Visitors to the Grand Canyon are often surprised by the silence and stillness they experience as they make their way down into the canyon. At some
spots, where the Colorado River winds slowly through the canyon, it is
more than 1,800 m deep. With a partner, discuss how the changes you
observed in the video relate to the Grand Canyon. Record your thoughts
and reasoning below.

Calculate the number of kilojoules to warm 125 g of iron from 23.5°c to 78.0°c.

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°

What is the value of the standard enthalpy of formation of an element in its most stable form?