A 45.90 g sample of pure copper is heated in a test tube to 99.40°C. The copper sample is then transferred to a calorimeter containing 61.04 g of deionized water. The water temperature in the calorimeter rises from 24.43°C to 29.10°C.

Two friends at different locations want to communicate with each other by sending low energy signals. which of the following methods can they use to communicate? a) produce x-rays using colliding electrons and send them to radios, which capture sound b) send messages using infrared radiation, which travel in the form of waves c) send radio waves through intervening media like radio and television d) produce sound waves using microwaves from heated objects

Assuming complete dissociation of the solute, how many grams of kno3 must be added to 275 ml of water to produce a solution that freezes at -14.5 c? the freezing point for pure water is 0.0 c and k_f is equal to 1.86 c/m

8. what happens to matter during a chemical reaction