Chemistry Midterm Review Topics: Unit 1: laboratory equipment and safety rules accuracy vs precision scientific method: observation, hypothesis. experimental design: independent vs dependent variables, control group, constants theory vs law Unit 2 classification of matter (pure substances elements & compounds vs mixtures homo/heterogeneous) mole, molar mass, molar conversions (grams <- -> moles <--> molecules) percent composition Unit 3 chemical vs physical changes endo vs exothermic factors affecting rate of reaction (temp, surface area, concentration, catalyst) Unit 4 kinetic molecular theory and ideal gases Temperature and pressure conversions Reading manometers Name significant figures scientific notation density percent error unit conversions (dimensional analysis) empirical vs molecular formula solutions molarity calculations dilutions calculations physical vs chemical properties separation of mixtures techniques writing and balancing equations stoichiometry (mole to mole ratios based on balanced equations) gas laws: Dalton, Graham, Boyle, Charles, Gay- Lussac, Combined, Avogadro, Ideal Gas stoichiometry Unit 1 Lab Equipment Unit 5 Properties of solids and liquids Polarity Heat calculations Intermolecular forces & their relationship with viscosity, volatility, vapor pressure, boiling point, surface tension Unit 6 Atomic Theory and History Atomic Structure (protons, neutrons, electrons, isotopes, ions) Nuclear Stability Nuclear Decay Equations Half Life Phases of matter graphs: heating curve, phase diagram, vapor pressure curve, solubility curve Colligative properties (freezing point depression, boiling point elevation) What is the volume of liquid in the graduated cylinders below? Express your answer using the proper number of significant figures. This packet contains practice questions, but is not meant to serve as a comprehensive review. Please also reference your old tests/quizzes for more practice problems!
Scientific Method, Experimental Design MOUTHWASH: The makers of brand A mouthwash want to prove that their mouthwash kills more bacteria than the other 4 leading brands of mouthwash. They organize 60 test subjects into 6 groups of 10 test subjects. The data for the experiment is shown to the right. 1. Identify the independent variable 2. Identity the dependent variable: 3. List any constants in this experiment 4. What was the control group? 5. What should the conclusion be? 6. How can the makers of brand A mouthwash now test the rinse time (time mouthwash was in mouth) vs how much bacteria is found in the mouth? Mouthwash used time mouthwash was in mouth none 135 A 60 sec. 23 B 60 sec. 170 C 60 sec. 84 D 60 sec. 39 E 60 sec. 81 # of bacteria in mouth (average) Scientific Notation Significant Figures Metric Conversions Sig Figs and Calculations
Density 1. Calculate the density of an object whose mass is 1.6g and volume is 0.234 ml. Report your answer using the proper number of significant figures! Mole, Molar Conversions 2. A cube has a mass of 3.56g with a length of 33.3cm, width of 10.9cm, and a height of 0.22cm. Calculate the density. Report your answer using the proper number of significant figures! Percent Error Unit 2 Classification of Matter Percent Composition Separation Techniques Image of separation technique Name of technique Physical properties taken advantage of
Empirical and Molecular Formulas Dilutions Molarity Physical vs Chemical Properties and Changes
Unit 3 Unit 4 Phase Changes 1. Drawing a particle diagram for a sample in the: (i) solid phase (labeled A), (ii) liquid phase (labeled B), and (iii) gas phase (labeled C). 2. Labeling each arrow (D, E, F, G, H, I) with the appropriate phase change (ex. fusion/melting). 3. Indicate which phase changes are endothermic and which are exothermic. Dalton s Law 1. A mixture of H2, NH3, CO2 and N2 has a total pressure of 800. Torr. The partial pressures of 3 gases are given. What is the partial pressure of N2? PH2=114 torr PNH3=171 torr PCO2=229 torr 2. A 250. ml sample of oxygen is collected over water at 25 C and 760.0 torr pressure. What is the pressure of the dry gas alone? (vapor pressure of water at 25 C=23.8 torr) 3. A 54.0 ml sample of oxygen is collected over water at 23 C and 770.0 torr pressure. What is the volume of the dry gas at STP (Vapor pressure of water at 23 C=21.1 torr) Balance and identify the type of chemical reaction Graham s Law 1. Rank the following gases from slowest to fastest rate of diffusion: H2, N2, Ne, 2. Compare the rates of effusion of Xe and Ar at the same temperature and pressure. 3. A sample of hydrogen gas effuses through a porous container about 9 times faster than an unknown gas. Estimate the molar mass of the unknown gas. Boyle s Law Stoichiometry: Mole-Mole Questions 1. Given the balanced equation representing a reaction: C3H8(g) + 5 O2(g) 3 CO2(g) + 4 H2O(g) What is the total number of moles of O 2(g) required for the complete combustion of 1.5 moles of C 3H 8(g)? 2. Given the equation: H2 (g) + Cl2 (g) 2 HCl (g) What is the total number of moles of HCl (g) produced when 3.27 moles of H2 (g) is completely consumed? 3. Given the balanced equation: 2 Na + S Na2S What is the total number of moles of S that reacted when 4.73 moles of Na were completely consumed?
