A sample of carbon dioxide (CO2) has a mass of 52.0g. How many oxygen atoms are present?

7.11 x 10²³ atoms of oxygen

Explanation:

Given parameters:

Mass of Carbon dioxide  = 52g

Unknown:

Number of oxygen atoms present = ?

Solution:

To solve this problem, we need to first find the mass of oxygen in the compound.

 Molar mass of CO₂   = 12 + 2(16)  = 44g/mol

 Mass of oxygen  = x 52  = 37.8g

  Number of moles of oxygen  =    =    = 1.18moles

So;

       1 mole of a substance contains  6.02 x 10²³ atoms

1.18 mole of oxygen will contain 1.18 x 6.02 x 10²³ = 7.11 x 10²³ atoms of oxygen

"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"