Back in the air – part I

In follow up on our latest adventure in Envelope from Windreiter we’ve ended up some amazing progress this weekend. Our plan was to get heaps of it from Aluminium and Sodium Hydroxide Reaction | Al + NaOH.

Christopher dug out for us how it should work – one sodium atom, one oxygen atom, and one hydrogen atom make up this compound. When all of the molar masses of the constituents of sodium hydroxide are added together, the result is sodium hydroxide’s (NaOH) molar mass. Thus, 22.989g/mol+15.999g/mol+1.008g/mol=39.996g/mol.

So approx 40g of caustic soda = 1g hydrogen.

Molar volume, or volume of one mole of gas , depends on pressure and temperature, and is 22.4 litres – at 0 °C (273.15 K) and 1 atm (101325 Pa), or STP (Standard Temperature and Pressure), for every gas which behaves similarly to an ideal gas. The ideal gas molar volume increases to 24.0 litres as the temperature increases to 20 °C (at 1 atm).

For an ideal gas, the attractive or repulsive interactions between the molecules of gas can be neglected, therefore we can treat this gas as “ideal”. (Side Note: interaction forces between specific gases create conditions for non-ideal gas situations)

The actual molar volume of hydrogen can be exactly calculated from the experimental density of that gas, that is 0,0899 g/L at 0 °C (1 atm ) and 0.0837 g/L at 20 °C (1 atm), knowing that one mole of dihydrogen (H2) amounts to 2,0159 g/mol. Thus, if 0,08988 grams amount to 1 litre, a mole will be as big as 2,0159/0,0899 = 22,42 litres at STP (0 °C – 1 atm) and 2,0159/0,0837 = 24,1 litres.

These values of true molar volume of hydrogen are very close to the ideal gas values of 22,41 L/mol and 24,0 L/mol at 0 °C and 20 °C, respectively, thus confirming that hydrogen gas behaves almost ideally.

As always it needed some shopping to be done first to get our Hydrogen production back on rails. We started with getting 0.5 kg of Aluminium powder from Barnes.

It looks so tiny when having it in hand.

Getting Caustic Soda from Santo was much more entertaining as they keep selling it in 25kg bags only.

Of course, handling such material might be mildly problematic, we’ve got proper protection ready.

Next phase started by putting together the “reaction chamber” by scavenging on our previous hydrogen generator. Mainly our original investment into the Teflon coating paid off thousand times as the main basin needed to be corrosion resistant to withstand that caustic soda solution, while also having high thermal conductivity to disperse heat from planned (exothermic) reaction.

As a lid we’ve used an old perspex sheet and drilled couple holes to get solution feed in and hydrogen outlet. Whole contraption got placed in an esky filled with water to cool things down and also to capture any potential leaks.

Moments later we’ve started generating our first Hydrogen!

And few moments later, with assistance from Ondra, we had our blimpy back again.

At that stage we had to stop our test as it was getting late and we had some other activities.

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