Reality Check

Reality Check Since the density of palladium (12.02 g/cm3) is larger than that of the metal bars, it would seem that they are slighdy contaminated by a less dense metal. 

Reality Check Note that although molecular formulas give the composition of the molecule, they reveal nothing about the way the atoms fit together. In that sense they are less useful than structural formulas. 

Reality Check A cation always contains more protons than electrons the reverse is true for an anion. 

Reality Check The atomic mass of Br, 79.90, is just about halfway between the masses of the two isotopes, 78.92 and 80.92. So, it is reasonable that it should contain nearly equal amounts of the two isotopes. 

Reality Check Because every known substance has a molar mass greater than 1 g/mol, the mass of the sample in grams is always larger than the number of moles. 

Reality Check A mole ratio of 1.00 A 1.00 B 333 C would imply a formula A3B3C10 if the mole ratio were 1.00 A 2.50 B 5.50 C, the formula would be A2B5Cn. In general, multiply through by the smallest whole number that will give integers for all the subscripts. 

Reality Check The molarity decreases when water is added. The moles of solute stay the same, but the volume of the solution increases. 

Reality Check The concentration of K+ should be twice that of Cr2072 in either solution. It is ... 

Reality Check In part (c), note that the amount of water added to the solid H2X is irrelevant to the solution of the problem. 

Reality Check It s a good idea to check mass and charge balance in the final equation. In part (b), for example,... 

Reality Check The volume of the tank is never used in any of the calculations for the different parts of the problem. The mass of the propane is relevant only in part (c). 

Reality Check Notice that the average speed is very high. In miles per hour it is... 

Reality Check Because it takes longer for gas X to effuse, it must have a larger molar mass than argon. It does ... 

Reality Check Compare this value with that listed in Table 6.1 for the second line in the Balmer series. 

Reality Check To construct an orbital diagram, start with the electron configuration and apply Hund s rule. 

Reality Check Check these answers against Figure 6.13 and 6.15. 

Reality Check Whenever you write a Lewis structure, check to see if it follows the octet rule. The structures written for OCl and C2H6 do just that each atom except H is surrounded by eight electrons. 

Reality Check NH4+ is like CH4, GeF2 like SO and PF3 like NH3. 

Reality Check If you are asked to predict the hybridization, as you are here, the geometry as in Example 7.6, or the polarity as in Example 7.7, you have to start with Lewis structures that is why they are so important... 

Reality Check There are two pi bonds in a triple bond, one in a double bond, and none in a single bond. 

Reality Check The negative sign indicates that heat flows from the water to its surroundings as it cools. 

Reality Check Notice that qieacu0n is negative, so the solution process is exothermic. That is reasonable since the temperature of the water increases. 

Reality Check Notice that thermochemical equations can be added in exactly the same manner as algebraic equations in this case 1C02 and 02 canceled when the equations were added. 

Reality Check Notice that the reaction is exothermic, but only slightly so. If you carry out the reaction in the laboratory, you find that the solution temperature increases slightly. 

Reality Check Note that in this case AH and AE differ from one another by only about 0.1%, a very small difference indeed. 

Reality Check The calculations in (b) show that about 770 grams are required for saturation (100% relative humidity). To get 33% relative humidity, you would expect to need about a third of that amount, which is what the calculations in (c) do give. 

Reality Check This value is reasonable in the sense that lowering the temperature should reduce the vapor pressure. 

Reality Check In acetic acid, the H atom bonded to oxygen in one molecule forms a hydrogen bond with an oxygen in an adjacent molecule. The same situation applies in hydrazine if you substitute nitrogen for oxygen. 

Reality Check In FCC unit cells, the fraction of empty space is 0.26. When this is factored into the above, the calculated density of silver becomes 14.3 — (0.26)(14.3) =... 

Reality Check You expect the vapor pressure lowering to be small (0.589 mm Hg)... 

Reality Check Actually, the freezing point is somewhat lower, about — 37°C (—35°F), which reminds us that the equation used, ATf = kftn, is a limiting law, strictly valid only in very dilute solution. 

Reality Check This is a quite reasonable answer as shown earlier, a 0.10 Af solution at 25°C has an osmotic pressure of 2.4 atm. 

Reality Check You would get the same result (m = 2) if you used any two points. Try it ... 

Reality Check In (b), reducing the amount present to 15% takes more time than two half-lives (i.e., more than the time to reduce to 25%). The answer is larger than 2(6.60 X 103), as it should be. In (c), the rate is dependent on the initial concentration, unlike the half-life in (a)—which is independent of the initial amount... 

Reality Check Notice that the concentration drops from 1.00 M to 0.50 M in 2 h. If the reaction were zero-order, it would be all over after four hours. If it were first-order, the concentration would be 0.25 M after four hours. 

Reality Check Notice that the concentration of 02, a product in the reaction, appears in the denominator. The rate is inversely proportional to the concentration of molecular oxygen, a feature that you would never have predicted from the balanced equation for the reaction. As the concentration of 02 builds up, the rate slows down. 

Reality Check Note that the equilibrium partial pressure of HI is intermediate between its value before equilibrium was established (0.80 atm) and that immediately afterward (1.00 atm). This is exactly what Le Chatelier s principle predicts part of the added HI is consumed to re-establish equilibrium. 

Reality Check Aspirin is a relatively strong weak acid it would be located near the top of Table 13.2. 

Reality Check When equal amounts of a weak acid and its conjugate base are present, the pH of the buffer is equal to pK. ... 

Reality Check Notice that in both (a) and (b), the change in pH is quite small, less than 0.1 unit... 

Reality Check Notice that moving from left to right, one en replaces two OH- ions. This makes sense an en molecule has two lone pairs that can bond to the metal OH-has only one. 

Reality Check To check the answer in (a), use the calculated concentration to determine Kgpi... 

Reality Check The solubility in 0.10 M Na2S04 is much less than that in pure water (1.1 X 10 9< 1.0 X 10-5), which is exactly what we predicted. 

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