Which is a sign of chemical change A. Ice cream left at room temperature melts
B. Calcium chloride is dissolved in H2O and disappears
C. Paint on a freshly painted wall dries and is no longer sticky
D. When H2S gas is bubbled into a lead acetate solution a precipitate forms

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the correct answer is b. a strong acid completely dissociates to its ions when dissolved in water. completely dissociates to and ions. a is incorrect because does not fully ionize to and ions and some remain as the compound . c and d are incorrect because, and do not fall into the category of bronsted lowry acids. a bronsted lowry acid is a proton donor and since both molecules do not have a proton to donate they are not bronsted lowry acids. likewise,   if we use the lewis acid definition, they cannot be acids. a lewis acid is an electron pair acceptor. both and have a complete octet so can not accept any electrons which disqualifies them as acids.