Number of moles = mass of product / molecular mass =mass of product (MgO) / 40.3
Since the mass of MgO is not given in the question, the correct answer choice cannot be given. However, proceeding witht eh above formula will enable you to find the correct number of moles given the mass of MgO.
Some of the liquid surface particles may gain enough KE to escape into the space above the liquid - evaporate. ... The kinetic molecular theory states that all matter is made up tiny constantly moving particles and in a solid they are packed tightly. (Only answered part of the question, sorry bro)