On recrystallization, 20g of magnesium tetraoxosuphate (IV) forms 41 g of magnesium tetraoxosulphate (IV) crystals, MgSO₄. yH₂O. The value of y is?

(Mg = 24, S = 32, O = 16, H = 1)

olyezema

4 years ago

n=m/M
M=24+32+64=120g
n=20/120=0.166g
0.166g=41/M
M=41/0.1666=246g
MgSO4.xH2O=246
120+18x=246
18x=246-120=126
x=126/18=7.

Derek644222

2 years ago

To find the value of

y, we need to calculate the moles of MgSO4 before and after recrystallization where molar mass of MgSO4 is = 24+32+4(16) = 120
and molar mass of MgSO4•yH2O = (120 + y18)
1: Moles of MgSO4 before recrystallization:
n = m/M
= 20/120
= 0.1667mol

2: Moles of MgSO4 after recrystallization:
n = m/M
= 41/( (120 + y18)

Since the substance doesn't change during recrystallization, the moles before and after would be equated as thus:
0.1667= 41/(120 + y18)

now making (120 + y18) the subject of formula we have (120 + y18) = 41/0.1667
= (120 + y18) = 246
:· y18 = 246 – 120
y18 = 126
y = 126/18
y = 7
so the correct option is D

King33Victor

3 months ago

the sentence structure is wrong myschool.
why can't u just say after crystallization, instead of recrystallization. still u can use recrystallization in the other way round. water should have been lost after crystallization

Hermes2005

3 years ago

no such thing as magnesium tetraoxosulphate iv