The radionucleide $${}_{90}^{234}Th$$ undergoes two successive $$\beta$$ -decays followed by one $$\alpha$$-decay. The atomic number and the mass number respectively of the resulting radionucleide are

For the reaction system:

2NO(g) + O₂(g) $$\to$$ 2NO₂(g) volume is suddenly reduce to half its value by increasing the pressure on it. If the reaction is of first order with respect to O₂ and second order with respect to NO, the rate of reaction will

In respect of the equation k = Ae^-E_a/RT in chemical kinetics, which one of the following statements is correct?

The half-life of a radioactive isotope is three hours. If the initial mass of the isotope were 256 g, the mass of it remaining undecayed after 18 hours would be