chemistry

The equation shows the reaction of sodium with water.
2Na(s) + 2H20() -
→ 2NaOH(aq) + H2(g)
A sample of sodium of mass 0.138 g reacts with excess water.
Calculate the volume of hydrogen, in cm', produced at room temperature and pressure (rtp).
The volume of one mole of a gas at rtp is 24 000 cm']

Reply 1

eriksks

0.138/23 (Mr Na = 23) = 0.006
0.006/2 (because 2 mol Na) = 0.003
0.003 x 24000 = 72cm³

Reply 2

Nitrotoluene

Hello mariam abdel!

You first determine the number of moles of sodium that reacted with two moles of water to produce one mole of hydrogen . The molar mass of sodium is 22.98 g/mol and the reaction is 2Na(s) + 2H2O() = 2NaOH(aq) + H2(g).

Since the reaction is 2Na(s) + 2H2O() = 2NaOH(aq) + H2(g), one mole of sodium reacts with two moles of water to produce one mole of sodium hydroxide (NaOH) and one mole of hydrogen gas (H2). The reaction produces one mole of hydrogen for every two moles of sodium reacted.

The ideal gas equation can be used to find the volume of hydrogen gas produced at room temperature and pressure. Choose the gas constant "R" carefully, paying attention to the units of measurement involved.

The volume is then calculated by rearranging the equation and dividing by the number of moles.

The volume is then converted from litres to cubic centimeters (cm^3).

EDIT: You can also follow eriksks' quick solution.
Kind regards,
Sandro

(edited 1 month ago)

Reply 3

TypicalNerd

Whilst Sandro's method would be valid, I would strongly suggest you instead follow the solution given by eriksks - the ideal gas equation is not taught at GCSE and even if it was, there is not enough data given to use it. Furthermore, use the relative atomic mass of sodium as given by the periodic table supplied in your exams (this should be exactly 23 - more precise values may result in your answer being "off" the expected answer, thus losing you marks).