Krypton crystallizes with a face-centered cubic unit cell of edge 559 pm.?
a) There are 14 atoms ( 8 at the corners and 6 at the face centers) assigned to a fcc unit cell. Since the atoms at the corners are shared between eight adjacent unit cells cells and the atoms at the face centers are shared you have net 4 atoms per unit cell. To calculate the density divide the mass of the atoms per cell by the cell volume: ρ = 4∙m / a³ = 4 ∙ 83.798 amu / (559pm)³ = 4 ∙ 83.798 ∙ 1.66054×10⁻²⁷kg / (559×10⁻¹²m)³ = 3376.58kg/m³ b) Consider the diagonal of a face of the cell. Since the atoms are in direct contact in the hemispherical plane, the length of the diagonal equals quadruple radius of the atom. From basic geometry you know that the length of diagonal in square of side length a is √2∙a Hence: √2∙a = 4∙r => r = a / ( 2∙√2) = 559pm / (2∙√2) = 197.6pm c) Assuming the atom is a rigid sphere of radius r: V_atom = (4/3)∙π∙r³ = π∙a³ / (12∙√2) = π∙(559×10⁻¹²m)³ / (12∙√2) = 3.234×10⁻²⁹m³ d) f = (V_cell - 4∙V_atom) / V_cell = 1 - 4∙V_atom/V_cell = 1 - 4∙ (π∙a³ / (12∙√2)) / a³ = 1 - π/(3∙√2)) = 0.26 = 26%
What is the theoretical and percent yield in SO3 based on the reaction? atm, g, mmHg. trying to figure out this problem and having no luck?
Consider the following reaction: 2SO2(g)+O2(g)→2SO3(g) If 275.9mL of SO2 is allowed to react with 167.6mL of O2 (both measured at 325K and 49.6mmHg ), what is the limiting reactant? --> SO2 What is the theoretical yield of SO3? If 191.0mL of SO3 is collected (measured at 325K and 49.6mmHg ), what is the percent yield for the reaction?
Why is the United States so religious?
There are regional cultural differences in the United States. The Northwest (Washington and Oregon) does not have a very high rate of religious affiliation or practice. However, the Southeast (Mississippi, Alabama, Georgia, etc.) does.In the Southeast, church membership plays an important socializing function; people label themselves according to which church they attend. I also think that having faith in (typically the Protestant interpretation of) God is associated with Southern pride. Other things that Southerners tend to identify with culturally are the Southern accent, football, Southern foods, and the idea of minors using “ma’am” and “sir” when talking to adults.African-Americans are a significant minority group in the Southeast. In the African-American community, pastors are seen as indispensable male authority figures. Churches are important social, political, and even artistic centers. Martin Luther King, Jr. was a preacher. Whitney Houston and Stevie Wonder sang in church when they were young.Additionally, I think that the following came into play:In the 1950s, politicians convinced the public that a good way to fight against Communist influences was by promoting religion in public life. President Eisenhower signed a bill that inserted the phrase “under God” into the Pledge of Allegiance.In the late 1960s, scores of young people liberated themselves from the tropes of 1950s life. Some experimented with drugs. Some tried religion. The religious experimentation was geared toward finding something different than the mainline experiences they had growing up. This could mean Eastern religions or contemporary Evangelical flavors of Christianity.In the late 1970s, religious activists coalesced politically, encouraging like-minded people to vote. They played a key role in electing Ronald Reagan in 1980. Collectively, these people came to be known as the “Religious Right.”
For each of the following reactions, balance the chemical equation, calculate the emf, and calculate G° at 298
The easiest way for you to solve this kind of problems is to look into the Table of The Standard Reduction Potentials, find corresponding half reactions, and combine the half reactions together. Let me show you one case and you should solve the rest. OK? (c) I got the following from Chemistry The Central Science, by Brown, Lemay and Bursten. I do not have your book, do not I? Cu2+ + e− → Cu+, E° = 0.153V . . . . . . . . . . . . . (1) NO3- + 4H+ + 3e- → NO + 2H2O, E° = 0.96V . . (2) (2) - 3x(1) to cancel all e-: 3Cu+ + NO3- + 4H+ → 3Cu2+ + NO + 2H2O, E° = 0.81V
Rocket physics question?
