# Chemistry

equilibrium constant for;
so3 <----> so2 + 1/2o2
is found to be 0.471M^1/2 @ 600deg C
after a quantity of sulfur trioxide is allowed to come to equilibrium in a 1L flask @ 600deg C, 0.2 mol oxygen was found to be present. What mass of sulfur trioxide was initially placed in the flask?

answer is 62.3g but i get 20.9g...?

1. 👍 0
2. 👎 0
3. 👁 46
asked by Maya
1. I get 62.38 g SO3 which rounds to 62.4 g.
............SO3 ==> SO2 + 1/2 O2.
initial......x.......0......0
at equil, O2 = 0.2 mol; therefore, SO2 must be 0.4 mol(2*0.2) and SO3 must be x-0.4. Then
Keq = 0.471 = (SO2)(O2)1/2/(SO3)
0.471 = (0.4)(0.2)1/2/(x-0.4)
Solve for x and multiply by 80 to convert to grams.

1. 👍 0
2. 👎 0
2. I thought so2 would be 0.4, I didn't have so3 correct on my ice table.
I get x as 0.485;
0.471(x-0.4)=(0.4)(0.2)^1/2
0.471x-0.1884=0.04
0.471x=0.2284
But x needs to be 1.18 for so3 to be 0.78M(1.18 - 0.4) to multiply with 80, am i missing something?

1. 👍 0
2. 👎 0
posted by Maya
3. Yes, you are missing something. You need work on your algebra.
0.471(x-0.4) = (0.4)(0.2)^1/2 is ok to here. Your error is in the next step. 0.2^1/2 = 0.4472 and that times 0.4 = 0.17889.
0.471x - 0.1884 = 0.17889
0.471x = 0.17889 + 0.1884 = 0.36729
x = 0.36729/0.471 = 0.7798 moles which in 1L makes it 0.7798M. (And I don't agree with 1.18 for SO3 being needed, either).
0.7798 moles x 80g/mol = 62.38 g SO3. Technically, if the problem uses ONLY 0.2 and 0.4 then there is only one significant figure and we would round 62.38g to 6E1 grams.
Your last statement is not correct. You are SOLVING for x, not x-0.4. x is what we started with (which is what the problem asks for) and x-0.4 is what it is at equilibrium. So we start with 0.7798 moles and at equilibrium it is that - 0.4
Check my answer versus Keq.
(0.4)(0.2)^1/2/(0.7798-0.4) = 0.471, right on the money.

1. 👍 0
2. 👎 0
4. :D thankyou very much for explaining it all,
it seems i was treating the 0.2^1/2 as 0.2*0.5 (being half of one...so wrong!).
To get 0.4472 though, 0.2 needs *2.236, it dawned to me as 2.24, bringing so3 to 62.4g after rounding.
I promise to practice my algebra.
I appreciate your brilliance.

1. 👍 0
2. 👎 0
posted by Maya

## Similar Questions

1. ### apchemistry

The numerical value of the concentration equilibrium constant for the gaseous reaction 2 SO2 + O2 *) 2 SO3 is 0.5 at temperature T. When a reactionmix- ture is brought to equilibrium, [O2] is found to be 2.0 M and [SO3] is found

asked by cheri on January 30, 2013
2. ### Chemistry

An equilibrium mixture of SO2, O2, and SO3 at 1000 K contains the gases at the following concentrations: [SO2] = 3.77 10-3 mol/L, [O2] = 4.30 10-3 mol/L, and [SO3] = 4.13 10-3 mol/L. Calculate the equilibrium constant, K, for the

asked by Rachel on April 16, 2011
3. ### chemistry

sulfur trioxide gas dissociates into sulfer dioxide gas and oxygen gas at 1250 degrees C. In an experiment, 3.6 moles of sulfur trioxide were placed into an evacuated 3.0-L flask. THe concentration of sulfur dioxide gas measured

asked by alexa on April 29, 2007
4. ### P. Chemistry

The equilibrium 2 SO2(g) + O2(g) 2 SO3(g) has the value K = 2.5 1010 at 500. K. Find the value of K for each of the following reactions at the same temperature. (a) SO2(g) + 1/2 O2(g) SO3(g) K = (b) SO3(g) SO2(g) + 1/2 O2(g) K =

asked by Tommy on February 15, 2010
5. ### chemistry

An equilibrium mixture of SO2, O2, and SO3 at 1000 K contains the gases at the following concentrations: [SO2] = 3.77 10-3 mol/L, [O2] = 4.30 10-3 mol/L, and [SO3] = 4.13 10-3 mol/L. Calculate the equilibrium constant, K, for the

asked by antonio on March 31, 2012
6. ### chemistry

An equilibrium mixture of SO2,SO3 and O2 gases is maintained in a 11.5 L flask at a temp at which Kc=55.2 for the rxn: 2SO2 + O2 2SO3. If the # of moles of SO2 and SO3 are =, how many moles of O2 are present? I let SO2 and SO3 =x

asked by Holly on September 14, 2011
7. ### math

how much oxygen is required to convert total so2 into so3 tell me the percentage ratio of so2:o2 the reaction is so2+1/2o2=so3

asked by himanshu dave on October 15, 2012
8. ### Chemistry

An equilibrium mixture at 852 K is found to contain 3.61 x 10^ - 3 mol/L SO3. Calculate the equililbrium , constant , keq for the reaction where SO2 an O2 are reactants and SO3 is the produce.

asked by Ana on May 12, 2010
9. ### Chemistry

Without detailed equilibrium calculations, estimate the equilibrium concentration of SO3 when a mixture of 0.134 mol of SO2 and 0.067 mol of O2 in a 275 mL flask at 300oC combine to form SO3. 2 SO2(g) + O2(g) = 2 SO3(g) Kc =

asked by Kiba on February 14, 2012
10. ### Chemistry

The equilibrium constant is 16 for the gas phase reaction SO2 + NO2 SO3 + NO at a certain temperature. If 3.0 moles each of SO2 and NO2 are placed together in an empty 1.0 liter flask and the system is allowed to come to

asked by Amanda on April 20, 2014

More Similar Questions