A metal sample is hammered into a rectangular sheet with an area of 31.2 ft2 and an average thickness of 2.30 x 10-6 cm. If the density of this sample is 7.15 g/cm3, calculate the mass of the sample in grams (g).

0.09 moles of sodium sulfate in 12 ml of solution

Select the correct value for the indicated bond angle in each of the compounds. o−o−oo−o−o angle of o3 90° 109.5° < 109.5° 120° < 120° 180° f−b−ff−b−f angle of bf3 180° < 109.5° < 120° 120° 109.5° 90° f−o−ff−o−f angle of of2 < 120° 120° 90° 109.5° 180° < 109.5° cl−be−clcl−be−cl angle of becl2 90° 109.5° 180° 120° < 109.5° < 120° f−p−ff−p−f angle of pf3 90° 109.5° < 109.5° 180° 120° < 120° h−c−hh−c−h angle of ch4 90° < 109.5° 180° 120° < 120° 109.5°

Describe at least two advantages and two disadvantages of using hydropower as a source of energy.