Question

2Na + 2H2O---> 2NaOH + H2

Need to find the molecules of H2

Atomic wt o Na = 23
48.7 g of Na
48.71/23 = 2.12 mols Na
2.12/2 × 24. (WHERE DOES THE 24 COME FROM) = 25.44 dm^3 H. (PLEASE EXPLAIN THIS PART) = 1.06moles
1.06mols× 6.02×10^23 avagados number=
1.204 × 10^24 molecules

I understand this except where the 24 comes from and the dm^3 parts----please explain

Thank you.

Answer 1

the 24 is a sloppy way of doing unit conversion problems. Let me show you.

Volume of H2=molesH2*volumeH2/mole
=2.12molesNa*1moleH2/2molesNa*22.4dm^3/moleH2=1.06*22.4 dm^2 AT STP.
now, if you are not doing stp conditions, but rather using RTP, At RTP (room temperature and pressure), this volume is 24 dm3 (liters)

See why I called your calculations sloppy? without units, and conditions, it makes no sense.