Question

1) When a mole fraction of a solute is one, based on the definition there is?

a) 1.0 g of solute per 100g of solution

b) is a 1:1 ratio of solute to solvent

c) only solute present

d) 1.0 mole of solute and 99 moles of solvent

e) only solvent present

2) Curious George put on goggles, went into the lab and measured out 25.0 mL of 3.00 M hydrochloric acid and added it to a beaker containing 100.0 mL of water. What is the final concentration of the dilution? (show your work)

a) 3.00 M b) 0.750 M c) 12.0 M d) 0.600 M e) 0.300 M

Answer 1

1). Given that, mole fraction of solute = 1

We know that,

Mole fraction = Moles of solute / (Moles of solute + Moles of solvent)

Moles of solute / (Moles of solute + Moles of solvent) = 1

Moles of solute = Moles of solute + Moles of solvent

Moles of solvent = 0

This means that only solute is present.

So correct option is:

c) only solute present

2). Initial volume, V1 = 25.0 mL

Initial molarity, M1 = 3.00 M

Final volume = 100 + 25 = 125 mL

Final molarity = M2

We have:

M1V1 = M2V2

25.0 * 3.0 = 125 * M2

M2 = 25.0 * 3.0 /125

= 0.6 M

Hence, final concentration = d). 0.600 M