SolveItClass 9 · NCERT

NCERT Solutions · Class 9 Science Atomic Foundations of Matter

39 questions · 21 still being checked

Pause and Ponder 9.3 (part 4 of 22)

  1. Exercise 9.3

    A compound consists of 40\displaystyle 40% sulfur and 60\displaystyle 60% oxygen by mass. In a sample of the same compound containing 20\displaystyle 20 g of sulfur, what mass of oxygen must be present to satisfy the Law of Constant Proportions?
    NCERT’s answer
    $\displaystyle 30$ g
    Oxygen present = $\displaystyle 30$ g.
    NCERT_Solution_Class9_Science_Ch9_PP_Q9-3
    A compound has a fixed composition, so sulfur : oxygen \(\displaystyle = 40 : 60 = 2 : 3\) by mass in every sample of it.
    Mass of oxygen \(\displaystyle = \dfrac{60}{40} \times 20 = \dfrac{3}{2} \times 20 = 30\) g.
    Check: total sample \(\displaystyle = 20 + 30 = 50\) g, so sulfur is \(\displaystyle \dfrac{20}{50} \times 100 = 40\%\) and oxygen \(\displaystyle \dfrac{30}{50} \times 100 = 60\%\) — as stated.