For which project would knowledge of Kepler's laws prove most useful? 1.measuring the distance between Earth and the moon
2. calculating the mass of Earth
3. determining the structure of the solar system's planets
4. putting a communications satellite in Earth orbit

Glass has a hardness that is in the middle of the hardness scale. what is the hardness of glass?

What structural formula represents 4 electrons shared between two atoms?

8.29 two streams containing pyridine and acetic acid at 25°c are mixed and fed into a heat exchanger. due to the heat-of-mixing effect, it is desired to reduce the temperature after mixing to 25°c using a stream of chilled ethylene glycol as indicated in the diagram. calculate the mass flow rate of ethylene glycol needed. the heat capacity of ethylene glycol at these conditions is approximately 2.8 kj/(kg k), and the enthalpy change of mixing (δmixh) is given below.