A black solid is heated in a tube that is completely evacuated of air. Hydrogen is added to the tube. An orange powder is formed and water vapor is seen on the outside of the tube. Is the original solid an element or compound? Can you identify the chemical?

The black solid is a compound and not an element. My best guess would be the black solid is Hg2O and the orange powder is HgO.

To determine whether the original solid is an element or compound, we need to analyze the information provided.

Firstly, heating the black solid in a tube that is completely evacuated of air suggests that a chemical reaction is taking place. This implies that the black solid is likely a compound since elements do not typically undergo chemical reactions under these conditions.

Next, when hydrogen is added to the evacuated tube, an orange powder is formed. This suggests that a reaction has occurred between the black solid and hydrogen. The fact that a new substance, the orange powder, is generated indicates a chemical change has taken place.

Lastly, the observation of water vapor on the outside of the tube provides further evidence of a chemical reaction. Water vapor is the result of hydrogen (from the hydrogen gas) reacting with another substance (the black solid) and forming water.

Based on these observations, we can conclude that the original black solid was most likely a compound that reacted with hydrogen to produce the orange powder and water vapor. Without additional information, it is difficult to identify the specific chemical involved. More details about the reaction and the black solid would be needed for accurate identification.