If the initial concentration of H2O2 is 3.62×10-2 M, the concentration of H2O2 will be _____ M after 1235 min have passed.

Question

The decomposition of hydrogen peroxide in dilute sodium hydroxide at 20 °C

H₂O₂(aq)  H₂O(l) + ½ O₂(g)

is first order in H₂O₂ with a rate constant of 1.10×10^-3 min^-1.

If the initial concentration of H₂O₂ is 3.62×10^-2 M, the concentration of H₂O₂ will be _____  M after 1235 min have passed.

The gas phase decomposition of sulfuryl chloride at 600 K

SO₂Cl₂(g)SO₂(g) + Cl₂(g)

is first order in SO₂Cl₂ with a rate constant of 2.80×10^-3 min^-1.

If the initial concentration of SO₂Cl₂ is 3.62×10^-3 M, the concentration of SO₂Cl₂ will be 7.86×10^-4 M after________ min have passed.

Answer 1

For a first order reaction...

ln [A] = -kt + ln [A]_o

plug in the values and solve for [A]

ln [A] = (-1.10x10^-3 min^-1)(1235 min) + ln 3.62x10^-2) = (-1.36) + (-3.32) = -4.68

[A] = [H2O2] = 9.28x10^-3 M

For the second question, use the same equation as above for first order reaction, and solve for t, time.