A type of cold pack has two separate sections inside. One section contains a liquid and the other section contains a powder. When the cold pack is squeezed, the section that holds the liquid breaks. When the liquid combines with the powder, the pack becomes very cold. Which is the best explanation why the temperature of the pack decreases when the liquid and powder combine?

Achemistry student weighs out 0.306 g of citric acid (h3c6h5o7), a triprotic acid, into a 250 ml volumetric flask and dilutes to the mark with distilled water. he plans to titrate the acid with 0.1000 m naoh solution. calculate the volume of naoh solution the student will need to add to reach the final equivalence point. be sure your answer has the correct number of significant digits.