Recent Homework Questions About Chemistry
According to his prelaboratory theoretical yield calculations, a student's experiment should have produced 1.41 g of magnesium oxide. When he weighed his product after reaction, only 1.33 g of magnesium oxide was present. What is the student's percent yield?
Saturday, December 6, 2014 at 4:44pm
Consider the following data. DeltaHf (Na2O (s))=-414kJ/mol Delta H sublimation(Na)=109 kJ/mol I.E. (Na)=495 kJ/mol Bond Energy (O2) = 495 kJ/mol E.A. (O) = -141 kJ/mol E.A. (O -) = 878 kJ/mol Use this information to calculate the lattice energy of Na2O (s). So, we have the ...
Saturday, December 6, 2014 at 3:47pm
What percent (by mass) of granulated sugar is fructose, and what percent of it is sucrose? Background: We are doing a colligative properties lab in my class where we are to add 20 grams, 40 grams, 60 grams, and 80 grams of sugar to 100 grams of water, and use the change in the...
Saturday, December 6, 2014 at 12:04pm
Acettlene gas (C2H2) is used in welding. During one job, a welder burns 48.0 g of acetylene. Using a balanced equation for the complete combustion of acetylene, calculate the following: Balanced Equation a) the mass of oxygen used b) the mass if carbon dioxide produced c) the ...
Saturday, December 6, 2014 at 11:34am
What is the Van't Hoff Factor of MgSO4*7H2O? We're doing a colligative properties lab at my school where we dissolve various amounts of MgSO4 in 100 grams of water. What value/range of values should I expect the Van't Hoff Factor to be?
Saturday, December 6, 2014 at 10:41am
What mass of solid sodium acetate, NaCH3COO, must be added to 2.50 L of an aqueous solution of 0.55 M acetic acid, CH3COOH, in order to make a buffer solution whose pH is 4.50 ? Assume that adding the solid does not change the volume of the solution. Use the simultaneous ...
Saturday, December 6, 2014 at 5:28am
At 35°C, Kc = 1.6 X 10-5 M for the reaction 2NOCI(g) 2NO(g) + Cl2 (g)' Calculate the concentrations of all species at equilibrium for each of the following systems. Note any simplifying assumptions made in the calculations. 3.0 mol NO(g) and 1.0 mol ofCl2(g) in a 1.0 L...
Saturday, December 6, 2014 at 5:27am
At a total atmospheric pressure of 1.00 atm, the partial pressure of CO2 in air is approximately 4.0×10−4 atm. If at 20 ∘C and a partial pressure of 760 mmHg, the solubility of CO2 in water is 0.169 g/100mL, what is the solubility of CO2 in an open bottle of ...
Friday, December 5, 2014 at 11:09pm
What is the osmolarity of a typical oral rehydration solution (ORS) for infants that contains 95mEq/LNa+ , 25mEq/LK+ , 115mEq/LCl− , and 2.5% glucose? The molecular weight of glucose is 180 amu.
Friday, December 5, 2014 at 11:07pm
Ringer's solution, used in the treatment of burns and wounds, is prepared by dissolving 8.6 g of NaCl, 0.30 g of KCl, and 0.33 g of CaCl2 in water and diluting to a volume of 1.00 L. What is the osmolarity of Ringers solution?
Friday, December 5, 2014 at 11:04pm
The ΔH of the reaction below is -575.13 kJ. Is this reaction spontaneous? 2ZnS + 3O2 + C → 2SO2 + 2Zn + CO2 A. It is not because the ΔH of the reaction is negative. B. It is because the ΔH of the reaction is negative. C. It depends on the temperature ...
Friday, December 5, 2014 at 9:42pm
Oxygen gas may be prepared by decomposing hydrogen peroxide, h2o2, using manganese (IV) oxide catalyst: 2H2O2(liquid) ----> 2H2O(liquid) + O2(gas) Calculate the amount of oxygen that will be produced from 1.35 moles of H2O2 Determine the mass of oxygen gas that can be ...
Friday, December 5, 2014 at 9:40pm
Consider the reaction: 2H2S(g)⇌2H2(g)+S2(g) An equilibrium mixture of this reaction at a certain temperature was found to have [H2S]= 0.542M , [H2]= 2.64×10−2M , and [S2]= 7.54×10−3M . What is the value of the equilibrium constant at this ...
Friday, December 5, 2014 at 6:04pm
An archeological artifact was subjected to radiocarbon dating. The artifact showed a carbon-14 decay rate of 13.8 disintegrations/ min per gram of carbon. Carbon-14 has a half-life of 5715 years, and currently living organisms decay at the rate of 15.3 disintegrations/ min per...
