If it takes 30 seconds for a reactant concentration to decrease from 1.0 M to 0.5 M in a first-order chemical reaction, then what is the rate constant for the reaction?

A. 0.033 s^–1
B. 0.046 s^–1
C. 0.023 s^–1
D. 43 s^–1

Question

If it takes 30 seconds for a reactant concentration to decrease from 1.0 M to 0.5 M in a first-order chemical reaction, then what is the rate constant for the reaction?

 		A.	0.033 s^–1
 		B.	0.046 s^–1
 		C.	0.023 s^–1
 		D.	43 s^–1

vera_ewing · Answer

@JFraser help please!

jfraser · Answer

look at the pieces you know;

you know the change in time (30s)

you know the change in concentration (1.0M - 0.5M)

you know the reaction is first-order

vera_ewing · Answer

Okay, so what does it look like when the numbers are plugged into the equation?

jfraser · Answer

$$rate = \frac{\Delta [reactant]}{\Delta time} = k*[reactant]^1$$

jfraser · Answer

don't care about the numbers

vera_ewing · Answer

Ohh so I got 0.0327. What did you get?

jfraser · Answer

that's about it

vera_ewing · Answer

Would I just say A for the answer?

vera_ewing · Answer

The answer is C.

anonymous · Answer

got the answer but a confusion between use of order and mole.what is the general formula?