Question

Choose the correct answer.
1. Lemon juice contains _________acid.
a) Acetic b) Lactic c) Citric d) Tartaric
2. Curd contains _______acid.
a) Acetic b) Lactic c) Citric d) Tartaric
3. The colour of litmus is _______ in distilled water
a) Purple b) Blue c) Red d) Yellow
4. Which of the following substances present in turmeric changes its colour on reacting with base?
a) Lichen b) Curcumin c) Magnesia d) None of these
5. Sodium bicarbonate is commonly known as
a) Lime water b) Washing soda c) Slaked lime d) Baking soda.
6. The colour of phenolphthalein is ________ in basic solution.
a) Purple b) Blue c) Red d) Pink

Answer 1

The answer to these questions is based on some general topics of chemistry and also some are on the laboratory experiment where phenolphthalein is used as redox indicator and the litmus paper used for the determination of acidity and basicity of the solution.

Complete step by step answer:
In the lower classes, we have come across some of the basic concepts of chemistry which is used in the day to day life and also many experiments we carry out in the laboratories.
Let us now see in detail about each of the sub questions given and find the required answers.
In the first question that is,
1. The lemon juice is common and naturally available by the plants and is used for the sour taste to be given for food.
Usually, the sour taste of this lemon juice is mainly because of the chemical called the citric acid and other options given where lactic acid doesn’t have much taste , tartaric acid tastes like tart that is salty and acetic acid has distinctive sour taste but with a pungent smell.
Thus the correct answer for this sub question will be option c)

2. In this question, the most common product obtained from cow milk is the curd used as the main source of food. The acid which is present in this is the lactic acid where this is responsible for making curd.
Thus, the correct answer is option b)

3. From the laboratory experiments, we know the use of litmus paper for determination of whether the solution is acidic or basic.
Now, the red litmus paper turns blue which indicates that the solution is basic and the blue litmus paper turns red which indicates the presence of acid.
Since the distilled water is a neutral solution and the litmus is extracted naturally from lichens which is purple in colour, the colour remains the same.
Thus correct answer is option a)

4. Turmeric is yellow in colour and when this reacts with base it turns to be pink in colour which is because of the main active ingredient curcumin present in it but the colour remains same with acid and neutral solution.
Thus, correct answer is option b)

5. Sodium bicarbonate is the chemical used for the baking of the food products and thus the common name given is baking soda.
Therefore, the correct answer is option d)

6. Phenolphthalein is the basic redox indicator used in the laboratories as an indicator for the acid – base titrations.
When there is a basic solution, the colour phenolphthalein is pink and in acidic solution it is colourless.
Thus, correct answer is option d)

Note: Note that the baking soda is a common name given for the chemical sodium bicarbonate and washing soda is the common name given for the chemical sodium carbonate and do not confuse these two terms.