Stoichiometry
Stoichiometry is a Science & Technology concept from the MPSC syllabus, tested in 2 past MPSC questions (2019, 2023). Below are those real questions with their correct answers and explanations.
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Real questions that test this
खालीलपैकी कोणत्या हायड्रोकार्बनमध्ये 80% कार्बन असतो ? (H = 1, C = 12) Which of the following hydrocarbon has 80% carbon ? (H = 1, C = 12)
Percentage composition by mass = (mass of carbon / molar mass) x 100. Ethane (C2H6): molar mass = 2(12) + 6(1) = 30. %C = 24/30 x 100 = 80%. For comparison: Methane (CH4) is 75% C, Benzene (C6H6) is 92.3% C, Cyclohexane (C6H12) is 85.7% C -- only Ethane matches the given 80%.
'1 मोल' ही किंमत पुढील कोणत्या किमतीशी समप्रमाणात आहे ? / 1 mole is equal to which quantity from the following?
(a)12 ग्रॅम वजनातील C-12 चे अणू / 12 grams of C-12 atoms
(b)6.022137 × 10²³ अणू (कोणत्याही पदार्थाचे) / 6.022137 × 10²³ atoms (of any material)
(c)555.85 ग्रॅम वजनाचे Fe / 555.85 grams of Fe
(d)1 cm³ आकारमानात बसणारे कोणत्याही पदार्थाचे एकूण अणू / atoms of any material in a volume of 1 cm³
One mole of a substance contains Avogadro's number of particles (6.022 × 10²³) and has a mass equal to its atomic/molecular mass in grams (e.g., 12g of C-12).