Friday, December 5, 2014 at 4:45pm
The standard potential for the following galvanic cell is 1.72V : Be(s)|Be2+(aq)||Pb2+(aq)|Pb(s) The standard reduction potential for the Pb2+/Pb half-cell: E = -.13V Calculate the standard reduction potential for the Be2+/Be half-cell. What I know: Be is the anode Pb is the ...
Friday, December 5, 2014 at 11:57am
Merchants usually sell small nuts, washers, and bolts by weight (like jelly beans!) rather than by individually counting the items. Suppose a particular type of washer weighs 0.128 g on the average. What would 130. such washers weigh?
Friday, December 5, 2014 at 9:53am
for the reaction A + B C the concentrations of AB, and C are 0.2M, 0.4M and0.)M respectively at 0 minutes. After 30 minutes the concentrations of A and B drop to ).080mM and 0.280M respectively, while the concentration of C rises to 0.120M. Calculate the rate of this reaction.
Friday, December 5, 2014 at 9:17am
The reaction for the complete combustion of acetylene is shown below. C2H2(g) + 5/2 O2(g) -----------> 2 CO2(g) + H2O(l) ÎH = -1299 kJ Use this reaction and the data below to calculate the heat of formation for acetylene. ÎHf[H2O(l)] = -285.8 kJ/mol ...
Friday, December 5, 2014 at 8:09am
In the following reaction, how many liters of carbon dioxide will be produced if 250 liters of oxygen is used in the combustion of sucrose given that both gases are at STP? C12H22O11 + 1202 -> 12CO2 + 11H2O I have had other ones in my homework that were very easy but this ...
Friday, December 5, 2014 at 7:41am
) Indicate how each of the following errors would affect(increase, decrease, or no change) your calculated value for the molar volume of O2 at STP (assuming that you complete the expiriment otherwise correctly). In each case, explain your answer. A. Your sample was not ...
Friday, December 5, 2014 at 2:14am
How do I do the empirical formula for 37.01% carbon, 2.22% hydrogen, 18.50% nitrogen, and 42.27% oxygen? My teacher gave me the answer (C7H5N3O6), but I can never get that answer.
Friday, December 5, 2014 at 1:23am
At temperatures above 0°C, what is the sign of the change in free energy for the conversion of liquid water to ice? A. Positive B. Zero C. Negative D. Not known I don't this it is A. I thought it might be c.
Thursday, December 4, 2014 at 11:37pm
a balloon is filled with 15 L of an ideal gas of 20C. at this temperature the pressure of the gas is 1520 mm Hg. Suppose that the volume of the gas is reduced to 5 L at 290 K. what is the new pressure of the gas in atmospheres?
Thursday, December 4, 2014 at 9:56pm
20 grams magnesium metal react with excess oxygen and 28 grams of magnesium oxide are produced in lab what is percent yield? If 99.8 g of aluminum nitrate are reacted with excess sulfuric acid what would be the theoretical yield in grams of aluminum sulfate? i have done both ...
Thursday, December 4, 2014 at 7:41pm
Given the equation N2(g)+3H2(g)→2NH3(g), what is the total number of moles of NH3 produced when 10 mol of H2 reacts completely with N2? 1. 2.0 mol 2. 3.0 mol 3. 6.7 mol 4. 15 mol
Thursday, December 4, 2014 at 7:36pm
According to the reaction 2Al+3H2SO4→3H2+Al2(SO4)3, the total number of moles of H2SO4 needed to react completely with 5.0 mol of AL is 1. 2.5 mol 2. 5.0 mol 3. 7.5 mol 4. 9.0 mol
Thursday, December 4, 2014 at 7:32pm
A sample of 0.250 g of nickel complex was titrated with 0.150 M EDTA. If the titration of the nickel sample required 7.5 mL of EDTA to reach the equivalence point, what is the percent nickel in the sample?
Thursday, December 4, 2014 at 6:50pm
The Ksp of calcium hydroxide, Ca(OH)2, is 4.68 x 10-6 at 289.15K. Calculate the pH of a saturated solution. Here's my work: 4.68 x 10-6= 4s^3 s= 0.0105 -log(0.0105)= 1.98 14-1.98=12.02 The answer is supposed to be 12.324, but I'm not sure what I'm doing wrong. Is ...
Thursday, December 4, 2014 at 6:32pm
9.0 g of KCl was dissolved in 300 mL of water in a calorimeter. Calculate the heat of solution in kJ/mol if the temperature dropped by 2.53 K on dissolution. The specific heat of water is 4.184 J/g K
Thursday, December 4, 2014 at 10:52am
My chemistry is bad. I know these are very easy but I cannot solve them . 1. a) Prepare 200 ml of 2 M HCl solution from stock bottle containing 37% w/w HCl and d = 1.2 (g/ml). MWHCl = 36.5 g b) Calculate M of 37% w/w HCl solution? d= 1.2, then solve the above problem 2. a) ...
