Monday
September 22, 2014

Posts by gabriella


Total # Posts: 156

AP Chemistry
Use the Clausius-Clapeyron equation to calculate the temperature at which pure water would boil at a pressure of 367 torr. The heat of vaporization of water is 43105 J/mol at 100◦C. Answer in units of ◦C
March 5, 2014

AP Chemistry
Benzene is a hydrocarbon that is commonly used as a commercial solvent. However, it is carcinogenic; i.e., accumulations in the body can cause cancer. What is the vapor pressure of benzene at 58◦C? The normal boiling point of benzene is 80.0◦C and its molar heat of...
March 5, 2014

AP Chemistry
The rate of effusion of unknown gas X is found to be about 1.5 times that of SF6 gas (MW=146 g/mol) at the same conditions of temperature and pressure. What is the molecular weight of gas X? Answer in units of g/mol
February 16, 2014

AP Chemistry
A 1277 mL sample of nitrogen (N2) was collected by displacement of water at 24 degrees C under a total barometric pressure of 966 torr. What mass of dry nitrogen was collected? The vapor pressure of water at 24 degrees C is 22 torr. Answer in units of g
February 16, 2014

AP Chemistry
Part 1 of 3: An apparatus consists of a 2 L flask containing nitrogen gas at 30 degrees C and 758 kPa, joined by a valve to a 11 L flask containing argon gas at 30 degrees C and 49.7 kPa. The valve is opened and the gases mix. What is the partial pressure of nitrogen after ...
February 16, 2014

AP Chemistry
We drop 30 grams of magnesium into 770 mL of a 4 M HCl solution. What is the maximum volume of dry hydrogen that could be produced by this reaction at STP? Mg(s) + 2HCl(aq)→MgCl2(aq) + H2(g) Answer in units of liters
February 16, 2014

AP Chemistry
Iron pyrite (FeS2) is the form in which much of the sulfur exists in coal. In the combustion of coal, oxygen reacts with iron pyrite to produce iron(III) oxide and sulfur dioxide, which is a major source of air pollution and a substantial contributor to acid rain. What mass of...
February 16, 2014

AP Chemistry
We observe that 5 grams of a gaseous com- pound occupies 2083 mL at 50 degrees C and 574 torr. What is the molecular weight of the compound? Answer in units of g/mol
February 16, 2014

AP Chemistry
A 2.8 gram sample of a gaseous substance occupies 12 L at 47 degrees C and 683 torr. What is the density of the gas under these conditions? Answer in units of g/L
February 16, 2014

AP Chemistry
What pressure would a mixture of 3.2 grams of O2, 6.4 grams CH4, and 6.4 grams of SO2 exert if the gases were placed in a 4.1 liter container at 127 degrees C? Answer in units of atm
February 16, 2014

AP Chemistry
Nitroglycerin is a shock-sensitive liquid that detonates by the reaction 4C3H5(NO3)3(ℓ)-> 6N2(g)+10H2O(g)+12CO2(g)+O2(g) Calculate the total volume of product gases at 201 kPa and 273 degrees C from the detonation of 3.3 lb (1496.9 g) of nitroglycerin. Answer in units...
February 16, 2014

AP Chemistry
To what temperature must a sample of helium gas be cooled from 110 degrees C to reduce its volume from 4.9 L to 0.7 L at constant pressure? Answer in units of K
February 16, 2014

AP Chemistry
what is the pKa of an acid that has a pH of 7.4 at neutralization and has to have 25 mL added to neutralize it
February 5, 2014

ap chemistry
What is the ratio of the molarities of PO3^4- and HPO4^2− ions in a buffer solution having a pH of 13.16? What mass of K3PO4 must be added to 1 L of 0.1 M K2HPO4(aq) to prepare a buffer solution with a pH of 13.16? Answer in units of g What mass of K2HPO4 must be added ...
February 4, 2014

ap chemistry
What is the pH at the equivalence point in the titration of 10.0 mL of 0.56 M HZ with 0.200 M NaOH? Ka = 6.6 × 10−5 for HZ.
February 4, 2014

