The compound in which the number of $d\pi - p\pi$ bonds are equal to those present in $ClO_4^{-}$ is:

$A$ vehicle sounding a whistle of frequency $256 ~Hz$ is moving on a straight road towards a hill with a velocity of $10 ~ms^{-1}$. The number of beats per second observed by a person travelling in the vehicle is (velocity of sound $= 330 ~ms^{-1}$).

Would you expect the second electron gain enthalpy of $O$ to be positive,more negative,or less negative than the first? Justify your answer.

$B(OH)_3 + NaOH \rightleftharpoons NaBO_2 + Na[B(OH)_4] + H_2O$
How can this reaction be made to proceed in the forward direction?

Who discovered lichens?

$x-$ अक्ष के अनुदिश गतिमान एक तरंग का समीकरण $y(x, t) = 0.005 \cos(\alpha x - \beta t)$ द्वारा दिया गया है। यदि तरंग की तरंगदैर्घ्य $0.08 \ m$ और आवर्तकाल $2.0 \ s$ है,तो उपयुक्त इकाइयों में $\alpha$ और $\beta$ के मान क्या होंगे?