Molar mass

Tested in 5 real MPSC questions across 2 years (2021–2023). See it in context on the interactive Concept Graph →

Years it was asked

2023 2021

What you need to know first

Concept of moleSolution concentration unitsAtomic weightsBasic chemistry formulasBasic Division

Real questions that test this

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]

a)0.23&check; Correct

b)1.0

c)0.5

d)वरीलपैकी कोणताही नाही / None of the above

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.

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.

1)10

2)5&check; Correct

3)1

4)0.1

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.

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