10th std science and technology practical note book answers
Answers
1. The two colours seen at the extreme ends of the pH chart are
(a) red and blue.
(b) red and green.
(c) green and blue.
(d) orange and green.
ANSWER - (a) red and blue.
REASON - Red colour is at the top and blue colour is at the bottom.
2. A student observed that the colour of pH paper changes to green when she dipped it in water. She added a few drops of concentrated hydrochloric acid to the water. The colour of pH paper would turn to
(a) light red.
(b) apple green.
(c) dark blue.
(d) lemon yellow.
ANSWER - (a) light red.
REASON - The colour of pH paper is green in neutral medium, whereas it is red in acidic medium.
3. When zinc reacts with dilute hydrochloric acid
(a) the surface of zinc becomes brighter.
(b) the surface of zinc becomes black and dull.
(c) the metal turns into powder.
(d) the reaction mixture turns green.
ANSWER - (b) the surface of zinc becomes black and dull.
REASON - The surface becomes black and dull as the reaction proceeds.
Disclaimer - Kindly provide exact Question.
Explanation:
what is indicated by time temperature graph in above activity