IB chemistry Units 1-3 review Quantitative chemistry Significant figures The mole- be able to convert to number of particles and mass Finding empirical and molecular formulas from mass percentage States of matter (know how potential and kinetic energy change in a change of state) Chemical equations (reactants products) Balance chemical equations Stoichiometry- be able to covert moles in a chemical reaction Limiting reactants Theoretical yield and percent yield Gases- be able to use the molar volume of a gas (22.4 dm 3 per mole at STP) Gas laws Ideal gas law: PV=nRT Solutions: solute, solvent, concentration, and titrations Atomic structure Subatomic particles- know their location and charge Atomic number Mass number Nuclear symbol Nucleus Ions- cations, anions Isotopes The mass spectrometer Finding relative atomic mass using percentages Electromagnetic spectrum- wavelengths, frequency, energy Line emission spectrums Ground state Excited states Electron configuration Remember the exceptions (Cu and Cr) Finding valence electrons (group 1 has 1, group 2 has 2, group 13 has 3, group 14 has 4, group 15 has 5, etc) Periodicity The periodic table Effective nuclear charge Atomic radius Ionic radius Ionization energy Electronegativity Melting points Reactivity of metals increases as you go down a group Reactivity of nonmetals- increases as you go up a group Metals in water form metal hydroxides (OH) and hydrogen Metal oxides in water from metal hydroxides Nonmetal oxides in water form acids (H in front of the nonmetal)
Practice Questions Multiple choice (paper 1) 1. The simplest formula for a hydrocarbon that is 20.0 percent hydrogen by mass is a. CH b. CH 2 c. CH 3 d. C 2 H 2 e. C 2 H 5 2. 3 Cu + 8 HNO 3 3Cu(NO 3 ) 2 + 2NO + 4H 2 O Copper reacts with dilute nitric acid according to the following reaction. If 2 moles of copper metal are allowed to react with excess nitric acid, how many grams of NO gas can be formed? a. 90.0 g b. 80.0 g c. 40.0 g d. 20.0 g e. 1.5 g 3. Which pair of atoms represents nuclei that have the same number of neutrons? a. 56 Co and 58 Co b. 57 Mn and 57 Fe c. 58 Ni and 57 Fe d. 58 Ni and 57 Co e. 59 Ni and 56 Fe 4. How many valence electrons does arsenic have? a. 3 b. 4 c. 5 d. 6 e. 7 5. Which element has the largest atomic radius? a. B b. Al c. Ga d. In e. Tl 6. Which of the following properties generally decreases across the periodic table from sodium to chlorine a. First ionization energy b. Atomic mass c. Electronegativity d. Atomic radius 7. The effective nuclear charge experienced by the outermost electron of Na is different than the effective nuclear charge experienced by the outermost electron of Ne. This difference best accounts for which of the following? a. Na has a greater density than Ne. b. Na has lower first ionization energy than Ne. c. Na has a higher melting point than Ne. d. Na has a higher neutron-to-proton ratio than Ne. e. Na has fewer naturally occurring isotopes than Ne. 8. The first ionization energy for magnesium is 730 kj/mol. The third ionization energy for magnesium is 7700 kj/mol. What is the most likely value for magnesium s second ionization energy? a.490 kj/mol b. 1400 kj/mol c. 4200 kj/mol d. 7100 kj/mol e. 8400 kj/mol 9. Which of the following statements is true regarding sodium and chlorine? a. sodium has greater electronegativity and larger first ionization energy b. chlorine has a larger atomic radius and a larger first ionization energy c. chlorine has greater electronegativity and a larger atomic radius d. chlorine has greater electronegativity and a larger first ionization energy e. sodium has larger first ionization energy and a larger atomic radius
10. Identify the element with a 1+ charge and 10 electrons? a. Na b. Mg c. F d. Ne 11. How many significant figures should the result of the following calculation have? (0.04500)(2.002)(38.26 1.2) a. 1 b. 2 c. 3 d. 4 e. 5 12. 100.0 cm 3 of a 0.50 mol dm -3 solution of BaCl 2 is added to a 50.0 cm 3 of a 0.10 mol dm -3 solution of Na 2 SO 4. A precipitate of BaSO 4 is formed according to the equation below. BaCl 2 (aq) + Na 2 SO 4 (aq) BaSO 4 (s) + 2NaCl(aq) What is the amount, in mol, of BaSO 4 produced? a. 0.0050 b. 0.010 c. 0.050 d. 0.10 13. Which species have the same electron configuration? I. O 2-, F -, Ne II. Li +, Na +, K + III. S 2-, Ar, K + a. I and II only b. I and III only c. II and III only d. I, II, and III 14. For which element are the group number and period number the same? a. Li b. Be c. B d. Mg 15. Which of the reactions below occur as written? i. Br 2 + 2I - 2 Br - + I 2 ii. Br 2 + 2Cl - 2 Br - + Cl 2 a. i only b. ii only c. both i and ii d. neither i or ii 16. What amount of oxygen, O 2, (in moles) contains 1.8 x 10 22 molecules? a. 0.0030 b. 0.030 c. 0.30 d. 3.0 17. The diagram represent the emission spectrum of hydrogen. Groups of arrows are labelled W, X, and Y Which statement is correct? a. The arrow represent the transition of electrons to different energy levels when heat is supplied b. The arrows W represent emission in the UV region c. The smallest arrow of X represents a violet line in the emission spectrum d. The arrows Y represent emission of electromagnetic waves with higher energy than those represented by X and W
