Molar mass
Molar mass is a Science & Technology concept from the MPSC syllabus, tested in 5 past MPSC questions (2019, 2021, 2023). Below are those real questions with their correct answers and explanations, plus the concepts worth being comfortable with first.
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180 ग्रॅम अॅसेटिक आम्ल (CH3COOH) आणि 180 ग्रॅम पाणी (H2O) एकमेकांत मिसळले. तयार झालेल्या द्रावणात अॅसेटिक आम्लाचा मोल फॅक्शन ______ इतका असेल. [H = 1, C = 12, O = 16] 180 g of acetic acid (CH3COOH) is mixed with 180 g of water (H2O). The mole fraction of acetic acid in the resultant solution is [H = 1, C = 12, O = 16]
Molar mass of CH3COOH = 12+3+12+16+16+1 = 60 g/mol. Moles of CH3COOH = 180 / 60 = 3. Molar mass of H2O = 18 g/mol. Moles of H2O = 180 / 18 = 10. Mole fraction of acetic acid = Moles of acid / Total moles = 3 / (3 + 10) = 3 / 13 = 0.23.
'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).
10 ग्रॅम वायुरूप हायड्रोजनमध्ये H₂, मानक दाब आणि तापमानात हायड्रोजनचे _________ मोल असतात. 10 g of gaseous hydrogen H₂, at NTP/STP contain _________ mol of hydrogen.
Number of moles is calculated as given mass divided by molar mass. Molar mass of H2 is 2 g/mol. So, 10 g / 2 g/mol = 5 moles.
32 ग्रॅम मिथेन (रेणु वस्तुमान 16 g/mol) आणि 192 ग्रॅम ऑक्सिजन (रेणु वस्तुमान 32 g/mol) एकत्र मिसळले. हे दोन वायू जर एकमेकांशी रासायनिक प्रक्रिया करत नसतील तर मिथेन वायूचे मोल फ्रॅक्शन किती ? / 32 g of methane (molar mass 16 g/mol) is mixed with 192 g of oxygen (molar mass 32 g/mol). Presuming that these gases donot react with each other, what is the mole fraction of methane ?
Moles of methane = 32/16 = 2 moles. Moles of oxygen = 192/32 = 6 moles. Total moles = 2 + 6 = 8 moles. Mole fraction of methane = Moles of methane / Total moles = 2/8 = 0.25 (or 1/4).