Questions asked by learningchemistry

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• How does the loss or gain of an electron affect the atomic radius?
  
• When a molecule has an #sp^3d# hybridization with 2 lone pairs, the molecular geometry is T-shaped. Why is the T-shape preferable over a trigonal planar shape? (ie, why are the lone pairs positioned that way?)
  
• Compare and contrast the **first** ionization energies of K and Ca? Compare and contrast the **second** ionization energies of K and Ca?
  
• If x is an integer less than 1000 that has a remainder of 1 when it is divided by 2, 3, 4, 5, 6, or 7, what is one possible value of x?
  
• How many grams of potassium chlorate are required in the preparation of 90.0 cubic decimeters of oxygen?
  
• If Strontium-74 is unstable what type of decay does it undergo? What type of radioactive decay would Hydrogen-3 undergo and why?
  
• What determines the state of matter of a substance?
  
• How did the First and Second Sino-Japanese War contribute to a century of Chinese humiliation?
  
• The valve cap n a bicycle wheel is 12.5 in from the center of the wheel. From the position shown, the wheel starts to roll. After the wheel has turned 390°, how far above the ground is the valve cap? Assume that the outer radius of the tire is 13.375 in.
  
• #CrO_4^(2-)# is added to a solution where the original concentration of #Sr^(2+)# is #1.0 * 10^-3#. Assuming the concentration of #Sr^(2+)# stays constant, will a precipitate of #SrCrO_4# (Ksp = #3.6 * 10^-5#) form when #[CrO_4^(2-)]# = #3.0 * 10^-5# M?
  
• Chemistry question about solubility products and #K_(sp)#?
  
• The solubility products of #Fe(OH)_2# and #Fe(OH)_3# are #10^(-17)# and #10^(-38)# respectively. If the concentrations of #Fe^(2+)# and #Fe^(3+)# are each #10^(-5)#, what is the #[OH^-]# when each just begin to precipitate?
  
• Prove that #sec^4s - tan^2s# equals to #tan^4s + sec^2s#? Thanks in advance
  
• Find #x# in degrees radians (either one is fine)? #tanxsinx-tanx=0# Thanks in advance
  
• Solve for #x# in #sin2xsinx-cos2xcosx=-cosx#?
  
• Given that #sinθ = 0.6820# and that #θ# is in quadrant III, find #sin2θ# and the quadrant in which #2θ# lies?
  
• Simplify #(sintheta + cos2theta - 1)/(costheta-sin2theta)#?
  
• #cos(pi/24) = ?# #A. # #sin((11pi)/24)# #B. # #sin((23pi)/24)# #C. # #sec((23pi)/24)# #D. # #sec((11pi)/24)#
  
• The straight line #y = mx# where #m > 0# forms an angle of #30^@# with the positive #x#-axis. What does #m# equal?
  
• Prove that #(sint-cost)/(sint+cost) = (2sin^2t-1)/(1+2sintcost)#?
  
• How to prove #cos^2(theta/2) = (1+sectheta)/(2sectheta)#? Thanks in advance
  
• Prove/verify the identities: #tan(x+(3pi)/4) = (tanx-1)/(1+tanx)#?
  
• Prove/verify the identities: #(cos(-t))/(sec(-t)+tan(-t)) = 1 + sint#?
  
• Find #sintheta#, #costheta#, and #tantheta# under the given conditions: #sin2theta=1/5, pi/2 <= 2theta < pi#?
  
• Prove/verify the identity? #sin(alpha-beta)/(cos(alpha+beta)) = (tanalpha-tanbeta)/(1-tanalphatanbeta)#
  
• What is the pOH of a #0.50 M# solution of acetic acid? The acid dissociation constant of acetic acid at #25.0^@ "C"# is #1.75 xx 10^-5#.
  
• What is the #"pH"# of a #"1.5-M"# solution of ammonia? The dissociation constant of ammonia at #25.0^@"C"# is #1.80 * 10^-5#.
  
• Calculate the #[OH^-]# and the #[H^+]# of a #0.0020# #"M"# solution of #"NaOH"#, a strong base?
  
