Certain metal oxide has the formula MO where M denotes the metal. A 73.35-g sample of the compound is strongly heated in an atmosphere of hydrogen to remove oxygen as water molecules. At the end, 64.21 g of the metal is left over. If O has an atomic mass of 16.00 amu, calculate the atomic mass of M and identify the element.

atomic mass 112.4 and Cadmium (Cd)

Explanation:

You have 73.35 g of MO.

After the reaction the O is removed and you only have M which the mass is 64.21 g.

With that you can calculate the mass of O removed:

Mass of O = 9.14 g

Mass = AM * moles; (AM : Atomic Mass)

9.14 = 16 * moles

moles = 9.14 / 16

moles = 0.57125

The formula of the metal oxide is MO, meaning it has 1 mole of M per mole of O. 73.35 had 0.57125 moles of O, then it also had 0.57125 moles of M, and the remaining mass of 64.21 g represents those moles

Mass = AM * moles; (AM : Atomic Mass)

64.21 = AM * 0.57125

AM = 64.21/0.57125 = 112.4 amu

The metal with an atomic mass of 112.4 is Cadmium (Cd), therefore the metal oxide is CdO