2Na + 2H2O ----> H2 + 2Na(OH)
48.7/23 = 2.12 moles sodium
2.12/2 x 24 = 25.44dm^3 hydrogen = 1.06 moles
1.06 X 6.02x10^23 = 1.204x10^24 molecules of hydrogen
With the palm of your hand, push the lid down, as you apply this pressure on the lid twist slightly. Once you are able to get movement, use your fingers to keep twisting until the lid is completely off. :)
You should probably ask your teacher the next day, there may be a mistake.