Charles Law Unit 5 Heat Calculations 1. Gold has a specific heat capacity of 0.129 J/g C. How many joules of heat energy are required to raise the temperature of 15 grams of gold from 22 C to 85 C? 2. How much heat energy is required to melt 25 grams of ice at 0 C? The heat of fusion of H2O is 334 J/g. Ideal Gas Law Heating Curve 1. What is the boiling point of the substance? 2. What is the melting point of the substance? 3. What letter represents the range where the solid is being warmed? 4. What letter represents the range where the liquid is being warmed? 5. What letter represents the range where the gas is being warmed? 6. Which letter(s) represent a change in potential energy? 7. Which letter(s) represent a change in kinetic energy? 8. Which letter represents condensation? 9. Which letter represents freezing? Gas Stoichiometry Vapor Pressure Curve 1. Which of the substances has the lowest boiling point? 2. Which of the substances has the highest boiling point? 3. Which of the substances has the highest vapor pressure at 40 C? 4. Which of the substances has a normal boiling point of 79 C? 5. At what temperature will ethanol boil when the atmospheric pressure is 50 kpa? 6. At what atmospheric pressure will propanone boil at 20 C? 7. At what atmospheric pressure will water boil at 90 C?
Phase Diagram Unit 6 1. Label the following on the graph: Atoms & stability a. Solid Complete the table below and determine if the element is a cation, an anion, or a neutral atom b. Liquid c. Gas 2. What is the temperature and pressure at the triple point? Nuclear Notation Atomic Number Mass Number # Protons # Neutrons # Electrons Cation? Anion? Neutral? Stable or unstable? 3. What is the temperature and pressure at the critical point? 4. What is the normal melting point of this substance? 3 7 3 4 3 neutral unstable 5. What is the normal boiling point of this substance? 30 18 Cation (+1) Solubility Curve 1. Which salt is least soluble in water at 20 C? 35 20 Anion (-2) 2. How many grams of KCl can be dissolved in 100 grams of water at 80 C? 28 31 3. At 40 C, how many grams of KNO3 can be dissolved in 100 grams of water? 39 19 neutral 4. At 30 C, 90 g of NaNO3 is dissolved in 100 grams of water. Is this solution unsaturated, saturated, or super saturated? Nuclear Decay Equations 5. Which solutes show a decrease in solubility as temperature increases? Write balanced nuclear equations for the following a. The alpha decay of Francium-220 b. The beta decay of Strontium-90
Half-Life 1. The half-life of polonium-209 is equal to 102 years. If you take 24 grams of this isotope and bury it in a sealed container, how much polonium-209 would remain in the container after 408 years? 2. The half-life of francium-223 is 22 minutes. In a laboratory, a student is given a container with 6.4 grams of francium-223 at 12:00PM. When the student analyzes the container at 1:50PM, how many grams of francium-223 will remain? 3. The half-life of vanadium-48 is 16 days. On January 1 st, a sample of vanadium-48 was buried in a sealed container. The container is opened on February 18 th, 48 days later, and it is determined that 7.5 grams of vanadium-48 is present in the container. How many grams of vanadium-48 were originally present in the container on January 1 st? 4. The half-life of iron-61 is 6 minutes. In a laboratory, a student is given a container with a sample of iron-61 at 12:00PM. When the student analyzes the container at 12:36PM, it is determined that 0.80 gram of iron-61 is present. How many grams of iron-61 were originally present at 12:00PM?