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Unformatted text preview: roberts (eer474) Sample Exam Two Shear (52375) 1 This print-out should have 34 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Which one of the following formulas is wrong? 1. sodium nitrate : NaNO 3 2. sodium sulfate : Na 2 SO 4 3. ammonium perchlorate : NH 4 ClO 3 cor- rect 4. potassium chloride : KCl 5. calcium sulfate : CaSO 4 Explanation: The ammonium ion is NH + 4 ; the perchlor ate ion is derived from perchlor ic acid (HClO 4 ) and has the formula ClO 4 . One ClO 4 is needed to balance the charge on each NH + 4 , so the formula for ammonium perchlorate is NH 4 ClO 4 . The sodium ion is Na + ; the sulfate ion is SO 2 4 . Two Na + are needed to balance the charge on each SO 2 4 , so the formula for sodium sulfate is Na 2 SO 4 . The sodium ion is Na + ; the nitrate ion is NO 3 . One NO 3 is needed to balance the charge on each Na + , so the formula for sodium nitrate is NaNO 3 . The potassium ion is K + ; the chloride ion is Cl . One K + is needed to balance the charge on each Cl , so the formula for potassium chloride is KCl. The calcium ion is Ca 2+ ; the sulfate ion is SO 2 4 . One Ca 2+ is needed to balance the charge on each SO 2 4 , so the formula for calcium sulfate is CaSO 4 . 002 10.0 points Give the formula for sodium nitrate. 1. Na(NO 3 ) 2 2. Na 3 NO 3 3. NaNO 3 correct 4. Na(NO) 3 Explanation: The sodium ion is Na + ; the nitrate ion is NO 3 . One Na + is needed to balance the charge of each NO 3 , so the formula is NaNO 3 . 003 10.0 points Calcium metal reacts with water to form cal- cium hydroxide and hydrogen gas. How much hydrogen is formed when 0.50 g of calcium are added to water? 1. 0.10 g 2. 0.025 g correct 3. 0.50 g 4. 0.050 g Explanation: m Ca = 0 . 50 g The balanced equation is Ca + 2 H 2 O Ca(OH) 2 + H 2 , and indicates the 1 mol H 2 is produced for each mole Ca reacted. First we calculate moles Ca present: ? mol Ca = 0 . 50 g Ca 1 mol Ca 40 . 1 g Ca = 0 . 0125 mol Ca Since 1 mol H 2 is produced for each mole Ca reacted, 0.0125 mol H 2 would be produced from 0.0125 mol Ca. The molar mass of H 2 is used to convert to grams H 2 : ? g H 2 = 0 . 0125 mol H 2 2 g H 2 1 mol H 2 = 0 . 025 g H 2 004 10.0 points Fluorine is more electronegative than oxygen because 1. the effective nuclear charge of oxygen is greater than that of fluorine. roberts (eer474) Sample Exam Two Shear (52375) 2 2. the outer orbitals of oxygen are located closer to the nucleus than the outer orbitals of fluorine. 3. False; oxygen is more electronegative than fluorine. 4. the effective nuclear charge of fluorine is greater than that of oxygen. correct 5. the outer orbitals of fluorine are located further from the nucleus than the outer or- bitals of oxygen....
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- Spring '08