An endothermic double replacement reaction is a chemical reaction in which two reactants exchange ions to form two new products, and energy is absorbed from the surroundings in the form of heat. A general chemical equation for an endothermic double replacement reaction is:

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AB + CD → AD + CB + energy

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In this equation, A and B represent the atoms or ions that are exchanged between reactants AB and CD, and C and D represent the atoms or ions that remain unchanged. The arrows indicate that the reaction proceeds in both directions, but in the endothermic case, the forward reaction is favored over the reverse reaction at equilibrium.