JOHN BURKE HIGH SCHOOL

Size: px

Start display at page:

Download "JOHN BURKE HIGH SCHOOL"

Teresa Cobb
5 years ago
Views:

JOHN BURKE HIGH SCHOOL Chemistry 2202 Midterm Examination January, 2013 Instructions: Part I: Multiple Choice: Choose the best answer to each item. Place all answers on the Answer Sheet provided.

1 JOHN BURKE HIGH SCHOOL Chemistry 2202 Midterm Examination January, 2013 Instructions: Part I: Multiple Choice: Choose the best answer to each item. Place all answers on the Answer Sheet provided. 40 marks Part II: Constructed Response: Answer all questions as instructed. Place all answers on loose leaf. 40 marks: 38 marks for correct workings 2 marks for the correct usage of significant figures. Name:

2 Part I 1. What is the isotope notation for an element that has 7 protons and 8 neutrons? A. nitrogen - 14 B. nitrogen - 15 C. oxygen - 15 D. oxygen What name is given to atoms of an element that have the same number of protons, but different numbers of neutrons? A. atomic mass units B. avogadro s particles C. isotopes D. isotopic abundances 3. What is the average atomic mass of the imaginary element, Newfoundlandium ( Nl)? Isotope Average Atomic Mass (amu) % Abundance A amu B amu C amu D amu 4. Which term represents the mass of one mole of an element? A. molar mass B. molar volume C. percent composition D. percent volume A sample of an element contains 3.01 x 10 atoms and has mass of g. What is the identity of the element? A. Ba B. Ca C. Cs D. Fe 6. What is the molar mass of (NH 4) 2CO 3? A g/mol B g/mol C g/mol D g/mol 7. Buckminsterfullerines are large molecules that resemble a see-through soccer ball. These molecules are composed entirely of carbon atoms. What is the chemical formula for a buckminsterfullerene that has a molar mass of 841 g/mol? A. C 60 B. C 70 C. C 829 D. C Which calculation requires the use of Avogadro's number? A. mole to atoms B. mole to concentration C. mole to mass D. mole to volume

3 9. What is the mass of mol of CaSO 4 (molar mass = g/mol)? A x 10 g B g C g D x 10 g 10. How many moles are found in 39.2 g of SiO 2? A moles B moles C moles D moles 11. What volume does 3.58 mol of methane gas, CH 4 (g), occupy at STP? A L B L C L D L 12. Which of the following states that Equal volumes of all ideal gases at the same temperature and pressure contain the same number of molecules? A. Amedeo s Law B. Avogadro s Hypothesis C. Law of Definite Proportions D. Law of Combining Volumes 13. Which statement about real gases is true? A. Their molar volumes vary slightly. B. Their particles are not attracted to each other. C. Their particles do not take up space. D. They are hypothetical, in nature. 14. Which statement best represents a qualitative analysis? A. A lab technician measures the amount of sugar in a patient s urine. B. A mechanic tests for the presence of water in a car s gas line. C. A student tests the ph of a local lake, finding it to be 5.6. D. A water analyst finds bottled water to contain traces of impurities. 15. A compound has a mass of 75.0 g. The sample contains 50.0 g of Zn and 25.0 g of S. What is the percentage composition of Zn? A % B % C % D % 16. Which is an empirical formula? A. C H B. CH C. C H D. C H What is the percent composition by mass of sulfur in gypsum, CaSO 4 2 H2O? (Molar Mass of CaSO 2 H O = g/mol) A % B % C % D % 4 2