Thursday, December 4, 2014 at 4:13am
what is the mass (by difference) of a sample if the initial mass of the sample in the bottle was 29.89-g and the final mass of the bottle and sample was 22.01-g ?
Thursday, December 4, 2014 at 1:55am
A sample of gas in a cylinder of volume 3.78 L at 318 K and 3.3 atm expands to 6.76 L by two diﬀerent pathways. Path A is an isothermal, reversible expansion. Calculate the work for Path A. Answer in units of J
Wednesday, December 3, 2014 at 11:30pm
Write an equilibrium expression for each chemical equation involving one or more solid or liquid reactants or products. HCHO2(aq)+H2O(l)⇌H3O+(aq)+CHOͨ2;2(aq) Use A for [HCHO2], B for [H2O], C for [H3O+], D for [CHO−2].
Wednesday, December 3, 2014 at 11:23pm
A solution is prepared by adding 1g of sugar mannitol (MW 182.2g/g-mole) in 100g of water at 20◦C. (a) Assuming that mannitol and water form an ideal solution, what is the equilibrium vapor pressure of solution? The vapor pressure of pure water is 17.54mmHg at 20◦C
Wednesday, December 3, 2014 at 8:32pm
If 325mL of a 0.58 M solution of a propanoic acid (a fatty acid) was mixed with excess glycerol what is, the maximum number of molecules of fat or oil that could result?(you will need Avogadros number = 6.022 X 10 to the 23rd power)....I need to show all work and im completely...
Wednesday, December 3, 2014 at 7:17pm
E=hv E=energy h= Planck's constant =6.626 x 10^-34 v= frequency 1. What is the energy of light having a frequency of 2.28 x 10^12? ( I do have an answer for this but I'm not so sure about it.) 2.What is the energy of light with a wavelength of 2.18 x 10^-5? 3. A photon...
Wednesday, December 3, 2014 at 7:07pm
Identify the conjugate base in the following reaction. H2O (l) + HCO31- (aq) ¨ H3O+ (aq) + CO32- (aq)? Identify the Bronsted-Lowry acid in the following reaction. H2O (l) + HCO31- (aq) ¨ H3O+ (aq) + CO32- (aq)
Wednesday, December 3, 2014 at 7:01pm
How many moles of electrons are involved in an electrolytic process if 3.07 amps are applied to the cell for 46.0 hours? The answer is 5.27, but I'm not sure how to get there. Please help!
Wednesday, December 3, 2014 at 6:50pm
A sample of steam with a mass of 0.524g and at a temperature of 100 ∘C condenses into an insulated container holding 4.20g of water at 6.0∘C.( ΔH∘vap=40.7 kJ/mol, Cwater=4.18 J/g⋅∘C) Assuming that no heat is lost to the surroundings, what is ...
Wednesday, December 3, 2014 at 5:38pm
Calculate the amount of heat required to completely sublime 71.0g of solid dry ice (CO2) at its sublimation temperature. The heat of sublimation for carbon dioxide is 32.3 kJ/mol.
Wednesday, December 3, 2014 at 4:56pm
When Pb-208 bombarded with Ni-64, a new element and six neutrons are produced. What isotope of the new element is produced by this reaction? Question 17 options: Ds-266 Ds-272 Rf-266 Rf-272 I believe it is either rf- 272 or Ds-272 because i added 208+64, but I do not know how ...
Wednesday, December 3, 2014 at 4:47pm
A mixture of ammonia and oxygen is prepared by combining 0.330 L of NH3 (measured at 0.710 atm and 22°C) with 0.200 L of O2 (measured at 0.740 atm and 51°C). How many milliliters of N2 (measured at 0.740 atm and 100. °C) could be formed if the following reaction ...
Wednesday, December 3, 2014 at 3:31pm
I'm doing a redox potential/lead acid cell experiment and one of the questions that were asked was: -What were the identities of the gases you saw being produced at the + and - electrodes during the cell conditioning process? We used H2SO4 How do I go about answering this...
Wednesday, December 3, 2014 at 1:02pm
Write out the mechanism (using correct curved arrow notation) for the acid-catalyzed, cis-trans isomerization of maleic acid (into fumaric acid) If teh electrophilic addition reaction of maleic acid with HCl had gone to completion what would be the structure of the addition ...
Wednesday, December 3, 2014 at 6:56am
When did these scientists make their contributions ? The years Democritus believes that the universe was made of tiny uncuttable particles. Heisenberg works with the Quantum Theory Chadwick finds the missing mass of the atoms nucleus Dalton's believes that atoms of a given...
