Question

Sometimes in lab we collect the gas formed by a chemical reaction over water (see sketch at right). This makes it easy to isolate and measure the amount of gas produced. Wala Suppose the H, gas evolved by a certain chemical reaction taking place at 40.0 °C is collected over water, using an apparatus something like that in the sketch, and the final volume of gas in the collection tube is measured to be 80.0 mL. Sketch of a gas-collection apparatus Calculate the mass of H, that is in the collection tube. Round your answer to 2 significant digits. You can make any normal and reasonable assumption about the reaction conditions and the nature of the gases. XS ?

Answer 1

I suppose H₂ as an ideal gas and the initial volume is 0 according to the initial conditions of this exercise. I suppose the pressure is 1.0 atm

The temperature in Kelvin degrees is 303K (40^oC=303K) adding 273 to Celsius degrees temperature.

Final volume is 80.0ml.

Let`s start to use the ideal gas equation:

P*V=nh, *R*T

P=1.0atm

V=80.0ml

T=303K

The number of moles of hydrogen is calculated by this equation:   

m2 nH2 FW:

FW H₂=2.0g/mol

I must replace last equation into the ideal gasses equation:

mh, *R*T P*V = FWH

P*V* FWH R*T

0.08L *2.mol = MHz 1.0atm * 0.08L * 2.0-9 0.082 atm. * * 303K

тн, = 0.00648