Answer:
no. of water molecules associated to each molecule of [tex]MnCl_2[/tex] = 4
Explanation:
Mass of [tex]MnCl_2[/tex] before heating = 19.8 g
Mass of [tex]MnCl_2[/tex] after heating = 12.6 g
Difference in mass of [tex]MnCl_2[/tex] before and after heating
= 19.8 - 12.6 = 7.2 g
Difference in mass corresponds to mass of water driven out.
Molar mass of water = 18 g/mol
No. of moles of water = [tex]\frac{7.2}{18} = 0.4\ mol[/tex]
Mass of [tex]MnCl_2[/tex] obtained after heating is mass of anhydrous [tex]MnCl_2[/tex].
Mass of anhydrous [tex]MnCl_2[/tex] = 12.6 g
Molar mass of [tex]MnCl_2[/tex] = 125.9 g/mol
No. of mol of anhydrous [tex]MnCl_2[/tex] = [tex]\frac{125.9}{125.9} = 0.1\ mol[/tex]
so,
0.1 mol of [tex]MnCl_2[/tex] have 0.4 mol of water
1 mol of [tex]MnCl_2[/tex] will have = [tex]\frac{0.4}{0.1} =4\ mol[/tex]
Hence, no. of water molecules associated to each molecule of [tex]MnCl_2[/tex] = 4
