Question

(A) Give reason: Plastic of Paris should be stared in a moisture proof container
(B) Explain the formation of scum when hard water is treated with soap. ​

Answer 1

Explanation:

the second Q: When a soap is used in hard water, a solid substance we call scum forms. This is because charged calcium and magnesium particles (called ions ) present in the water react with soap to form an insoluble substance. ... The new substance, scum, does not dissolve in water

Answer 2

$Perimeter \: of \: trapezium \: = \: 104 m \\ </p><p></p><p>Length \: of \: Non-parallel \: sides = \: 18 m \: and \: 22 m \\ \\ </p><p></p><p>Altitude = 16m \\ \\ </p><p></p><p>Area \: of \: Trapezium \: = 0.5 * (sum \: of \: parallel \: sides)*altitude ------ (1) \\ \\ </p><p></p><p>Sum \: of \: parallel \: sides = Perimeter - (sum \: of \: non-parallel \: sides) = 104 m - (18+22)m = 104-40 m = 64 m \\ \\ \\ </p><p></p><p>From \: (1), \: Area \: of \: Trapezium = \: 0.5*64*16 \\ \\ \\ = 512 m^2</p><p></p><p>Ans: \: \: Area \: of \: trapezium = 512 m^2$

Ans: Area of trapezium = 512 m^2