Question

6. If concentrations measured in moles per liter, and time in seconds, what are the units of the rate constant for (a) a first order reaction, (b) a second-order reaction, and (c) a third-order reaction

Answer 1

Answer:

The rate constant has units of

a) s⁻¹ or /s for a first order reaction.

b) /sM or (s⁻¹M⁻¹) or (L/s.mol) or (L.s⁻¹mol⁻¹) for a second order reaction.

c) /sM² or s⁻¹M⁻² or (L²/s.mol²) or (L².s⁻¹mol⁻²) for a third order reaction.

Explanation:

The rate of a chemical reaction is defined as the amount (in concentration terms) of reactant used up or products formed per unit time. It's units generally is given in the units of concentration per unit time.

Rate = M/s or written extensively as mol/L/s = mol/L.s

And for all types of orders of reactions, the rate of reaction is given as

Rate = kCⁿ

k = Reaction rate constant

C = concentration of specie involved in the reaction

where n is the order of reaction.

Note that the units of the rate of the reaction still has to be mol/L.s or M/s regardless of its order.

M = mol/L

a) For a first order reaction

Rate = kC

M/s = k × M

K = (1/s)

Hence, the rate constant has a unit of /s or s⁻¹

b) Second order reaction

Rate = kC²

M/s = k × M²

k = (1/Ms)

Units of /sM or s⁻¹M⁻¹ or (L/s.mol)

c) Third order reaction

Rate = kC³

M/s = k × M³

k = (1/sM²)

Units of /sM² or s⁻¹M⁻² or (L²/s.mol²)

Hope this Helps!!!

Answer 2

Answer:

(a) a first order reaction = s^-1.

(b) a second-order reaction = L(mol·s)

(c) a third-order reaction = s⁻¹M⁻²

Explanation:

Okay, this question is a question that has to do with kinetics that is how reaction occurs.

So, the RATE LAW is one of the concept that is being used in determining conditions of chemical reactions. The relationship between the the reactants molarity and the reaction rate is known as rate law. That is to say;

Rate law = K × Molarity.

So, In this question we are given that the concentrations measured in moles per liter, and time in seconds.

The FIRST ORDER REACTION has its unit for rate constant as per seconds(s^-1).

That is from; Rate law = k

Molarity/s = k × Molarity.

k = s^-1

(b) a second-order reaction;

Rate law= k × (molarity)^2.

Molarity/s = k × (Molarity)^2.

k = L(mol·s)

(c) A third-order reaction = s⁻¹M⁻²

Same thing applies.