Acids, Bases, pH and oxides

Which solid reacts with dilute acid to produce the gas shown in the video?

• carbon

• magnesium

• magnesium oxide

• sodium carbonate

Answer explanation

carbon is a non-metal, Magnesium oxide is a base, magnesium produces hydrogen gas

This colour chart represents that of an universal indicator. If a few drops of universal indicator is added to the potassium hydroxide, what would be the final colour?

​ (a)   ​

• purple
• red
• green
• blue

Given the colour chart of universal indicator and red cabbage indicator, which pH range do they show the same colour?

• 2-3

• 3-5

• 6-7

• 8-9

• 10

These stains on taps and sinks are due to calcium carbonate. Suggest a way to remove this stains.

Answer explanation

Acid can be added to remove these stains such as vinegar, lemon juice

Which of the follow is able to react with both hydrochloric acid and sodium hydroxide?

• Zn

• CO₂

• MgO

• ZnO

Answer explanation

amphoteric oxides

Baking powder is dissolved in water.

Universal Indicator is added and the colour of the solution is compared to a pH colour chart. The solution has a pH of 9. Hence baking soda is a ________.

• strong acid.

• strong alkali.

• weak acid.

• weak alkali.

Flowers of a hydrangea bush are shown in the picture. Which of the following can be concluded from the picture?

• Flowers of a hydrangea bush are pink when grown in acidic soil

• citric acid can be added to acidic soils to get pink flowers of hydrangea

• Flowers of a hydrangea bush are blue when grown in acidic soil

• calcium hydroxide can be added to acidic soils to get pink flowers of hydrangea

What type of reaction happens between hydrochloric acid and sodium hydroxide?

The gas produced indicates a reaction between

• sodium hydroxide and sulfuric acid

• sodium and sulfuric acid

• sodium hydroxide and ammonium chloride

• sodium oxide and water

Which ionic equation represents the neutralisation of aqueous sodium hydroxide with dilute nitric acid?

• H⁺ + OH^- → H₂O

• Na⁺ + NO₃^- → NaNO₃

• Na⁺ + HNO₃ → NaNO₃ + H⁺

• NaOH + H⁺ → Na⁺ + H₂O