When the reaction given below is balanced with the lowest whole number ratio, what is the value of A ? A H2SO4(aq) + B Ca(OH)2(aq) C H2O(l) + ???

Yes, endothermic means it turns cold. and some chemical changes include change of tempature.

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Well you can immediately rule out a and d because if a metal were to lose or gain protons, then it would become a different element all together. the answer here is b because the positive symbol with a number refers to how many electrons the metal can give away to become stable.