The alkali metals have relatively low melting point. Which one of the following alkali metals is expected to have the highest melting point?

Consider the following reaction,

$$C{H_4}(g) + {H_2}(g)\buildrel {1270\,K} \over \longrightarrow CO(g) + 3{H_2}(g)$$

In the reaction given above, the mixture of CO and H₂ is

Addition of gypsum to cement

To weld metals together, high temperature is required. Such a high temperature is obtained by burning