MCQ practice · SSC Chemistry Board questions · Chapter 6: Concept of Mole and Chemical Counting
How many moles are there in 100 g of potassium dichromate?
Think it through first, then pick an option.
- a 100 M
- b 0.940 M
- c 0.333 M
- d 0.340 M
Answer and explanation
Correct answer: d 0.340 M
M = 294, n = 100/294 = 0.340. (The question prints M where the unit should be mol.)
Why the other options are wrong
- a 100 M: 100 would need M = 1; K₂Cr₂O₇ = 294, so n = 100/294 = 0.340.
- b 0.940 M: 0.94 comes from dividing by 106 (Na₂CO₃); K₂Cr₂O₇ is 294.
- c 0.333 M: 0.333 comes from taking M = 300; the right M = 2 × 39 + 2 × 52 + 7 × 16 = 294.
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