Acids, alkalis and indicatorsIB MYP Chemistry: Mind map

Exam questions on Acids, alkalis and indicators

1. Students at a school in Singapore test four household liquids with litmus paper: lemon juice, vinegar, soapy water and oven cleaner.
   Soapy water is an alkali. State what happens to red litmus paper in soapy water and name the ion that makes the solution alkaline.2 marks
2. A student compares two acids of the same concentration. Hydrochloric acid turns universal indicator red, but ethanoic acid turns it orange-yellow. When identical strips of magnesium ribbon are added, bubbles of gas appear much faster in the hydrochloric acid than in the ethanoic acid.
   Identify two control variables that the student must keep the same for a fair comparison of the two acids.2 marks
3. A science teacher in Nairobi makes an indicator by boiling red cabbage leaves in water. She adds a few drops to three colourless liquids: lemon juice turns it pink, distilled water leaves it purple, and a solution of washing soda turns it green. Later, the class compares the cabbage indicator with litmus paper and universal indicator.
   State what the results show about each of the three liquids.3 marks