D
A describes liquid, b describes solid, and c describes solid as well. therefore d is the only good answer
B)False
because photons dont have mass
Answer: The equilibrium will shift to the left to favor the reverse reaction.
Explanation:
This is a direct application of Le Chatelier's principle.
Le Chatelier's principle predicts that if a chage is introduced in a system in equilibrium, the system will react to compensate the change.
The increase in the concentration of CO, which is in the right side of the chemical equation, takes the system out of the equilibrium.
Chemically, the greater number of molecules of CO means that more CO will react to favor the reverse reaction and restore the equilibrium with the increase of molecules in the left side (CH4 and H2O).
Answer: The given quantity is 2 moles of magnesium or 48 g of magnesium.
The unknown quantity is mass of MgO in grams.
Molar mass of MgO = 40 g
Explanation: 
As can be seen from the chemical equation, 2 moles of magnesium react with 1 mole of oxygen gas to give 2 moles of MgO.
According to mole concept, 1 mole of every substance weighs equal to its molar mass.
Thus 
of magnesium produce=
of MgO.
Molar mass is the mass in grams of 1 mole of the substance.
Thus if 2 moles of MgO weigh= 80 g
1 mole of MgO will weigh=
Thus molar mass of MgO is 40 g.