Calculate the height when the fuel runs out: s = ut + 0.5*a*t^2 s = 0 + 0.5*30*30^2 s = 13500 m Calculate the velocity when the fuel runs out: v = u + at v = 0 + 30*30 v = 900 m/s Calculate maximum height: v^2 = u^2 + 2as 0 = 900^2 - 2*9.81*s 19.62s = 810000 s = 41284 m Max height = 41284 + 13500 = 55 km to two significant figures. Now to calculate flight time after the rocket burn: s = vt - 0.5at^2 -13500 = 900t - 0.5*9.81*t^2 4.905t^2 - 900t - 13500 = 0 109t^2 - 20000t - 300000 = 0 Solve using the quadratic formula: t = ( -b +- sqrt(b^2 - 4ac) ) / (2a) t = ( 20000 +- sqrt(20000^2 + 4*109*300000) ) / (2*109) t = (20000 +- 530,800,000) / 218 t = (20000 + 23039.1) / 218 t = (20000 - 23039.1) / 218 t = 43,039.1 / 218 t = -3,039.1 / 218 t = 197.4 t = -13.94 Well the time is clearly not negative, so it must be 197.4 seconds. Added to the 30s rocket burn, we get a total flight time of 227.4 seconds, or 230 seconds to two significant figures.
The freezing point of t-butanol is 25.50°C and Kf is 9.1°C·kg/mol. Usually t-butanol absorbs water on exposure
The freezing point of a solution is always lower than the freezing point of the pure solvent. This is because solute molecules interfere with the crystallization process. There is an equation that relates the change in freezing temperature to the concentration of the solution. It looks like this: ΔTf = Kf x m x i where ΔTf is the change in freezing temperature, Kf is the freezing point depression constant, m is the molality of the solution (moles of solute per kilogram of solvent) and i is the van't Hoff factor. The van't Hoff factor is important if the solute is an electrolyte, but since water isn't, i = 1. There's no need to include i in this equation. Now then, the freezing point of the t-butanol drops from 25.50ºC to 24.59ºC when it absorbs a certain amount of water. That's a change of 0.91ºC. If you plug that and the other given values into the equation, you get: ΔTf = Kf x m 0.91ºC = (9.1 ºC*kg/mol) x m m = 0.10 mol/kg So there is one-tenth of a mole of water present for every kilogram of solvent. The amount of solute initially present was 10.9 g, or 0.0109 kg. 0.10 m = (mol) / (0.0109 kg) (mol) = 1.1e-3 mol Now we simply convert moles of water to grams of water, using the molar mass of water, which is 18.02 g/mol. 1.1e-3 mol x (18.02 g)/(1 mol) = 2.0e-2 g H2O. So there you have it...the t-butanol must have absorbed approximately two centigrams of water. I hope that helps. Good luck!
Consider the following reaction: 2SO2(g) + O2(g) -> 2SO3(g)?
2 SO2(g) + O2(g) → 2 SO3(g) At constant pressure and temperature, volume of a gas is proportional to the number of moles of a gas. We can use a simple proportion and equation coefficients to calculate the number of milliliters of oxygen needed to react with 176.9 mL of sulfur dioxide: (2 mol SO2) : (1 mol O2) = (276.8 mL SO2) : (X mL O2) X = [(1 mol O2)(276.8 mL SO2)] / (2 mol SO2) X = 138.4 mL O2 needed Answer: Since as much as 163.5 mL of oxygen is available, oxygen is present in excess. The limiting reactant is sulfur dioxide. Next, we can calculate the theoretical yield of sulfur trioxide using a similar same simple proportion: (2 mol SO2) : (2 mol SO3) = (276.8 mL SO2) : (X mL SO3) X = [(2 mol SO3)(276.8 mL SO2)] / (2 mol SO2) X = 276.8 mL SO3 Answer: The theoretical yield of SO3 is 276.8 mL. % yield = [(actual yield)(100%0] / (theoretical yield) % yield = [(176.9 mL)(100%0] / (276.8 mL) % yield = 63.91% Answer: The percent yield for the reaction is 63.91%
Which scientists were imprisoned or killed for their discoveries?
Hippasus.He is a student of the famous mathematician lived in Ancient Greece named, Pythagoras.Doesn’t ring a bell?Don’t worry.He is the first European who discovered the relationship among the three sides in a right triangle.a^2+b^2=c^2Hippasus however noticed something weird.Back then rational numbers were found out. Rational number means the number can be expressed by p/q, (q doesn’t equal 0 and p and q are both integers).Hippasus noticed that the square root of some integers, such as 2 and 3, cannot be expressed in such a way. We later found out they are actually irrational numbers.For example, square root of 4 is 2 but square root of 2 cannot be expressed by p/q.So he asked his teacher Pythagoras why would that be.Pythagoras couldn’t answer this question.so……Pythagoras tied him up and threw Hippasus into the sea.