Which represents an endothermic reaction

Idon’t understand this page, can someone ?

How many moles of al3+ ions are in 1.25 moles of al2o3

Give the set of reactants (including an alkyl halide and a nucleophile) that could be used to synthesize the following ether: draw the molecules on the canvas by choosing buttons from the tools (for bonds and charges), atoms, and templates toolbars, including charges where needed. ch3ch2och2ch2chch3 | ch3