Identify each of the following catalysts as homogeneous or heterogeneous. Consider the reaction of ethylene and hydrogen in the presence of solid nickel, producing ethane:

a. Nickel is a(n) catalyst.
b. Manganese(IV) oxide is a(n) catalyst.

Who is better, messi or cristiano, i need this for a chemistry class. asap

Put these processes of the water cycle in the correct order, starting at the point where the water is in the lake: 1. water evaporates into the atmosphere 2. rain, snow, or other precipitation falls 3. water collects into larger bodies of water 4. water vapor condenses into liquid water

In the following table, all the columns for the element calcium are filled out correctly. element electron structure of atom electron structure of ion net ionic charge calcium 1s22s22p63s23p64s2 1s32s22p63s23p64s1 +1 true false