4 18. When determining the empirical formula of a compound from its percentage composition, why do you base your calculations on a 100 g sample? 23 A. A 100 g sample has exactly particles. This lets you use Avogadro s Constant to determine the percentage composition. B. A 100 g sample allows you to easily convert the percentage of each element in the compound to a mass. C. A 100 g sample allows you to use molar mass to represent the mass of each element in the compound. D. A 100 g sample allows you to use the percentage composition of the compound to determine the multiplier. 19. How many moles of oxygen, O 2 (g), are required to react with mol of ammonia, NH 3 (g)? A mol B mol C mol D mol 4 NH 3 (g) + 7 O 2 (g) 6 H2O (g) + 4 NO 2 (g) 20. Which type of stoichiometry describes the prediction of the mass of one substance produced based on the mass of reactants in a chemical reaction? A. gas B. gravimetric C. solution D. volumetric 21. What is defined as the force exerted on an object per unit of surface area? A. isotopic abundance B. molar volume C. pressure D. STP 22. What is the molecular formula of a species with an empirical formula of CH2O, and a molar mass of g/mol? A. CH2O B. CHO C. C6H12O6 D. C H O Ionic compounds that have water molecules incorporated into their crystal structure are called: A. bucky balls B. crystal lattices C. hydrocarbons D. ionic hydrates 24. A g sample of MgSO 3 xh2o contains: 49.1 g of MgSO 3 ( M = g/mol ) 50.9 g of xh2o ( M = g/mol ) What is the value for x? A. 2 B. 4 C. 6 D A mole ratio shows: A. the limiting and excess reactants B. the number of moles per gram of chemical species C. the ratio between any two species in a balanced chemical equation D. the theoretical yield in a filtration

5 26. Given the balanced chemical equation: 8 F 2 + S 8 8 SF2 What mole ratio would be used to convert a given number of moles of sulfur to moles of SF 2? A. 8 mol SF B. 8 mol S 8 mol F 1 mol F C. 1 mol S D. 8 mol SF 8 mol SF 1 mol S Consider this balanced chemical equation: TiCl 4(s) + O 2 (g) TiO 2 (s) + 2 Cl 2 (g) n = 5.00 mol m =? M = g/mol M = g/mol What mass of TiO 2 (s) is produced when 5.00 mol of TiCl 4 (s) react? A g B g C. 399 g D. 949 g 28. A candle completely burns in air until there is no wax left. Which term best describes the wax? A. actual yield B. excess reactant C. limiting reactant D. theoretical yield 29. After combining solutions of sodium carbonate and calcium nitrate, a student filtered the reaction mixture to collect a precipitate of calcium carbonate. Which occurs if the precipitate is weighed before it is completely dry? A. % yield is higher than it should be B. % yield is lower than it should be C. theoretical yield is higher than it should be D. theoretical yield is lower than it should be 30. Refer to the following reaction: HBrO 3 (aq) + 5 HBr (aq) 3 Br 2 (l) + 3 H2 O (l) n = 6.50 mol n = 1.00 mol Which species is the limiting reactant? A. HBrO 3 B. HBr C. Br 2 D. H O If 2.55 g of silver is expected to be produced and the following data is collected, what is the percent yield? Mass of Filter Paper + Silver 3.28 g Mass of Filter Paper 1.26 g A % B % C % D. 126 % 32. Which is the most concentrated solution? A mol/l B mol/l C mol/l D mol/l

6 33. Which has high solubility in water? A. AgBr B. AgNO 3 C. Ag2S D. Ag SO What volume of aqueous ammonium hydrogen phosphate was produced? A. 0.5 L B. 1.1 L C. 4.5 L D. 6.5 L 2 NH 3 (aq) + H3PO 4 (aq) (NH 4) 2HPO 4 (aq) v = 1.5 L c = 1.20 mol/l c = 1.80 mol/l v =? 35. What mass of H2O(g) is produced from the reaction of 25.0 L of O 2(g) at STP? 4 NH 3(g) + 5 O 2(g) 4 NO(g) + 6 H2O(g) v = 25.0 L m =? A g B g C g D. 121 g V = 22.4 L/mol M = g/mol STP 36. Which of the following will dissociate in water to form a strongly electrolytic solution? A. NaCl B. CO 2 C. methane gas D. sugar solution 37. What is the meaning of the term 'aqueous' when referring to a chemical substance? A. it is in the liquid phase B. it is dissolved in water C. it is not very soluble in water D. it is highly acidic 38. What is the molar concentration of a 2.50 L solution prepared using 0.64 mol CaCl 2? A mol/l B mol/l C mol/l D. 1.6 mol/l 39. What is the correct dissociation equation for magnesium phosphite, Mg 3(PO 3) 2? A. Mg (PO ) (s) Mg (aq) + PO (aq) B. Mg (PO ) (s) 3Mg (aq) + P (aq) + 3O (aq) C. Mg (PO ) (s) Mg (aq) + PO (aq) D. Mg (PO ) (s) 3Mg (aq) + 2 PO (aq) A solution of potassium borate, K3BO 3 (aq), has a potassium ion concentration of 0.750mol/L. What is the concentration of the borate ion? A mol/l B mol/l C mol/l D mol/l

