CBSE Class 10 Science 2019 · Paper 31/1/1/C · Question 22(a)
On adding a few drops of universal indicator in three colourless solutions X, Y and Z taken separately in three test tubes, a student observed the changes in colour as green in X, red in Y and blue in Z.
- (a)Arrange X, Y and Z in increasing order of their pH values.
- (b)Which one of the three, X, Y and Z, will change the colour of phenolphthalein ? Why ?
Answer
Increasing pH order is Y, X, Z; Z changes phenolphthalein because it is basic.
(a) Y (red: strongly acidic, pH about to ) < X (green: neutral, pH ) < Z (blue: basic, pH about to ). The increasing order of pH is Y, X, Z.
(b) Z. Phenolphthalein is colourless in acidic and neutral solutions and turns pink only in a basic solution. Z is basic (pH more than ), so it turns phenolphthalein pink, while X and Y leave it colourless.
🔒 Step-by-step solution
Sign up free to see every step of how it is worked out.
From the board papers
More questions from Acids, Bases and Salts
Class 10 Science — every question with an expert-verified, step-by-step solution.
- Q1 A solution turns red litmus blue, its pH is likely to be
- Q1 You have been provided with three test tubes. One of them contains…
- Q2 A solution reacts with crushed egg-shells to give a gas that tu…
- Q3 10 mL of a solution of NaOH is found to be completely neutralised b…
- Q4 Which one of the following types of medicines is used for trea…
- Q5 Write word equations and then balanced equations for the reaction t…
- Q6 Compounds such as alcohols and glucose also contain hydrogen bu…
- Q7 Why does distilled water not conduct electricity, whereas rain wat…
- Q8 Why does dry HCL gas not show acidic behaviour in the absence of…
- Q9 Five solutions A, B, C, D and E when tested with universal indicato…
- Q10 Equal lengths of magnesium ribbons are taken in test tubes A and B.…
- Q11 Fresh milk has a pH of 6. How do you think the pH will change as i…
All 352 questions on Acids, Bases and Salts → Browse all Science chapters →