Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Chemical Kinetics and Nuclear Chemistry question

2010 · Shift 0 · Q18
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Chemistry
  4. /Chemical Kinetics and Nuclear Chemistry
  5. /2010 · Shift 0 · Q18

Chemical Kinetics and Nuclear Chemistry question

2010 · Shift 0 · Q18

JEE MainChemistryChemical Kinetics and Nuclear ChemistryMCQ+4 / −1
The time for half life period of a certain reaction A →\to→ products is 1 hour. When the initial concentration of the reactant ‘A’, is 2.0 mol L–1, how much time does it take for its concentration to come from 0.50 to 0.25 mol L–1 if it is a zero order reaction ?
  1. A
    4 h
  2. B
    0.5 h
  3. C
    0.25 h
  4. D
    1 h
View written solutionFree

Correct answer: C

  1. Use the half-life formula for a zero-order reaction

For a zero-order reaction, [A]t=[A]0−kt[A]_t = [A]_0 - kt[A]t​=[A]0​−kt

and the half-life is t1/2=[A]02kt_{1/2} = \frac{[A]_0}{2k}t1/2​=2k[A]0​​

  1. Find the rate constant using the given half-life

Given:

  • Initial concentration for the half-life statement: [A]0=2.0 mol L−1[A]_0 = 2.0\,\text{mol L}^{-1}[A]0​=2.0mol L−1
  • Half-life: t1/2=1 ht_{1/2} = 1\,\text{h}t1/2​=1h

So, 1=2.02k=1k1 = \frac{2.0}{2k} = \frac{1}{k}1=2k2.0​=k1​

Hence, k=1 mol L−1h−1k = 1\,\text{mol L}^{-1}\text{h}^{-1}k=1mol L−1h−1

  1. Calculate the time for concentration to decrease from 0.50 to 0.25 mol L−1^{-1}−1

For zero-order kinetics, t=[A]1−[A]2kt = \frac{[A]_1 - [A]_2}{k}t=k[A]1​−[A]2​​

Here,

  • [A]1=0.50 mol L−1[A]_1 = 0.50\,\text{mol L}^{-1}[A]1​=0.50mol L−1
  • [A]2=0.25 mol L−1[A]_2 = 0.25\,\text{mol L}^{-1}[A]2​=0.25mol L−1
  • k=1 mol L−1h−1k = 1\,\text{mol L}^{-1}\text{h}^{-1}k=1mol L−1h−1

Thus, t=0.50−0.251=0.25 ht = \frac{0.50 - 0.25}{1} = 0.25\,\text{h}t=10.50−0.25​=0.25h

  1. Check options
  • A: 4 h4\,\text{h}4h
  • B: 0.5 h0.5\,\text{h}0.5h
  • C: 0.25 h0.25\,\text{h}0.25h
  • D: 1 h1\,\text{h}1h

So the correct option is C.

PreviousNext

More from Chemical Kinetics and Nuclear Chemistry

  • Consider the reaction : Cl2​(aq) + H2​S(aq) → S(s) + 2H+ (aq) + 2Cl− (aq) The rate equation for this reaction is rate = k [Cl2​] [H2​S] Which of these mechanisms is/are consistent with this rate equation? (A) Cl2​ +…2010 · MCQ
  • The half life period of a first order chemical reaction is 6.93 minutes. The time required for the completion of 99% of the chemical reaction will be (log 2=0.301) :2009 · MCQ
  • For a reaction 21​A→2B rate of disappearance of ‘A’ is related to the rate of appearance of ‘B’ by the expression2008 · MCQ
  • Which of the following nuclear reactions will generate an isotope?2007 · MCQ
  • A radioactive element gets spilled over the floor of a room. Its half-life period is 30 days. If the initial activity is ten times the permissible value, after how many days will it be safe to enter the room?2007 · MCQ
  • Consider the reaction, 2A + B → products. When concentration of B alone was doubled, the half-life did not change. When the concentration of A alone was doubled, the rate increased by two times. The unit of rate constant for this…2007 · MCQ
  • The energies of activation for forward and reverse reactions for A2​ + B2​ ⇋ 2AB are 180 kJ mol−1 and 200 kJ mol−1 respectively. The presence of catalyst lowers the activation energy of both (forward and reverse)…2007 · MCQ
  • Rate of a reaction can be expressed by Arrhenius equation as: k=Ae−E/RT In this equation, E represents2006 · MCQ