Answer:
The molality is unchanged (0.96 molal)
Explanation:
<u>Step 1: </u>Data given
mass of glucose = 4.35 grams
volume of water = 25.0 mL
Density of water = 1.00 g/mL
Molar mass of glucose = 180.156 g/mol
<u>Step 2:</u> Calculate number of moles
moles of glucose = mass of glucose / Molar mass of glucose
moles of glucose = 4.35 grams / 180.156 g/mol
moles of glucose = 0.024 moles
<u>Step 3:</u> Calculate mass of water
mass = density * volume
mass of water = 1.00 g/mL * 25.0 mL
mass of water = 25 g = 0.025 kg
<u>Step 4</u>: Calculate molality
molality = Number of moles / mass of water
molality = 0.024 moles / 0.025 kg
molality = <u>0.96 molal</u>
Suppose you take a solution and add more solvent, so that the original mass of solvent is doubled.
This means double mass of water = 2*0.025 kg = 0.050 kg
Now molality is 0.024 moles / 0.050 kg = 0.48 molal
When the mass of solvent is doubled, the molality is halved from 0.96 molal to <u>0.48 molal</u>
You take this newsolution and add more solute, so that the original mass of the solute is doubled.
This means double mass of glucose = 2*4.35 g = 8.70 g
8.70 grams of glucose = 8.7 grams * 180.156 g/mol = 0.048 moles
molality = 0.048 moles / 0.050 kg = <u>0.96 molal</u>
The molality is unchanged
