What's the mass of 7.61 x 10^24 molecules of Magnesium sulfate heptahydrate?
1400 g
1900 g
2500 g
31009

Mass = 3100 g

Explanation:

Given data:

Mass of MgSO₄.7H₂O = ?

Number of molecules = 7.61×10²⁴ molecules

Solution:

First of all we will calculate the number of moles of MgSO₄.7H₂O by using Avogadro number.

1 mole contain 6.022×10²³ molecules

7.61×10²⁴ molecules × 1 mol  / 6.022×10²³ molecules

1.26×10¹ mol

12.6 moles

Mass of MgSO₄.7H₂O:

Mass = number of moles × molar mass

Molar mass of MgSO₄.7H₂O = 246 g/mol

Mass = 12.6 mol × 246 g/mol

Mass = 3100 g

"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"