Which formula represents copper(i) oxide?
(1) cuo (3) cu2o
(2) cuo2 (4) cu2o2

Answer : The correct formula of copper(I) oxide is, (3)

Explanation :

Copper(I) oxide is an ionic compound because copper element is a metal and oxide element is a non-metal. The bond formed between a metal and a non-metal is always ionic in nature.

The nomenclature of ionic compounds is given by:

The charge on copper is (+1) and the the charge on oxide is (-2). The charges are not balanced.  The charges are balanced by the criss-cross method.

Hence, the formula of copper(I) oxide is,

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"