Question
Mon April 13, 2015 By: Priyanshu Jain

Can I get general formulas for solving numericals of this chapter??

Expert Reply
Hanisha Vyas
Mon April 13, 2015
  • One mole is the amount of a substance that contains as many particles or entities as there are atoms in exactly 12 g (or 0.012 kg) of 12C.
  • Following relations given below can be summarized as
    • One mole of atoms = atoms = Gram atomic mass of an element.
    • One mole of molecules = molecules = Gram molecular mass of a substance.
  • The concentration of a solution can be expressed in any of the following ways: Mass per cent, mole fraction, molarity and molality.
  • Molarity is the number of moles of solute in per liter of solution. Unit is moles per liter.

 

  • Molality is the number of moles of solute present in 1 kg of solvent.

 

  • Molecular formula shows the exact number of different types of atoms present in a molecule of a compound.
  • If the mass per cent of various elements present in a compound is known, then its empirical formula can be determined.
  • Where, n is a simple number and may have values 1, 2, 3….
  • Following steps should be followed to determine empirical formula of the compound:
    • Step 1: Conversion of mass per cent of various elements into grams.
    • Step 2: Convert mass obtained in step 1 into number of moles.
    • Step 3: Divide the mole value obtained in step 2 by the smallest mole value (out of the mole value of various elements calculated).
    • Step 4: In case the ratios are not whole numbers, they may be converted into whole numbers by multiplying by a suitable coefficient.
    • Step 5: Write empirical formula by mentioning the numbers after writing the symbols of respective elements.'
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