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Example 8. Calculate the mass of (i) 0.1 moleof KNO, (ii) 1 X 1023 molecules of methane and(iii) 112 cm of hydrogen at STP. |
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Answer» Answer: Here's yours answer (a) The molar mass of KNO3 is 101 g/mol. Thus 1 mole of KNO3 = 101 g Therefore 0.1 mole of KNO3 = 0.1×101 g = 10.1 g (b) The molar mass of methane (CH4) is 16 g. As there are 6.022×1023 MOLECULES in 1 mole of methane, therefore 6.023×1023 molecules of methane = 16 g of methane 1 molecule of methane = (16 / 6.022 × 1023 ) g of methane 1023 molecules of methane = (16×1023 ) / 6.022×1023 g of methane = 2.657 g (c) 112 cm3 of hydrogen, H2 at STP. 1 mole of hydrogen at STP OCCUPY 22.4 L or 22400 cm3 VOLUME and mass 2 g. Mass of 22400 cm3 of hydrogen = 2 g Mass of 112 cm3 of hydrogen = (2/22400) × 112 = 0.01008 |
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