Why does the heart rate increase when you exercise?

What is the chemical formula of the following compound

8.98 dm3 of hydrogen gas is collected at 38.8 °c. find the volume the gas will occupy at -39.9 °c if the pressure remains constant.

Harry lives in a city, and he has a lung condition known as asthma. on certain days, harry has to stay inside because pollutants in the air make it difficult for him to breathe. which of these pollution sources are nonpoint sources that might bother harry if he goes outside? choose the two that apply.