5g of calcium combine with 2g of oxygen to form a compound. Find the molecular formula of the compound. (Atomic mass of Ca=40u;O=16u).
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Dear Student,

Please find below the solution to the asked query:

number of moles in 5 g of calcium = mass /  molar mass

= (5 / 40) =  0.125

number of moles in 2 g of oxygen = mass / molar mass

= (2 / 16)

= 0.125

Now we will calculate the simplest ratio of the element by dividing the number of moles of each element by the smallest value. Since number of moles of each element is 0.125, therefore calcium and oxygen are present in a ratio of 1 : 1. Thus the empirical formula of the compound is CaO. For calculating the molecular formula, we need the molecular mass of the compound. However, because a compound with the formula CaO is known, therefore the molecular formula of the compound is CaO.

Hope this information clears your doubts about the topic.

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