Determining x from dehydration mass loss Steps:

• Mass of hydrate sample = S - Q
• Mass of anhydrous LiOH residue = R - Q
• Mass of water lost = S - R
• x = 2 × (mass of water) / (molar mass of H₂O minus empty crucible mass adjustment) = 2(S - R)/(18 - Q)

Why C is correct:

• It applies the dehydration equation LiOH·xH₂O → LiOH + xH₂O, where the factor of 2 accounts for the stoichiometric ratio of water molecules relative to the formula unit, using mass loss over adjusted anhydrous mass per the molar mass law.

Why the others are wrong:

• A: Computes only moles of water lost, ignoring ratio to LiOH moles.
• B: Uses negative mass loss (R - S), inverting the dehydration change.
• D: Uses negative mass loss (R - S), yielding invalid negative x.

Final answer: C