Concentration units molality molarity mole fraction and percent - One Line Questions
1.
Percent by mass is defined as: —
(Mass of solute / Mass of solution) * 100
2.
Percent by volume is defined as: —
(Volume of solute / Volume of solution) * 100
3.
What is the mole fraction of solute in a 1 molal aqueous solution of NaCl (molar mass of NaCl = 58.5 g/mol)? —
0.0172
4.
If a solution contains 1 mole of NaCl and 9 moles of water, what is the mole fraction of NaCl? —
5.
A solution contains 0.1 mole of solute and 0.9 moles of solvent. What is the mole fraction of the solvent? —
0.9
6.
If the mole fraction of solute is 0.2, what is the mole fraction of solvent in a binary solution? —
0.8
7.
If 10 g of a solute are dissolved in 100 g of water, and the molar mass of the solute is 50 g/mol, what is the molality of the solution? —
2 m
8.
A solution contains 2 moles of solute in 500 mL of solution. What is its molarity? —
4 M
9.
What is the molality of a solution containing 30 g of methanol (CH3OH, molar mass = 32 g/mol) in 200 g of water? —
0.9375 m
10.
If 58.5 g of NaCl (molar mass = 58.5 g/mol) is dissolved in 500 g of water, what is the molality of the solution? —
1.0 m
11.
If the molality of a solution is 0.5 m, it means: —
0.5 moles of solute are dissolved in 1 kg of solvent.
12.
If the mole fraction of solvent in a binary solution is 0.7, what is the mole fraction of solute? —
0.3
13.
Consider a solution where the mole fraction of water is 0.8 and the mole fraction of ethanol is 0.2. What is the total mole fraction of the solution? —
1.0
14.
What is the mole fraction of solute if the mole fraction of solvent is 0.8 in a binary solution? —
0.2
15.
A solution has a molality of 3 m. If the solvent is water, what is the mass of water in kilograms when 3 moles of solute are dissolved? —
1 kg
16.
If 1 mole of solute is dissolved in 1 kg of solvent, what is the molality of the solution? —
1 m
17.
If a solution has a molarity of 1 M and its density is 1 g/mL, what is its molality (assuming molar mass of solute is negligible compared to solvent)? —
Slightly more than 1 m
18.
A solution is prepared by dissolving 2 moles of solute in 2 liters of solution. What is the molarity? —
1 M
19.
What is the concentration of a solution prepared by dissolving 1 mole of solute in 1000 g of solvent in terms of molality? —
1 m
20.
If the density of a 1 M solution of NaCl is 1.05 g/mL, what is its molality (molar mass of NaCl = 58.5 g/mol)? —
1.02 m
21.
A solution is 5% (w/w) NaOH. If the molar mass of NaOH is 40 g/mol, what is the molality of the solution (assuming the solvent is water)? —
1.39 m
22.
A solution is prepared by mixing 1 mole of solute A and 2 moles of solvent B. What is the mole fraction of solute A? —
1/3
23.
If 18 g of water (molar mass = 18 g/mol) is mixed with 46 g of ethanol (molar mass = 46 g/mol), what is the mole fraction of water? —
1/2
24.
A solution is 10% (w/v) glucose. This means: —
10 g of glucose in 100 mL of solution.
25.
A 10% (w/w) solution of glucose in water means: —
10 g of glucose in 90 g of water.
26.
A solution is prepared by dissolving 10 g of NaOH in 90 g of water. What is the percent by mass of NaOH? —
10%
27.
A solution is prepared by dissolving 50 g of NaOH in enough water to make 100 mL of solution. What is the molarity of the solution (molar mass of NaOH = 40 g/mol)? —
12.5 M
28.
If 20 mL of ethanol is dissolved in 80 mL of water, what is the percent by volume of ethanol? —
20%
29.
What is the percent by volume of a solution prepared by mixing 50 mL of acetic acid with 150 mL of water? —
25%
30.
What is the mass of solute needed to prepare 250 mL of a 0.5 M solution of H2SO4 (molar mass = 98 g/mol)? —
24.5 g
31.
A solution is 5% (v/v) formaldehyde. This means: —
5 mL of formaldehyde in 100 mL of solution.
32.
What is the molarity of a 2 m solution of NaCl in water if the density of the solution is 1.1 g/mL and the molar mass of NaCl is 58.5 g/mol? —
Approximately 1.9 M
33.
How does molarity change with an increase in temperature? —
It decreases
34.
What is the relationship between molarity (M), molality (m), density of solution (d in g/mL), and molar mass of solute (M_solute)? —
M = (1000 * m * d) / (1000 + m * M_solute)
35.
If the molarity of a dilute aqueous solution is M, its molality (m) is approximately: —
m = M
36.
Which concentration unit is most useful for relating to the equilibrium constant (K) in gas-phase reactions? —
Molarity
37.
Which concentration unit is derived from the definition of molar mass and is sensitive to volume changes with temperature? —
Molarity
38.
Which concentration unit is defined as moles of solute per unit volume of solution? —
Molarity
39.
Which concentration unit is independent of temperature? —
Molality
40.
Which of the following concentration units is most suitable for describing the concentration of a gas in a liquid, especially when Henry's Law is applied? —
Mole fraction
41.
Which concentration unit is preferred when dealing with reactions that involve mass changes or are carried out at different temperatures? —
Molality
42.
Which concentration unit is expressed as parts per million (ppm)? —
Percent by mass
43.
Which concentration unit is always dimensionless? —
Mole fraction
44.
The concentration unit that expresses the number of moles of a component per total number of moles in the mixture is called: —
Mole fraction
45.
What is mole fraction (X) defined as? —
Moles of solute / Total moles in solution
46.
What is molarity (M) defined as? —
Moles of solute per liter of solution
47.
What is molality (m) defined as? —
Moles of solute per kilogram of solvent
48.
For very dilute solutions, molarity and molality are approximately equal because: —
The density of the solution is close to 1 g/mL.
49.
A solution has a molarity of 2 M. This means: —
There are 2 moles of solute in 1 liter of solution.
50.
For a binary solution, what is the relationship between the mole fraction of solute (X_A) and the mole fraction of solvent (X_B)? —
X_A + X_B = 1