• Use Law of Cosines: Two airplanes leave an airport at the same time. The first flies 150 km/h in a direction of #320^@#. The second flies 200 km/h in a direction of #200^@#. After 3 hr, how far apart are the planes?
  
• Find all the complex solutions of the equation #x^6 + 64 = 0#?
  
• Solve #3x^2 + (1+2i)x + 1 - i = 0#?
  
• If 40. mL of .10M NaOH is used to titrate 25 mL of acetic acid, how many grams of acetic acid were present?
  
• Find all radian solutions on the interval #(-oo, oo)#? #sin(2x) - tanx = 0#
  
• Two airplanes leave an airport at the same time. The first flies #(210 " km")/("hr")# in a direction of #290^@#. The second flies #(180 " km")/("hr")# in a direction of #185^@#. After 3 hr, how far apart are the planes?
  
• A parallelogram has sides of length #15.4# and #9.8#. Its area is #72.9#. Find the measures of the angles?
  
• Find all the complex solutions of the equation? #x^4 - i = 0#
  
• Convert to a rectangular equation? #r + rsintheta = 1#
  
• Convert to rectangular form? #r^2sin^2theta = -22#
  
• If air is #20.9%# oxygen by volume, 1. How many liters of air at #25.5^@ "C"# and #1.000# atm are needed for the complete combustion of #15.0 "kg"# of propane vapor? 2. What volume of each product is produced?
  
• Solve #lnx = 1-ln(x+2)# for #x#?
  
• The half-life of Tungsten-181 is 121 days. If you start with 3 pounds of it, how much do you have after 7 years?
  
• What does it mean when someone says something like "Question #0a266"? Where are those numbered/lettered questions?
  
• Can reaction that is endothermic with a decrease in entropy occur spontaneously? Why?
  
• #DeltaG = DeltaH - TDeltaS# If #DeltaH = -232 kJ, DeltaS = 138 J/K and T = 273 K,# is this reaction spontaneous? Solve to prove and explain
  
• #CO (s) + S (s) + 2O_2 (g) -> CaSO_4 (s)# #DeltaH_(rxn)^@ = -888.3 " kJ/mol", DeltaS_(rxn)^@ = -118.0 "J/mol K"# At what temperature will this reaction be spontaneous?
  
• Solve for #x# in #log_3(2x-1) < 0#?
  
• The graph of #y = log_("1/a")x# is the same as the graph of? 1. #y = -a^x# 2. #y = log_ax# 3. #y = (1/a)^x# 4. #y = -log_ax# 5. #y = log_a(-x)#
  
• The specific heat capacity of an unknown liquid is #0.32# #"J"/("kgK")#. The density of the liquid is #0.0321# #"g/mL"#. If a chemist applies #243# #"J"# of heat to #300# #"mL"# of this liquid starting at #27.1 ^@# #C#, what is the final temperature?
  
• The standard enthalpy of formation for sulfur dioxide gas is #"-296.8 kJ/mol"#. Calculate the amount of energy given off in #"kJ"# when #"30.0 g"# of #"SO"_2 "(g)"# is formed from its elements?
  
• Statistics question?
  
• Statistics question?
  
• In a survey of men in the United States (ages 20-29), the mean height was 69.6 inches with a standard deviation of 3.0 inches. If 320 men are randomly selected, about how many of them are taller than 71 inches?
  
• If #sectheta = a# and #sintheta < 0#, find the exact valaues of #sintheta#?
  
• #sin(alpha/2) = 1/4# and #405^@ < alpha/2 < 450^@#. Find #cosalpha#"?
  
• Suppose that the population of a colony of bacteria increases exponentially. If the population at the start is 300 and 4 hours later it is 1800, how long (from the start) will it take for the population to reach 3000?
  
• Solve the equation #ix^3 + 1 - isqrt3 = 0#. Express your answer in trigonometric form?
  
• What is the molality of a 15.0 M solution of phosphoric acid with a density of 1.65 g/mL?
  
• Which of the following liquids will have the lowest freezing point?
  
• Kaplan SAT Prep Plus Math Question?