$CH_3-CH_2-CH=O$ $\xrightarrow[(2) H^{+}]{(1) \text{Tollen's reagent}} X$ $\xrightarrow[(2) \text{dry distillation}]{(1) Ca(OH)_2} Y$
$Y$ is:

Ethyl chloride reacts with sodium ethoxide to form a compound $A$. Which of the following reactions also yields $A$?

Among $Ni(CO)_4$,$[Ni(CN)_4]^{2-}$ and $[NiCl_4]^{2-}$,which of the following statements is correct regarding their magnetic properties?

Given that:
$2C_{(s)} + 2O_{2(g)} \to 2CO_{2(g)}; \Delta H = -787 \ kJ$
$H_{2(g)} + 1/2 O_{2(g)} \to H_2O_{(l)}; \Delta H = -286 \ kJ$
$C_2H_{2(g)} + 2.5 O_{2(g)} \to 2CO_{2(g)} + H_2O_{(l)}; \Delta H = -1301 \ kJ$
Calculate the heat of formation of acetylene $(C_2H_{2(g)})$ in $kJ$.

An object $2.4 \; m$ in front of a lens forms a sharp image on a film $12 \; cm$ behind the lens. $A$ glass plate $1 \; cm$ thick,of refractive index $1.50$ is interposed between the lens and the film with its plane faces parallel to the film. At what distance (from the lens) should the object be shifted to be in sharp focus on the film (in $; cm$)?

The taxonomic unit $phylum$ in the classification of animals is equivalent to which hierarchical level in the classification of plants?