Question

Need help filling in my data sheet from a lab. My professor said the pressure was 24.6 inches of Hg and that we needed to convert that to moles. Im not sure i put that in the correct spot. I included the lab protocol. Plz plz plz help me fill in the blanks and let me know if i did something wrong Im very confused haha. THANKS!!

Equivalent Mass by Electrolysis If the two terminals on any source of DC voltage are connected through metal electrodes to a conducting liquid an electric current will pass through the liquid and chemical reactions will occur at the two metal electrodes. At the electrode connected to the negative pole of the battery a reduction reaction will invariably be observed. In this reaction electrons will usually be accepted by one of the species present in the aqueous solution. The species reduced will ordinarily be a metallic cation or the H occurs with the least expenditure of electrical energy and will depend on the composition of the solution. In the electrolysis cell that we shall study the reduction reaction of interest will occur in an acidic medium where hydrogen gas will be produced by the reduction of hydrogen ions ion or possibly water tself. The reaction observed will be the one that (1) 2H(a) +2e1 H2(g) In terms of moles we can say that the production of one mole of H2(g) requires two moles of electrons. A mole of electrons is called a faraday, after Michael Faraday who discovered the basic laws of electrolysis. The amount of a species which will react with a mole of electrons is equal to the equivalent mass of that species. Since one faraday will reduce one mole of H ion we say that the equivalent mass of hydrogen is 1.008 grams, which is equal to the mass of one mole of H ion (or 1/2 mole of H(g)). To form one mole of H:(g) one would have to pass two faradays through the electrolysis cell. In the electrolysis experiment we will perform we will measure the volume of hydrogen gas produced under know Law we will be able to calculate how many moles of H: were formed and hence how many faradays of electricity passed through the cell (2 mol e per mol of Hz(g)). In the oxidation halfreaction of an electrolysis cell an oxidation reaction will occur in which some species will give up electrons. This reaction, which takes place at the anode in the cell, may involve an ionic or neutral species in the solution or the metallic electrode itself. In the cell that you will be studying the pertinent oxidation reaction will be that in whicha metal under study will participate n conditions of temperature and pressure . By using the Ideal Gas (2) M(s)M(aq)+ ne During the course of the electrolysis the atoms in the metal will be converted to metallic cations and will go into the solution. To oxidize one mole of the metal it would take n faradays where n is the charge on the cation that is formed. By definition one faraday of electricity would cause one equivalent mass, EM, of metal to go into solution. The molar mass, MM, and the equivalent mass of the metal are related by the equation:

Answer 1

Pressure exerted by dry hydrogen : 1 inches of Hg = 0.0334 atm

24.6 inches of pressure ==> ? = 0.8222 atm

Temperature , T = 294.55 K

Volume of hydrogen for trial 1 : 36.8 ml = 0.0368 l

Volume of hydrogen for trial 2 : 33.4 ml = 0.0334 l

According to ideal gas equation :

PV = nRT

R = Ideal gas constant = 0.08206 lt atm/mol K

Trial 1:

0.8222 atm x 0.0368 = n x 0.08206 lt atm/mol K x 294.55 K

0.03026 mol /24.17 = n

No. of moles of hydrogen produced for trial 1 : 0.00125 moles

Trial 1:

0.8222 atm x 0.0334 = n x 0.08206 lt atm/mol K x 294.55 K

0.02746 mol /24.17 = n

No. of moles of hydrogen produced for trial 2 : 0.00114 moles

On average No. of moles of hydrogen produced = 0.00125 moles+0.00114 moles)/2 = 0.001195 moles

For each mole of hydrogen the number of faradays of electrons passed are 2 electrons

so 0.001195 moles of hydrogen = 0.00239 faradays are produced

Based on the mass of metal electrode loss (i.e mass of metal electrode before and after electrolysis) the equivalent mass of metal can be calculated

Equivalent mass of metal = loss of mass of metal / no. of faradays passed