Some Basic Concepts of Chemistry

Topics in this chapter

• Mole Concept and Molar Mass
• Laws of Chemical Combination
• Composition and Chemical Formulae
• Stoichiometric Calculations
• Limiting Reagents
• Solution Concentration and Mixing
• Gas Laws and Molar Volume
• Significant Figures and Measurements

Cheat sheet

Practice questions

1. Question 1Q-1EA8F3

   What is the total number of significant figures in the number 0.0025?

   1. A.2
   2. B.4
   3. C.5
   4. D.6
   See the answer and solution
2. Question 2Q-B83D04

   Calculate the mass percentage of carbon in ethanol ($C_2H_5OH$). (Atomic masses: $C = 12 \text{ g mol}^{-1}$, $H = 1 \text{ g mol}^{-1}$, $O = 16 \text{ g mol}^{-1}$)

   1. A.52.17%
   2. B.34.78%
   3. C.26.08%
   4. D.61.02%
   See the answer and solution
3. Question 3Q-467B93

   What is the concentration of a solution in molality ($m$) if $4 \text{ g}$ of NaOH is dissolved in $500 \text{ g}$ of water? (Molar mass of $NaOH = 40 \text{ g mol}^{-1}$)

   1. A.$0.1 \text{ m}$
   2. B.$0.2 \text{ m}$
   3. C.$0.4 \text{ m}$
   4. D.$0.08 \text{ m}$
   See the answer and solution
4. Question 4Q-048A2D

   An organic compound contains $40\%$ Carbon, $6.67\%$ Hydrogen, and $53.33\%$ Oxygen by mass. What is its empirical formula?

   1. A.$CH_2O$
   2. B.$C_2H_4O_2$
   3. C.$CHO$
   4. D.$CH_3O$
   See the answer and solution
5. Question 5Q-2AF815

   Calculate the volume occupied by $14 \text{ g}$ of nitrogen gas ($N_2$) at STP.

   1. A.$11.2 \text{ L}$
   2. B.$22.4 \text{ L}$
   3. C.$5.6 \text{ L}$
   4. D.$44.8 \text{ L}$
   See the answer and solution