Chemistry Review for 1st Semester Exam

Transcription

1 Chemistry Review for 1st Semester Exam I. Measurement and Calculations: 1. Demonstrate understanding of the use of measurements in science. You should be able to apply the rules of significant figures to choose answer with the correct number of significant figures. Express the answer in the correct number of significant figures. Label with appropriate units. a g = cm 3 b cm 2 x 1.2 cm = cm c m x 61.5 m = d cm = in You should also be able to measure the length of an object or volume of a liquid to the appropriate number of significant figures based upon the measuring instrument. 2. Which of the following best expresses the width of the business card? a. 5 cm b. 5.0 cm c cm d cm Demonstrate proficiency in the use of scientific notation and use of dimensional analysis (factor label) in metric conversions. Know the meaning of the following metric prefixes and be able to make conversions utilizing them.: milli-, centi-, kilo- Example: 1m 150mm 1000mm 0.15m 3. Complete the indicated conversions: a. 37 g x = mg c. 138 m x = km b. 4.7 kg x = g d mm x = m Modeling Chemistry 1 1st Sem Review-v2.2

2 4. Be able to convert standard notation to scientific notation and vice versa. standard scientific x x Determine the density of an object from a data table or from a graph of mass vs volume. Volume (cm 3 ) Mass (g) Plot the data above and determine the density of the substance. 7. What volume would 150g of the substance occupy? Show work; use labels. 8. Correctly state the law of conservation of mass. 9. If 41g of salt are dissolved in 202g of water what will be the resulting mass? II. Gases and Kinetic Theory 1. Use arrows to identify the relationship between P and T, V and T, P and n and P and V. 2. Identify the law associated with each of the above variables. You should be able to identify the correct graphic representation of the relationships between volume, temperature, and pressure. 3. Which graph describes the relationship between gas pressure and volume? Modeling Chemistry 2 1st Sem Review-v2.2

3 4. Which graph (previous page) describes the relationship between gas pressure and temperature? 5. What temperature scale is used when working with gases? Solve problems given volume, pressure, or temperature of gases. 6. A sample of carbon dioxide has a volume of 2.0 L at a temperature of 10 C. What volume will this sample have when the temperature is increased to 110 C. Assume that the pressure does not change and that no carbon dioxide leaks from the sample. (Use the grid!) 7. A 12.7 L sample of gas is under a pressure of 740 mm Hg at 20 C. What will be the volume of the gas if the pressure increases to 1.00 atm and the temperature drops to 0.0 C? 8. What is the pressure in the bulb for a and b III. The role of energy in physical change 1. Describe the ways energy is stored in solids, liquids and gases. Thermal energy energy of motion related to the absolute temperature Hotter molecules move more rapidly than slower ones; for a given volume the gas will have a greater pressure due to the greater number of Phase energy energy due to attractions between molecules; the stronger the attractions, the lower the energy of the system of particles Lowest for solids, greater in liquids, greatest in gas phase Heat is the transfer of energy into or out of a system due to molecular collisions. Energy is transferred from hotter (faster) molecules to colder (slower) molecules. 2. Explain why the alcohol level in a thermometer rises when it is placed in a warmer fluid. (3-step process) Modeling Chemistry 3 1st Sem Review-v2.2

4 3. Describe what happens (at the molecular level) when a glass of cold water warms up to room temperature. Draw energy bar graphs to account for energy storage and transfer in all sorts of changes. (review ws 1 and 2, quiz in unit 3). 4. A tray of water at 22 C is put in the freezer and cools to -8.0 C When energy is transferred to a sample of matter, either the particles speed up (temperature increases) or they get pulled apart (phase change), but not both at the same time. This helps account for the shape of the warming curve you got in the Icy Hot lab. 5. On the graph above label which phases are present in each portion of the curve. 6. Label the sections in which the thermal energy (E th ) of the sample is changing. 7. Label the sections where the interaction energy (E i ) is changing. Use the equations Q mh, where H f 334 J g, H v 2260 J g to determine the energy transferred to or from water during a phase change. Use Q mc t and c 4.18 J gþc to determine the energy transferred to or from water during heating or cooling. 8. What is the energy required to heat 100. g of coffee from 25 C to 91. C. (Show work) 9. How much energy is released when 75.0 g of water cools from 30 C and ends up completely frozen at 0 C. (Show work) Modeling Chemistry 4 1st Sem Review-v2.2

