Which substance has a molar mass of 142 g?

a. mgcl2
b. p2o5
c. bacl2
d. alcl3

B) P₂O₅

Explanation:

A) MgCl₂

Molar mass of Mg = 24

Molar mass of Cl = 35.5

Molar mass = 24 + 2×35.5 = 95 g/mol

B) P₂O₅

Molar mass of P = 31

Molar mass of  O = 16

Molar mass = 31 ×2 + 5×16 = 142 g/mol

C) BaCl₂

Molar mass of Ba = 137.33

Molar mass of  Cl = 35.5

Molar mass = 137.33 + 2×35.5 = 208.33 g/mol

D) AlCl₃

Molar mass of  Al = 27

Molar mass of  Cl = 35.5

Molar mass =  27 + 3×35.5 = 133.5

"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"

the product of the pressure and volume is also constant