Tuesday, December 2, 2014 at 10:52pm
under standard conditions, the following reaction is spontaneous at 298K. O2 + 4H+ + 4Br- --> 2H2O + 2 Br2 Will the reaction be spontaneous if the PH value is adjusted using a buffer composed of 0.10 M benzoic acid and 0.12M sodium benzoate? Given:Given: Ka for benzoic acid...
Tuesday, December 2, 2014 at 9:36pm
What is the solubility of CaF2 in a buffer solution containing 0.45M formic acid and 0.20M sodium formate? Given: Ka for formic acid=1.7x10^-4 Ka for hydrofluoric acid=6.8x10^-4 Ksp for CaF2=3.4x10^-11 Thank you so much. I don't have much idea on this.I just calculated the...
Tuesday, December 2, 2014 at 9:32pm
What volume of oxygen gas at 20.9 c and 750 torr is needed to burn 3.00 liters of propane, C3H8 at the same temprrature and pressure? I know i use V1/n1=V2/n2, but how do i get n?
Tuesday, December 2, 2014 at 8:16pm
Consider the following reaction, equilibrium concentrations, and equilibrium constant at a particular temperature. Determine the equilibrium concentration of H2O(g). C2H4(g) + H2O(g) C2H5OH(g) Kc = 9.0 × 103 [C2H4]eq = 0.015 M [C2H5OH]eq = 1.69 M
Tuesday, December 2, 2014 at 7:16pm
Kc is 1.67 × 1020 at 25°C for the formation of iron(III) oxalate complex ion: Fe3+(aq) + 3 C2O42-(aq) [Fe(C2O4)3]3-(aq). If 0.0200 M Fe3+ is initially mixed with 1.00 M oxalate ion, what is the concentration of Fe3+ ion at equilibrium?
Tuesday, December 2, 2014 at 7:05pm
The equilibrium constant, Kp, equals 3.40 for the isomerization reaction: cis-2-butene trans-2-butene. If a flask initially contains 0.250 atm of cis-2-butene and 0.145 atm of trans-2-butene, what is the equilibrium pressure of each gas?
Tuesday, December 2, 2014 at 6:54pm
The aquation of tris(1,10-phenanthroline)iron(II) in acid solution takes place according to the equation: Fe(phen)32++ 3 H3O++ 3 H2O →Fe(H2O)62++ 3 phenH+. If the activation energy, Ea, is 126 kJ/mol and the rate constant at 30°C is 9.8 × 10-3 min-1, what is ...
Tuesday, December 2, 2014 at 6:54pm
For which of these elements would the first ionization energy of the atom be higher than that of the diatomic molecule? helium oxygen carbon lithium Please explain why and thanks
Tuesday, December 2, 2014 at 6:22pm
A piece of an aluminum can was cut into small pieces. Then 0.422 g of the chips from the can was used to prepare potassium alum according to the procedure we used. Calculate the theoretical yield (in g) of potassium alum that could be obtained in the reaction. (Alum MW=474.41 ...
Tuesday, December 2, 2014 at 4:33pm
Barium-122 has a half-life of 2 minutes. If 10.0 g of Ba-122 are produced in a nuclear reactor how much Ba-122 will remain 10 minutes after production ceases? Question 11 options: 2.50 g 1.25 g 0.625 g 0.313 g
Tuesday, December 2, 2014 at 3:32pm
The half-life of I-131 is 8.00 days. If a medical treatment involves a dose of 400. mg of I-131, how much of the isotope remains after 48 days? 3.125 mg 6.25 mg 12.5 mg 25 mg
Tuesday, December 2, 2014 at 3:30pm
carbon dioxide has a henrys law constant of 3.4E-2 mol/l*atm what is the molar concentration of CO2 in water if the partial pressure of CO2 in air is .000387. i know i have to use S=Kh*P but that gives you soluability where do i go from here to find molar concentration of CO2 ...
Tuesday, December 2, 2014 at 2:59pm
26.98 grams of Al and 35.45 grams of Cl2 are reacted according to the equation 2Al + 3Cl2 → 2AlCl3 How many grams of AlCl3 will be formed assuming 100% yield? it says the answer is supposed to be 26.98g but cannot seem to reach that. I just want to know how to get there.
Tuesday, December 2, 2014 at 2:38pm
A reaction requires 0.5 g of pure methyl oleate (density = 0.87g/mL) (MW = 310g/mol). How many mL of 70% pure methyl oleate are needed for the reaction. I don't exactly know how to start this off. I think what I'm supposed to do is multiply the 70% by the molecular ...
Tuesday, December 2, 2014 at 2:10pm