Assume that thermal decomposition of mercuric oxide, HgO, follows first-order ki
ID: 928884 • Letter: A
Question
Assume that thermal decomposition of mercuric oxide, HgO, follows first-order kinetics. It can be followed by the production of oxygen gas as a product:
2HgO(s) 2Hg(l) + O2 (g)
At a particular temperature, k = 6.02 × 104 s 1 . If 1.00 gram of HgO were present initially, how long would it take to produce (a) 1.00 mL of O2 (g) at STP; (b) 10.0 mL of O2 (g) at STP? (STP = standard temperature and pressure for a gas, 273.15 K and 1 bar.)
how do you solve for 0.019375g of HgO, how do I get this number from mL of O2?
Answer: (a) 32.4 s (b) 356 s
Explanation / Answer
2HgO(s) ----> 2Hg(l) + O2 (g)
a) no of mol of O2 = PV/RT*mWT OF O2 = ((1*0.001)/(0.0821*273.15))
= 4.46*10^-5 mol
No of mol of HGO reacted = 4.46*10^-5*2 = 8.92*10^-5 mol
mass of HGo reacted = 216.59*8.92*10^-5 = 0.01932 GRAMS
K = 1/Tln(A/X)
6.02*10^(-4) = (1/T)ln(1/(1-0.01932))
T = 32.4 sec
b)
no of mol of O2 = PV/RT*mWT OF O2 = ((1*0.01)/(0.0821*273.15))
= 4.46*10^-4 mol
No of mol of HGO reacted = 4.46*10^-4*2 = 8.92*10^-4 mol
mass of HGo reacted = 216.59*8.92*10^-4 = 0.1932 GRAMS
K = 1/Tln(A/X)
6.02*10^(-4) = (1/T)ln(1/(1-0.1932))
T = 356.61 sec