We know that
1) empirical formula of a compound is the representation of a molecules with the elements in simplest mole ratio.
2) the molar mass is the actual proportion of moles of elements present in a molecule
3) there is a simple ratio between the molar mass and empirical mass a molecule
Now let us solve each problem
1) empirical formula of
will be
![CuO_(2)](https://img.qammunity.org/2020/formulas/chemistry/middle-school/xb9firl04ez3v3vhcfqmv3hfbjtejntkz7.png)
2) empirical formula of
will be
![Zn_(3)(NO_(3))_(4)](https://img.qammunity.org/2020/formulas/chemistry/middle-school/rybl8rg816vyrgg20x2twm0ajvu82j8mgq.png)
3) empirical formula of
will be
![Ti_(4)S_(5)](https://img.qammunity.org/2020/formulas/chemistry/middle-school/e0j5dv1ucmwbphssrxswr0ne1gqi74e2jo.png)
4) the molecular formula will be :
![Ratio=(molarmass)/(empiricalformula)=(112.04)/(28.01)=4](https://img.qammunity.org/2020/formulas/chemistry/middle-school/e5ahf8diyx4bzk2w3uaq9l5o0z7gn9au2v.png)
the molecular formula = 4 X empirical formula = 4 X CO =
![C_(4)O_(4)](https://img.qammunity.org/2020/formulas/chemistry/middle-school/1j8951jh25ze4dl2npajjlhszuj9vmcc1s.png)
5) the mole ratio of Cl and Cr is
![(1.90)/(0.631)=3](https://img.qammunity.org/2020/formulas/chemistry/middle-school/inl4v16v0snqv2nwksli59avx6zh1yub6d.png)
empirical formula will be
![CrCl_(3)](https://img.qammunity.org/2020/formulas/chemistry/middle-school/ttlktiiux1bpbag7jp8io6sqwimofjkkua.png)