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Review%20of%20Chem%201211%20material%20Answers

Review%20of%20Chem%201211%20material%20Answers - CHEM 1212...

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CHEM 1212 Review of Chem 1211 material: 1. How many moles are in 21.3 g of O 2 ? 21.3 g * (1 mol / 32 g) = 0.666 mol of O 2 2. Balance the chemical reaction: Al + O 2 Al 2 O 3 What is the mass of O 2 needed to react 72 g of Al? What is the mass of Al 2 O 3 formed? 4 Al + 3 O 2 2 Al 2 O 3 72 g Al * (1 mol Al / 26.98 g) * (3 mol O 2 / 4 mol Al) * (32 g / 1 mol O 2 ) = 64.05 g = 64 g of O 2 3. How much water is added to 12 mL of 1.0 M HCl to obtain a solution that is 0.04 M HCl? Initial number of moles = 0.012 L * 1.0 M = 0.012 moles Final conditions: 0.012 moles of HCl and a Molarity of 0.04 M Volume = moles / M Volume = 0.012 moles / 0.04 M = 0.3 L Final volume is 300 mL; so 288 mL of water must be added to the original 12 mL. 4. After dissolving 73 g of CaCl 2 in 55 L of water, what is the molarity of Cl - ions in solution? CaCl 2 Ca 2+ + 2 Cl - 73 g CaCl 2 * (1 mol CaCl 2 / 110.98 g) * (2 mol Cl - / 1 mol CaCl 2 ) = 1.3156 moles of Cl - Molarity of Cl - ions = 1.3156 moles / 55 L = 0.02392 M = 0.024 M 5. What is the expected shape of CCl 4 ? Is this molecule polar? The expected shape is tetrahedral: The molecules is non -polar, the pull of each Cl cancels each other out 6. Why is water polar?
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