18. The horizontal axis of the bar chart represents the elements of period 3 from sodium to chlorine (excluding Si). What could be the vertical axis represent? a. Melting point of the element b. Electronegativity of the bonded atom c. Ionic radius of the most common ion d. First ionization energy in the gaseous state 19. How many electrons does 31 P 3- contain? a. 12 b. 15 c. 16 d. 18 20. When the following reaction is balanced, what is the coefficient for iron? Fe + O 2 Fe 2 O 3 a. 2 b. 3 c. 4 d. 5 21. 15.00 g of magnesium oxide, MgO, when heated, produced 1.02 g of magnesium, Mg. Which is the correct expression for the percentage yield of magnesium? 2MgO 2Mg + O 2 a. 15.00 x 2 x 100 / 1.02 b. 15.00 x 40.3 x 100 x 1.02/ 40.3 c. 1.02 x 40.3 / ( 15.00 x 24.3) d. 1.00 x 40.3 x 100 / (15.00 x 24.3) 22. Four identical containers under the same conditions are filled with gases as shown below. Which container and contents have the highest mass? B 23. Wave A has a wavelength = 1.2 x 10 2 m and wave B has a wavelength = 1.4 x 10-2 m. Which wave has the most energy? a. Wave A b. wave B c. they have the same amount d. unable to determine
Free response (paper 2) 1. Answer the following questions about the element selenium, Se (atomic number 34) a. Samples of natural selenium contain six stable isotopes. In terms of atomic structure, explain what these isotopes have in common, and how they differ. Same number of protons but different number of neutrons b. In terms of atomic structure, explain why the first ionization energy of selenium is i. Less than that of bromine (atomic number 35) and The ionized electron in both Se and Br are in the same energy level but Br has more protons than Se so the attraction to the nucleus is greater ii. Greater than that of tellurium (atomic number 52). The electron removed from Te is in the 5 th energy level while the electron removed from Se is in the 4 th energy level. It requires more energy because it is closer to the nucleus (higher effective nuclear charge) 2. Explain why the atomic radius of Li is larger than that of Be. Li and Be have the same energy levels but Li has less protons so they feel a smaller effective nuclear charge therefore it is bigger 3. Write the electron configuration for Cu and Cu 2+ Cu: [Ar]4s 1 3d 10 Cu 2+ : [Ar] 3d 9 4. a. Describe the process occurring at stage Q and stage S Q: ionization S: deflection by magnetic field b. Define the term relative atomic mass. Average mass of all isotopes taking into account the abundance c. Calculate, showing your working, the relative atomic mass of magnesium, giving your answer to two decimal places 24.32 5. A. State the number of protons, electrons, and neutrons in the ion 15 7N 3- P: 7 e: 10 n: 8 6. State and explain the trends in the atomic radius and the ionization energy a. For the alkali metals Li to Cs Radius increases: as you go down the group, there more energy levels are added to the atom Ionization energy decreases: bigger atoms don t hold on to their electrons as well so it is easier to remove b. For period 3 elements Na to Cl Radius decreases: same number of energy levels but more protons to pull electrons in tighter Ionization energy increases: smaller atoms hold onto their electrons better to they are harder to remove
7. Write an equation for each reaction between water and a. Sodium oxide Na 2 O + H 2 O 2NaOH b. Sulfur dioxide SO 2 + H 2 O H 2 SO 3 8. When a small quantity of strongly smelling gas such as ammonia is released into the air, it can be detected several meters away in a short time. a. Use the kinetic molecular theory to explain why this happens. Gas molecules move very quickly and spread through the air b. State and explain how the time taken to detect the gas changes when the temperature is increased Less time, increased temperatures increases the speed of the molecules and they spread out more quickly. 9. 27. 82 g of hydrated sodium carbonate crystals, Na 2 CO 3 xh 2 O, was dissolved in water and made up to 1.000 dm 3. 25.00 cm 3 of this solution was neutralized by 48.80 cm 3 of hydrochloric acid of concentration 0.100 mol dm -3. Na 2 CO 3 + 2HCl 2NaCl + H 2 O + CO 2 a. Calculate the molar concentration of the sodium carbonate neutralized by the hydrochloric acid 0.096 mol dm -3 b. Determine the mass of sodium carbonate neutralized by acid and hence the mass of sodium carbonate present in 1.000 dm 3 of solution. 10.36 g c. Calculate the mass of water in the hydrated crystals and hence find the value of x. 17.46 g of water so x = 10 10. Airbags are an important safety features in vehicles. Sodium azide, potassium nitrate, and silicon dioxide have been used in one design of airbag. Two students looked at data in a simulated computer-based experiment to determine the volume of nitrogen generated in an airbag. Sodium azide, a toxic compound, undergoes the following decomposition reaction under certain conditions. 2NaN 3 (S) 2Na(s) + 3N 2 (g) Using the simulation program, the students entered the following data into the computer. Temperature ( ᴼC) Mass of NaN 3 (s) (kg) Pressure (atm) 25.00 0.0650 1.08 a. State the number of significant figures for the temperature, mass, and pressure data. Temp: 4 mass: 3 pressure: 3 b. Calculate the amount, in mol, of sodium azide present 0.00100 mol c. Determine the volume of nitrogen gas, in dm3, produced under these conditions based on this reaction. 0.0340 dm 3