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.

Suppose the CO gas evolved by a certain chemical reaction taking place at 55 degree 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 117 ml.

Calculate the mass of CO 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.

The correct answer is 0.12 grams.

Explanation:

The mass of carbon monoxide or CO collected in the tube can be determined by using the ideal gas equation, that is, PV = nRT.

Based on the given question, P or the pressure of the gas is given as 1 atm, volume of the gas collected in the tube is 117 ml or 0.117 L.

The number of moles or n can be determined by using the equation, mass/molar mass.

R is the universal gas constant, whose value is 0.0821 L atmK^-1mol^-1, and temperature is 55 degree C or 328 K (55+273).

On putting the values we get:

n = PV/RT

= (1 atm*0.117 L) / (0.0821 L atmK^-1mol^-1 * 328 K)

= 0.0043447 mol

Therefore, mass of CO will be moles * molar mass of CO

= 0.0043447 mol * 28 g/mol

= 0.12 g