5 IV. Mixtures and Compounds Describe how matter is organized. 1. You should be able to identify diagrams and distinguish between atoms, molecules, compounds, mixtures, gases, and solids. a. What is represented in Figure A? b. Does Figure B represent a compound or an element? Explain. c. Which diagrams show only molecules? What is different about the molecules represented by the diagrams? 2. Mixtures can be separated by means and compounds can be separated by means. 3. State Avogadro s hypothesis. 4. If two equal volumes of gas A and B are combined (same temp and pressure), how many volumes of product will be formed. Assume A and B are monatomic and draw the above reaction. 5. Draw the reaction above is gas A and B are diatomic. 6. List the 7 diatomic molecules. 7. State the Law of Constant Composition and the Law of Multiple Proportions V. The mole concept and chemical reactions Recognize that atoms are too small to count directly. We determine how many there are in a sample by finding their mass. We use the mole to determine the number of atoms and molecules. Molar mass (on Periodic Table) is relative mass, based originally on hydrogen (lightest element). 1. Calculate the molar mass of the compounds below: Pb(NO3)2 BaSO4 Determine the number of atoms or moles using Avogadro s number and the molar mass of a compound. 2. Solve the following using molar mass, Avogadro s number or both: a. 12 g MgCl2 x = moles MgCl2 Modeling Chemistry 5 1st Sem Review-v2.2

6 b. 3 moles NaCl x = atoms Cl c. 12.0g of PbSO4 x = molecules PbSO4 Determine the empirical and molecular formulas from data. 3. A compound is composed of 7.20 g of carbon, 1.20 g of hydrogen, and 9.60 g of oxygen. The molar mass of the compound is 180 g. Find the empirical and molecular formulas for this compound. Be able to distinguish between the meaning of coefficients and subscripts in a balanced chemical equation. 4. Draw pictures to represent the balanced equation: Ba + 2HCl --> BaCl2 + H2 VI. Matter and Atomic Theory 1. How does Thomson s model of the atom differ from Dalton s. Distinguish between insulators and conductors: 2. Give an example of an insulator and a conductor. 3. Draw a picture of an insulator exposed to a positively charged object 4. Draw a picture of a conductor exposed to a negatively charged object. 5. Define polarization Distinguish between molecular and ionic solids. Molecular solids (formed from atoms of non-metals) exist as separate molecules that attract one another. When dissolved in water, the solution does NOT conduct electricity; e.g., C 6 H 12 O 6. Ionic solids (formed from metal and non-metals) exist as a lattice of charged particles (ions). The formula represents the simplest integer ratio (empirical formula) of the ions; e.g. CaCl 2. When dissolved in water, the solution conducts electricity. Modeling Chemistry 6 1st Sem Review-v2.2

7 Demonstrate knowledge of the meaning of a chemical formula in terms of atoms and molecules. 6. Given the formula of a compound, identify the number of atoms present. a. Pb(NO3)2 b. Na 3 PO 4 c. Al2(SO4)3 7. Name ionic and molecular compounds from formulas and vice versa. Write the formula of binary compounds (formed from two kinds of atoms). a potassium iodide b. nitrogen dioxide c. sodium oxide d. aluminum chloride d. tin(iv) chloride f. iron(iii) sulfide g. phosphorus tribromide 8. Write the name of binary compounds (formed from two kinds of atoms). a. SnO b. SnBr 4 c. SO 2 d. Al 2 O 3 e. NCl 3 f. CaO 9. Write the formula or name of compounds formed from polyatomic ions. a. calcium nitrate b. potassium phosphate c. aluminum acetate d. ammonium sulfate e. Al(OH) 3 f. Cu 2 SO 4 g. (NH4) 2 CO 3 Modeling Chemistry 7 1st Sem Review-v2.2