Question

question 2 (1 point)
after heating until a constant mass was established, the sample, evaporating dish
and watch glass had a mass of 44.7640 g. what is the mass of water that was driven
off by the heating?
a) 1.6464 g
b) 18.02 g/mol
c) 44.7640 g
d) 0.4366 g

Explanation:

To solve this, we assume we know the initial mass (before heating) of the sample, evaporating dish, and watch glass. Usually, in such experiments (like hydrate analysis), the initial mass (let's say \( M_{initial} \)) is the mass before heating, and the final mass ( \( M_{final} = 44.7640 \, g \)) is after water is driven off. The mass of water driven off is \( M_{initial} - M_{final} \).

But since this is a multiple - choice question, we analyze the options:

• Option B is a molar mass (units \( g/mol \)), not a mass of water, so eliminate B.
• Option C is the final mass, not the mass of water driven off, eliminate C.
• We need to find the difference. If we assume the initial mass (sample + dish + watch glass + water) was, for example, \( 44.7640 + 1.6464=46.4104 \, g \) (to get option A) or \( 44.7640 + 0.4366 = 45.2006 \, g \) (to get option D). In typical hydrate experiments, the mass of water driven off is calculated as initial mass minus final mass. If we consider common values, and since option B and C are incorrect, and if we assume the initial mass was \( 44.7640+1.6464 = 46.4104 \, g \), then the mass of water is \( 46.4104 - 44.7640=1.6464 \, g \).

Answer:

A) 1.6464 g