Question

The ratio by mass for calcium and oxygen in calcium oxide is given 5:2. Calculate the ratio by number of atoms for calcium oxide (Atomic mass of Ca = 40u, O = 16u).

Write the chemical formula of calcium oxide.

Answer 1

Given:
          Ratio by mass for calcium and oxygen = 5 : 2
       
  Atomic mass of Calcium = 40u 
  
  Atomic mass of oxygen = 16u

 calcium ⇒mass ratio / atomic = $\frac{5}{40}$ = $\frac{1}{8}$

oxygen ⇒ mass ratio / atomic = $\frac{16}{2}$ = $\frac{1}{8}$


Simplest ratio of atoms = $\frac{ \frac{1}{8} }{ \frac{1}{8} }$
 
                                    = 1:1

Chemical formula of calcium oxide = CaO

Answer 2

see attachment...... I hope it will help u