What are the units and numerical values of standard temperature? Solution 1) Thi

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1) This is a pretty straightforward density question using the formula, density = mass / volume First calculate the volume of the room by multiplying the length times width times height. volume = 3m x 3.4m x 3.7m = 37.74 meters cubed since the density is given in grams per cubic cm, convert the volume into cubic centimeters by multiplying by 1,000,000 37.74 meters cubed = 37,740,000 cubic cm now just plug in density and volume to get the mass 0.00125 g / cubic cm = mass / 37740000 cubic cm mass = 47175 grams to get this value in kg, just divide by 1000 the final answer is 47.175 kg (47 kg in proper sig figs) 2) This is a two step problem. First find the volume of nitrogen by calculating 80% of 18L. 18L x 0.8 = 14.4 L To determine the mass, you must first calculate the number of moles using the formula PV = nRT, remember to convert temperature into Kelvin. (1.2atm)(14.4L) = n(.0821 atmL/molesK)(298K) 17.28 = 24.4658n n = 1.415844907 moles To convert this value into grams, simply multiply by the molar mass of nitrogen gas, which is 28 g/mol because nitrogen gas is N2. 1.415844907mol x 28g/mol = 30.64365741g (31g in proper sig figs) 3) This question is fairly simple. First calculate the molar mass of KMnO4 by adding the molar masses of the elements that make it up. K = 39 g/mol Mn = 55 g/mol O = 16 g/mol KMnO4 = 39 + 55 + 4(16) = 158 g/mol To determine the number of moles in a 22 gram sample, just divide 22 by 158. 22g / (158g/mol) = 0.1392405063 mol (0.14 mol in proper sig figs) 4) This is a fairly simple equation question. First balance the equation. C2H6 + O2 -> CO2 + H2O 2 C2H6 + 7 O2 -> 4 CO2 + 6 H2O If there are 4.66 mol of ethane, you can use the mole ratios to determine the amounts of the other three substances. Oxygen: 2/7 = 4.66/x x = 16.31 mol (16.3 mol in proper sig figs) CO2: 2/4 = 4.66/x x = 9.32 mol (already in proper sig figs) H2O: 2/6 = 4.66/x x = 13.98 mol (14.0 mol in proper sig figs) 5) This is a two part question. First calculate the number of moles of H3PO4 by dividing 8.81g by the molar mass. Molar Mass of H3PO4 = 3(1) + 31 + 4(16) = 98 g/mol 8.81g / (98 g/mol) = 0.0898979592 mol Since there is a 1:1 mole ratio between H3PO4 and Na3PO4, 0.0898979592 moles of H3PO4 will produce 0.0898979592 moles of Na3PO4. To convert this value into moles of Na3PO4 multiply by the molar mass. Molar mass of Na3PO4 = 3(23) + 31 + 4(16) = 164 g/mol 0.0898979592 mol x 164 g/mol = 14.74326531g (14.7g in proper sig figs) 6) This is a fairly simple question. First recognize the oxidation and reduction that are going on the in the reaction. 3 moles of X are being oxidized to become 3 moles of X 2+ 2 moles of Y 3+ are being reduced to become 2 moles of Y Based on the reduction potentials, determine the cell potential. Since 3 moles of X are being oxidized, negate the reduction potential and multiply by 3. 2.495 V x 3 = 7.485 V Since 2 moles of Y 3+ are being reduced, multiply the reduction potential by 2. 2.573 x 2 = 5.146 V Adding these values gives you the cell potential. 5.146 V + 7.485 V = 12.631 V

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