ACIDs and BASEs
A substance that donates protons or produces H⁺ ions in water.
What is an acid?
Changes colour to show whether a substance is acidic, basic or neutral.
An indicator
What pH is neutral?
pH 7
What are the two main products of neutralisation?
Salt and water
What gas is produced when an acid reacts with a metal?
Hydrogen gas
Usually taste bitter, feel slippery, may be corrosive, and are often insoluble in water.
Properties of bases
What colour does blue litmus turn in an acidic solution?
Blue litmus turns red in an acidic solution.
Is a substance with pH 3 acidic, neutral or basic?
Acid
What is the general word equation for neutralisation?
Acid + base → salt + water.
What two visible changes might occur when magnesium reacts with acid?
Bubbles or fizzing as gas is released, and the magnesium gradually dissolves.
Bases that dissolves in water
Alkali
What does universal indicator tell you that litmus paper cannot?
Universal indicator provides an approximate pH and indicates how acidic or basic a solution is. Litmus mainly identifies whether a substance is acidic or basic.
Which is more acidic: pH 2 or pH 5?
pH 2
Which two ions combine to form water during neutralisation?
Hydrogen ions (H⁺) and hydroxide ions (OH⁻). They combine to form water: H⁺ + OH⁻ → H₂O.
What salt forms when magnesium reacts with hydrochloric acid?
Magnesium chloride
How many times greater is the hydrogen ion concentration at pH 2 than at pH 4?
100 times greater. Each pH unit represents a tenfold difference, and two units represent 10 × 10 = 100.
Hydrochloric acid reacts with sodium hydroxide. Name the salt formed and write the complete word equation.
Sodium chloride.
Hydrochloric acid + sodium hydroxide → sodium chloride + water.
Write the word equation for zinc reacting with sulphuric acid.
Zinc + sulphuric acid → zinc sulphate + hydrogen gas.
Solution A has pH 3 and Solution B has pH 6. How many times greater is the hydrogen ion concentration in Solution A?
1,000 times greater. The difference is three pH units: 10 × 10 × 10 = 1,000.
Magnesium reacts with hydrochloric acid. Identify the products.
Magnesium chloride and hydrogen gas.