Identify the correct statements about alkali metals.

A. The order of standard reduction potential (M$$^+$$ | M) for alkali metal ions is Na > Rb > Li.

B. CsI is highly soluble in water.

C. Lithium carbonate is highly stable to heat.

D. Potassium dissolved in concentrated liquid ammonia is blue in colour and paramagnetic.

E. All the alkali metal hydrides are ionic solids.

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Match List I with List II

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Reaction of BeO with ammonia and hydrogen fluoride gives A which on thermal decomposition gives $$\mathrm{BeF_2}$$ and $$\mathrm{NH_4F}$$. What is 'A'?

Portland cement contains 'X' to enhance the setting time. What is 'X'?