barium chloride solution. A white precipitate will form if sulphate ions are in this solution.

What is the first step to making soluble salts (practical)

Heat acid till warm then add metal/base/carbonate and stir thoroughly until it not longer appears.

What is the second step to making soluble salts (practical)

Filter the mixture to remove excess base and transfer the solution to an evaporation basin.

What is the third step to making soluble salts (practical)

Evaporate water from solution using a Bunsen burner till crystals appear.

What is the fourth step to making soluble salts (practical)

Remove evaporating basin from heat and allow filtrate to dry and crystalise.

What are two indicators that show this reaction is taking place (practical)

• bubbling/fizzing/effervescence

• colour change

• temperature increase

What is the calculation for concentration (mol/dm3)

Concentration (mol/dm3) = number of moles volume (dm3