You take 200. g of a solid at 30.0 °C and let it melt in 400. g of water initially at 85.1 °C. The water's temperature decreases from 85.1 °C to 30.0 °C. What is the heat of fusion of this solid?

I don't know I to do this problem

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.

answer: any goods being imported from another country may be subject to issued by the federal government are tariffs

explanation:  

tariffs are a tax on anything that are imported from abroad. government use them to protect and boost their local industries and the thought is that they encourage consumers to buy local instead of importing and they will hope will protect jobs and economy in the country that implements them