Question

question 10
1 pts
a metal (m) forms an oxide with the formula mo. if the oxide contains 39.70% o by mass, what is the identity of m?
hint
first, assume 100 grams of sample and calculate the number of moles of oxygen.
next, use the molar ratio indicated by the formula (1:1) to determine the number of moles of m.
now, given the number of moles of m and the mass of m, calculate the molar mass to determine the identity of m.
magnesium
molybdenum
tungsten
iron

Explanation:

Step1: Calculate moles of oxygen

Assume 100g of the oxide. Mass of O = 39.70g. Molar mass of O is \(M_O=16\space g/mol\).
Number of moles of \(O,n_O=\frac{m_O}{M_O}=\frac{39.70\space g}{16\space g/mol}=2.48125\space mol\)

Step2: Determine moles of M

From the formula \(MO\), molar ratio of \(M:O = 1:1\). So \(n_M=n_O = 2.48125\space mol\)

Mass of \(M,m_M=(100 - 39.70)\space g=60.3\space g\)

Step3: Calculate molar mass of M

Molar mass of \(M,M_M=\frac{m_M}{n_M}=\frac{60.3\space g}{2.48125\space mol}\approx24.3\space g/mol\)

Answer:

magnesium