# Chemistry

posted by .

The decomposition of ehtane, C_2H_6, is a first-order reaction. It is found that it takes 212seconds to decompose 0.00839M C_2H_6 to 0.00768M.
A. How long in minutes will it take to decompose ethane so that 27% remain
B. What percentage of ethane is decomposed after 22minutes?

• Chemistry -

ln(No/N) = kt
Substitute 0.00839 for No
0.00768 for N and calculate k. Then you can use the same formula for A and B after finding k.
A. I suggest using 100 for No and 27 for N.
B. I suggest using 100 for No, substitute for k and t and solve for N. If you start with 100 then N will be in percent.
Post your work if you get stuck.

• Chemistry -

k- 4.17E-4

A-ln100/27)/4.17E-4
t=52min

B= (ln100/x)=4.17E-4*22
lnx=4.0547
e^94.0547)=57.667
100-57.667 =42%
Thank you

• Chemistry -

I don't obtain k = your number
ln(0.00839/0.00768)= 21k
k = ??

• Chemistry -

The K comes from dividing it by 212seconds

• Chemistry -

I guess it would help if I keyed in the right numbers. The answer to A is OK. I think 27% usually is understood to means 27.0%; however, if it really is 27% then 53% is the right answer; otherwise you would be allowed another s.f. and you could write 52.3 min.

B. Look at B again. If you are using k in seconds, shouldn't you convert k to minutes OR convert 22 min to seconds? You must have done so because the numbers you have don't give 42% but 42% is correct.

• Chemistry -

I converted 22 min into second
-lnx= 4.17E-4 *1320seconds -ln100
lnx=4.0547
x=E^4.0547
x=57.67
100-57.67=42.33%

• Chemistry -

I thought that's what you did but you didn't type it that way the first time. 42%, to two s.f., is correct.

• Chemistry -

Thank you for you help

• Chemistry -

for the same question:

what is the rate of decomposition (in mol/L*hr) when C2H6= 0.00422 M?

## Similar Questions

1. ### Chemistry

Time, (min): 0 10 20 30 Moles,(trans): 1.00 0.90 0.81 0.73 Given the following data, what is the order of the reaction?
2. ### Chemistry

In a first order decomposition reaction, 50% of a compound decomposes in 10.5 min. What is the rate constant of the reaction?
3. ### chemistry

If 10.0 g of CaCO3(s) is heated, 5.61 grams of solid CaO will remain (4.39 g CO2 gas is driven off) If 3.25 g of NaCl(s), which does not undergo decomposition, is mixed with 5.30 g of CaCO3(s) and the mixture is heated long enough …
4. ### chemistry

A reaction is first order and it takes 324 minutes for the reaction to be 50.0% complete. How long will it take for the reaction to be 85.0% complete at the same temperature?
5. ### chemistry

N2O undergoes thermal decomposition at 730°C to nitrogen (N2) and oxygen (O2) via first-order kinetics with a half-life of 3.58 x 103 minutes. Calculate the time required for 90% of a sample of N2O to decompose at 730°C.
6. ### chemistry

If the half-life of a first-order decomposition reaction is 24.2 minutes, how long will it take for 10.0 moles of the reactant to decompose so that only 2.5 mol remains?
7. ### Chemistry

Acetone is one of the most important solvents in organic chemistry, used to dissolve everything from fats and waxes to airplane glue and nail polish. At high temperature, it decomposes in a first order process to methane and ketene …
8. ### Chemistry

At 573 K, gaseous NO2(g) decomposes, forming NO(g) and O2(g). If a vessel containing NO2(g) has an initial concentration of 1.9 × 10−2 mol/L, how long will it take for 75% of the NO2(g) to decompose?
9. ### Chemistry

t takes 572 kJ of energy to decompose 2.00 mol of liquid water. How much energy does it take to decompose 54.0 mol of water?
10. ### chemistry

1. The first order rate constant for the reaction, SO2Cl2(g) → SO2(g) + Cl2(g), is 2.20 x 10-5 s-1 at 593 K. What percent of a sample of SO2Cl2 would be decomposed by heating at 593 K for (a) 1 hr, (b) 3 hr. How long will it take …

More Similar Questions