# First Order Reaction

## Trending Questions

**Q.**For a first order reaction A→ Products, initial concentration of A is 0.1 M, which becomes 0.001 M after 5 minutes. Rate constant for the reaction in min–1 is

**Q.**A first order reaction has a rate constant of 2.303×10−3 s−1. The time required for 40 g of this reactant to reduce to 10 g will be:

(Given that log2 =0.3010)

- 230.3 s
- 301 s
- 602 s
- 2000 s

**Q.**

For a first order reaction, show that time required for 99% completion is twice the time required for the completion of 90% of reaction.

**Q.**

A radioactive nucleus decays by two different processes. The half-life for the first process is $10s$ and that for the second is $100s$. The effective half-life of the nucleus is close to:

$55sec$

$6sec$

$12sec$

$9sec$

**Q.**

A first order reaction takes 40 min for 30% decomposition. Calculate t12

**Q.**t1/4 can be taken as the time taken for the concentration of a reactant to drop to 3/4 of its value. If the rate constant for a first order reaction is k, the t1/4 can be written as [ln2 = 0.695, ln = 1.1]

- 0.69 / k
- 0.75 / k
- 0.10 / k
- 0.29 / k

**Q.**

Which of the following graphs is correct for a first order reaction ?

**Q.**Decomposition of H2O2 follows first order kinetics. In fifty minutes, the concentration of H2O2 decreases from 0.5 to 0.125 M in one such decomposition. When the concentration of H2O2 reaches 0.05 M, the rate of formation of O2 will be:

- 6.93×10−4 mol min−1
- 2.66 L min−1 at STP
- 1.34×10−2 mol min−1
- 6.93×10−2 mol min−1

**Q.**The distillation of phenol with zinc dust gives:

- C6H6
- C6H5−C6H5
- C6H12
- C6H5−O−C6H5

**Q.**

Consider a first order gas phase decomposition reaction given below

A(g)→B(g)+C(g) The initial prssure of the system before decomposition of A was pi. After lapse of time 't' total pressure of the system increased by x units and became 'pt'. The rate constant k for the reaction is given as ...... .

(a)k=2.303tlogpipi−x(b)k=2.303tlogpi2pi−pt(c)k=2.303tlogpi2pi+pt(d)k=2.303tlogpipi−x

**Q.**The rate constant for a first order reaction is 6.93×10−3 s−1. The Half-life period of the reaction is:

- 10 s
- 10000 s
- 1000 s
- 100 s

**Q.**

What is the rate law for a first-order reaction?

**Q.**

A first order reaction is 50% completed in 1.26×1014s. How much time would it take for 100% completion ?

(a)1.26×1015s(b)2.52×1014s(c)2.52×1028s(d)Infinite

**Q.**

If 60% of a first order reaction was completed in 60 minutes, 50% of the same reaction would be completed in approximately

- 40 min
- 50 min
- 60 min
- 45 min

**Q.**For a first order reaction, A(g)→2B(g)+C(g), the rate constant in terms of initial pressure P0 and pressure at time t(Pt), is given by:

- 1tlnP0Pt−P0
- 1tln3P0Pt−P0
- 1tln3P03Pt−P0
- 1tln2P03P0−Pt

**Q.**

Give the unit of Rate Constant of a Reaction.

**Q.**

The atomic mass of silver found in nature is $\mathrm{Ar}\left(\mathrm{Ag}\right)=107.983$. This silver is made of $107\mathrm{Ag}$ and $109\mathrm{Ag}$ Isotopes. Calculate the proportion of the mass of $107\mathrm{Ag}$ isotope which is in natural silver atoms.

**Q.**

Sucrose decomposes in acid solution into glucose and fructose according to the first order rate law, with t12=3.00h. What fraction of sample of sucrose remains after 8h?

**Q.**

The results given in the below table were obtained during kinetic studies of the following reaction: 2A + B â†’ C + D

X and Y in the given table are respectively :

0.4, 0.4

0.3, 0.4

0.4, 0.3

0.3, 0.3

**Q.**One atmosphere is numerically equal to approximately

10

^{6}dynes cm^{-2}10

^{2}dynes cm^{-2}10

^{4}dynes cm^{-2}10

^{8}dynes cm^{-2}

**Q.**Thermal decomposition of a compound is of first order. If 50% of a sample of the compound is decomposed in 120 minutes, how long will it take for 90% of the compound to decompose ?

- 120 min
- 299 min
- 399 min
- 320 min

**Q.**The kinetic study of hydrolysis of ethyl acetate is catalysed by an acid, and is followed by titrating a fixed volume of a reaction mixture with a standard alkali solution, at different intervals of time. The ester hydrolysis is acid catalysed. V0, Vt and V∞ are the volumes of alkali required at t = 0, t = t and t=∞ respectively. Then, match the statements given in Column I with those in Column II.

Column IColumn IIa)V0 is proportional top) Total concentrations of acid initiallypresent and concentration of acidformed at time t.b)Vt is proportional toq) Concentration of acid initiallypresent as the catalystc)(V∞−Vt) is proportional tor) Concentration of acid formed afterthe completion of reactiond)(V∞−V0)is proportional tos) Concentration of ester remainingat time t.

- (a-q, b-p, c-s, d-r)
- (a-p, b-p, c-s, d-r)
- (a-q, b-q, c-s, d-r)
- (a-q, b-q, c-r, d-s)

**Q.**

In the reaction, P + Q ⟶ R + S

the time taken for 75% reaction of P is twice the time taken for 50% reaction of P. The concentration of Q varies with reaction time as shown in the figure. The overall order of the reaction is

- 0
- 1
2

- 3

**Q.**

Consider a certain reaction; A → products with k=2.0×10−2s−1. Calculate the concentration of A remaining after 100 s, if the initial concentration of A is 1.0 mol L−1.

**Q.**The rate constant of a first order reaction is 6.93×10−3 min−1. If we start with 10 mol/L, it is reduced to 1.25 mol/L in:

- 100 minutes
- 200 minutes
- 300 minutes
- 30 minutes

**Q.**

Calculate the following:

Number of molecules of ${\mathrm{CH}}_{4}$ in 80.0 g of it.

**Q.**The rate of a first order reaction R→Pis 7.5×10−4molL−1s−1 when the concentration of R is 0.5 mol L−1.

The rate constant is

- 4.16×10−7s−1
- 2.5×10−5s−1
- 1.5×10−5s−1
- 1.5×10−3s−1

**Q.**Given that for a reaction of order , the integrated form of the rate equation is k=1t(n−1)∣∣∣1Cn−1−1Cn−10∣∣∣

where C0 and C are the values of the reactant concentration at the start and after time t . What is the relationship between t3/4 and t1/2where t3/4 is the time required for to become 14C0?

- t3/4=t1/2[2n−1+1]
- t3/4=t1/2[2n−1−1]
- t3/4=t1/2[2n+1−1]
- t3/4=t1/2[2n+1+1]

**Q.**For a first order reaction, t0.75 is 138.6 seconds. Its specific rate constant (in s−1) is:

- 10−2
- 10−4
- 10−5
- 10−6

**Q.**In the following reaction

A→B+C, rate constant is 0.001 M/s. If we start with 1 M of A, the concentration of A and B after 10 min are respectively:

- 0.5M, 0.5M
- 0.4M, 0.6M
- 0.6M, 0.4M
- None of these