7 Part II {2} 1. Naturally occurring magnesium exists as a mixture of three isotopes. The average atomic mass of naturally occurring magnesium is amu. Mg-24 has an atomic mass of amu and a relative abundance of %. Mg-25 has an atomic mass of amu and a relative abundance of 10.13%. Calculate the atomic mass of the remaining isotope. {3} 2. (a) Aspirin has a percent composition of 60.00% carbon, 4.485% hydrogen, and 35.52% oxygen. Determine the empirical formula for Aspirin. TM {2} (b) If the molar mass of Aspirin is g/mol, what is it s molecular formula? {2} 3. Calculate the number of CO 2 (g) molecules present in a 36.4 L sample at STP. {3} 4. An unknown alkaline earth metal (Group IIA) M reacts with a solution of sodium fluoride, NaF (aq), in a single replacement reaction. When g of the metal M reacts, g of Na (s) precipitates. What is the identity of the metal M? M (s) + 2 NaF (aq) 2 Na (s) + MF 2 (aq) m = g m = g M = g/mol {3} 5. Calculate the mass of silver, Ag (s), expected when Zinc, Zn (s), is placed in ml of a mol/l silver nitrate solution, AgNO (aq). Zn (s) + 2 AgNO 3 (aq) 2 Ag (s) + Zn(NO 3) 2 (aq) 3 {3} 6. Mg(OH) 2 (aq) reacts with HNO 3 (aq) to undergo a neutralization reaction as shown below: Mg(OH) 2 (aq) + 2 HNO 3 (aq) Mg(NO 3) 2 (aq) + 2 HOH (l) What concentration of L Mg(OH) 2 (aq) was required to completely react with 1.50 L of mol/l HNO (aq)? 3 {2} 7. Calculate the mass of potassium dichromate, K2Cr2O 7 (s), required to prepare ml of a mol/l solution. ( Molar mass of K Cr O = g/mol ) By calculation, determine the limiting reagent in the reaction below. 2 AgNO 3 (aq) + CaCl 2 (aq) 2 AgCl (s) + Ca(NO 3) 2 (aq) m = 75.0 g m = 75.0 g M = g/mol M = g/mol {3} (a) Determine the limiting reactant. {2} (b) What mass of precipitate should be produced? {2} (c) The student actually recovers 57.5 g of precipitate in the lab. What is the percent yield? {2} (d) Should the lab be repeated? Why or why not? {2} (e) List 2 possible sources of error for this experiment. {2} 9. (a) Write a dissociation equation to show what happens when, calcium chloride, Na3PO 4 (s) is dissolved in water. {5} (b) The solution in (a) above was formed by dissolving 3.50 g of Na3PO 4 (s) in sufficient water to produce a 2.00 L solution. Calculate the concentration of Na PO (aq) and the concentration of the ions present. 3 4 Thought of the day: An eye for an eye only ends up making the whole world blind. Mahatma Gandhi

CHEMISTRY 2202 FINAL EXAMINATION Value: 100% General Instructions

Name: Teacher: DO NOT OPEN THE EXAMINATION PAPER UNTIL YOU ARE TOLD BY THE SUPERVISOR TO BEGIN CHEMISTRY 2202 FINAL EXAMINATION Value: 100% General Instructions This examination consists of two parts.