Additional Exercise 4.32 A 500.0-g piece of iron is heated in a flame and dropped into 400.0 g of water at 10.0 °C. The temperature of the water rises to 90.0 °C. How hot was the iron when it was first removed from the flame?

The answer to that would be magnesium

Self-ionizes to form an equilibruium system in which [ h_{3} o^{+} ]=[ oh^{-} ]=10^{-7} m

Vander waals forces are inter molecular bonds that exist within molecules of the same substance. a water molecule is made up of oxygen and hydrogen atoms which share electrons between each other. the vander waals forces are forces that exist between multitude of different  molecules of water. dipole dipole forces is the type of vander waals force that exist in water. the oxygen atom which is more electronegative pulls the shared electron closer to itself thus generating a partial negative charge while the hydrogen acquire a partial positive charge. these two different charges causes attraction to occur in water molecules.

It would be c. risk.