List of top Chemistry Questions

The plot of log 𝑘_𝑓 versus $\frac{1}{T}$ for a reversible reaction, A (g) ⇌ P (g) is shown.

plot of log 𝑘𝑓 versus 1/T for a reversible reaction

Pre-exponential factors for the forward and backward reactions are 10¹⁵s^-1 and 10¹¹s^-1 respectively. If the value of log K for the reaction at 500 K is 6, the value of |log kb| at 250K is_________
[K = equilibrium constant of the reaction,
𝑘_𝑓 = rate constant of forward reaction,
𝑘_𝑏 = rate constant of backward reaction]

The reaction of 4-methyloct-1-ene (P, 2.52 g) with HBr in the presence of (C₆H₅CO)₂O₂ gives two isomeric bromides in a 9 : 1 ratio, with a combined yield of 50%. Of these, the entire amount of the primary alkyl bromide was reacted with an appropriate amount of diethylamine followed by treatment with aq. K₂CO₃ to give a non-ionic product S in 100% yield. The mass (in mg) of S obtained is ___. [Use molar mass (in g mol^–1): H = 1, C = 12, N = 14, Br = 80]

For He⁺, a transition takes place from the orbit of radius 105.8 pm to the orbit of radius 26.45 pm. The wavelength (in nm) of the emitted photon during the transition is ___.
[Use: Bohr radius, a = 52.9 pm, Rydberg constant, 𝑅H = 2.2 × 10⁻¹⁸ J, Planck’s constant, h = 6.6 × 10⁻³⁴ J s, Speed of light, c = 3 × 10⁸ m s⁻¹]

In a one-litre flask, 6 moles of A undergoes the reaction A (g) ⇌ P (g). The progress of product formation at two temperatures (in Kelvin), T₁ and T₂, is shown in the figure:

If T₁ = 2T₂ and (∆G₂^Θ − ∆G₁^Θ) = RT₂ ln x, then the value of x is ___ .
[∆G₁^Θ and ∆G₂^Θ are standard Gibb’s free energy change for the reaction at temperatures T₁ and T₂, respectively.]

Consider the following molecules: Br₃O_8, F₂O, H₂S₄O₆, H₂S₅O₆, and C₃O_2. Count the number of atoms existing in their zero oxidation state in each molecule. Their sum is____.

H₂S (5 moles) reacts completely with acidified aqueous potassium permanganate solution. In this reaction, the number of moles of water produced is x, and the number of moles of electrons involved is y. The value of (x + y) is ____.

Predict the major product in the following reaction:

A current of 15.0 amperes is passed through a solution of CrCl2, for 45 minutes. The volume of Cl₂ , (in I) obtained at the anode at 1 atm and 273 K is around (IF=96500 Cmol-1, At. wt. of Cl=35.5, R=0.082 L-atmK^-1 mol^-1)

Pick out the incorrect statement(s) from the following.

1. Glucose exists in two different crystalline forms, $ \alpha $-D-glucose and $ \beta $-D-glucose.
2. $ \alpha $-D-glucose and $ \beta $-D-glucose are anomers.
3. $ \alpha $-D-glucose and $ \beta $-D-glucose are enantiomers.
4. Cellulose is a straight chain polysaccharide made of only $ \beta $-D-glucose units.
5. Starch is a mixture of amylase and amylopectin, both contain unbranched chain of $\alpha$-D-glucose units.