Question

According to STP, 1 volume of water is equal to how much volume of steam??

Answer 1

In general 1 volume of water is equal to 22.4 liter for calculationmolar volume, the volume occupied by a mole of a substance at STP. According to Avogadro's law, at a given temperature and pressure a given volume of any gas contains the same number of molecules. At STP 1 mole of gas occupies 22.414 liters. This volume is what is usually meant by the molar volume, although one can also speak of molar volumes of substances that are not gaseous at STP. Since at STP water occupies very nearly 1 cc per gram, and since 1 mole of water molecules weighs very nearly 18 grams, the molar volume of water is about 18 cc. The molar volume of osmium, one of the densest metals, is only about 8.4 cc; that of beryllium is only about 4.86 cc.STP means  standard temperature and pressure..
     Temperature is  25 deg. C  or  298 deg Kelvin..
     Pressure is 1 atmosphere.. 1.013 * 10^5  Pascal or N/m²  or  1 bar
 take 1 litre of water   1 kg .  
One litre of water contains  1000 gms/ 18 gms = 500/9 moles of water.
 At STP one mole of an ideal gas occupies  22.4 litres.  So 500/9 moles occupy  500 * 22.4/9 
 one volume of water is equal to  1244.44  volumes of steam.
 .  One mole of steam will occupy  22, 400 cc of volume of ideal gas.
  So  18 cc  water    22, 400 cc of steam
   1 volume of water    22, 400 / 18  volumes of  steam.

Answer 2

STP means  standard temperature and pressure..
     Temperature is  25 deg. C  or  298 deg Kelvin..
     Pressure is 1 atmosphere.. 1.013 * 10^5  Pascal or N/m²  or  1 bar

Suppose we take 1 litre of water which is nearly  1 kg of water. 

One litre of water contains  1000 gms/ 18 gms = 500/9 moles of water.

Let us treat (dry) steam as an ideal gas.  At STP one mole of an ideal gas occupies  22.4 litres.  So 500/9 moles occupy  500 * 22.4/9  litres.

Thus one volume of water will be equal to  1244.44  volumes of steam.

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alternately, 

   you take  18cc or ml  of water.  this is equal to one mole of water.  One mole of water becomes one mole of steam.  One mole of steam will occupy  22, 400 cc of volume at STP, assuming (dry) steam to be an ideal gas.

  So  18 cc  water  =>  22, 400 cc of steam
   1 volume of water  ==>  22, 400 / 18  volumes of  steam.