Question

give the right answer of 5,10,13

Answer 1

13) dry HCl does not change the colour of blue litmus paper red because:  1)It does not contain hydrogen ion

  2)it does not contain water, it not showing acidify in dry medium

10) A concave mirror is used in solar cooker because it converges light rays coming from infinity to a point so that more heat is produced at the point sufficient to cook the food.