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) 

• 230.3 minutes

• 23.03 minutes

• 46.06 minutes

• 46.06 minutes

Solid Ba (NO₃)₂ is gradually dissolved in a 1.0x 10⁻⁴ × Na₂CO₃ solution. At what concentration of Ba²⁺ will a precipitate begin to form?(K_sp for BaCO₃ = 5.1 ×10⁻⁹  )

• 4.1 x 10^-5 M

• 5.1 x 10^-5 M

• 8.1 x 10^-8 M

• 8.1 x 10^-8 M

For a reaction 1/2A →2B, rate of disappearance of ‘A’ is related to the rate of appearance of ‘B’ by the expression

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 a catalyst lowers the activation energy of both (forward and reverse) reactions by 100 kJ mol^–1. The enthalpy change of the reaction (A₂ + B₂ → 2AB) in the
presence of catalyst will be (in kJ mol^–1) –

• 300

• 120

• 280

• 280

Consider the reaction, 2A + B → Products. When the concentration of B alone was doubled, the half-life did not change. When the concentration of An alone was doubled, the rate increased by two times. The unit of rate constant for this reaction is –

• L mol^–1 s^–1

• no unit

• mol L^–1s^–1

• mol L^–1s^–1

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 ?

• 1000 days

• 300 days

• 50 days

• 50 days

Which of the following nuclear reactions will generate an isotope?

• neutron particle emission

• positron emission

• α-particle emission

• α-particle emission

A reaction was found to be second order with respect to the concentration of carbon monoxide. If the concentration of carbon monoxide is doubled, with everything else kept the same, the rate of reaction will

• remain unchanged

• triple

• increase by a factor of 4

• increase by a factor of 4

In the transformation of  , if one emission is an α-particle, what should be the other emission(s)?

• Two β^–

• Two β^– and one β⁺

• One β^– and one γ

• One β^– and one γ

In Langmuir’s model of adsorption of a gas on a solid surface

• the rate of dissociation of adsorbed molecules from the surface does not depend on the surface covered

• the adsorption at a single site on the surface may involve multiple molecules at the same time

• the mass of gas striking a given area of the surface is proportional to the pressure of the gas

• the mass of gas striking a given area of the surface is proportional to the pressure of the gas