ap chemistry
What is the pH at the point during a titration when 34 mL of 0.200 M HCl has been added to 29 mL of 0.0500 M NH3 solution? HCl is a strong acid, Kb=1.8×10−5 for NH3. Answer in units of pH
February 4, 2014

ap chemistry
these questions are followups of the original questin posted. How much base much be added to make the solution equalized? Answer in units of mL What is the pKa for this acid?
February 4, 2014

ap chemistry
Calculate the pH at the equivalence point for the titration of a solution containing 150.0 mg of ethylamine (C2H5NH2) with 0.1000 M HCl solution. The volume of the solution at the equivalence point is 250.0 mL. Kb for ethylamine is 4.7 × 10−4.
February 4, 2014

ap chemistry
Calculate the ratio of [NH3]/[NH4+] that gives a solution of pH = 10.60.
February 4, 2014

ap chemistry
How many moles of sodium acetate (NaCH3COO) must be added to 1.000 liter of a 0.500M solution of acetic acid (CH3COOH) to produce a pH of 5.027? The ionization constant of acetic acid is 1.8 × 10−5. Answer in units of mol
February 4, 2014

ap chemistry
The ionization constant of HF is 7.2 × 10−4. What is the molar concentration of H+ in a solution which is 0.353 molar in HF and 0.145 molar in KF?
February 4, 2014

ap chemistry
What mass of solid sodium formate (of MW 68.01)must be added to 125 mL of 0.48 mol/L formic acid (HCOOH) to make a buffer solution having a pH of 4.07? Ka = 0.00018 for HCOOH. Answer in units of g
February 4, 2014

ap chemistry
What is the concentration of hydrogen ions in a solution containing 0.785 M HOCN (cyanic acid) and 0.659 M (NaOCN) (sodium cyanate)? The ionization constant of cyanic acid is 3.5 × 10−4. Answer in units of M
February 4, 2014

ap chemistry
What is the concentration of H+ ions in a buffer solution containing 0.305 M benzoic acid (with ionization constant 6.5 × 10−5)and 0.834 M sodium benzoate (a salt of benzoic acid)?
February 4, 2014

ap chemistr
The ionization constant of HA is 1×10−6. What must be the ratio of [A−] to [HA] for the preparation of a buffer solution with a pH of 5.74?
February 4, 2014

ap chemistry
A buffer solution is made by dissolving 0.45 moles of a weak acid (HA) and 0.23 moles of KOH into 680 mL of solution. What is the pH of this buffer? Ka = 2.4×10−6 for HA.
February 4, 2014

AP Chemistry
If 435 mL of 2.7 molar HCl solution is added to 128 mL of 3.2 molar Ba(OH)2 solution, what will be the molarity of BaCl2 in the resulting solution? Answer in units of M
January 30, 2014

AP Chemistry
If 400 mL of 3.2 molar HCl solution is added to 300 mL of 2 molar NaOH solution, what will be the molarity of NaCl in the resulting solution? Answer in units of M
January 30, 2014

AP Chemistry
A 65 mL sample of a solution of sulfuric acid is neutralized by 46 mL of a 0.14 M sodium hydroxide solution. Calculate the molarity of the sulfuric acid solution. Answer in units of mol/L
January 30, 2014

AP Chemistry
How many moles of NaOH will it take to neutralize 0.77 L of 0.81 M HCl? Answer in units of mol
January 30, 2014

AP Chemistry
50.0 mL of an HCl solution with a pH of 3.5 neutralizes 200.0 mL of a Ca(OH)2 solution. What is the molarity of the Ca(OH)2 solution?
January 30, 2014

AP Chemistry
Which one of the following compounds is not a salt? 1. Ca(ClO4)2 2. Fe(NO3)3 3. Cr(OH)3 4. Na2SO3 5. KMnO4
January 30, 2014

algebra 2
Cube root (x+8)-6=-2
January 28, 2014

algebra 2
3(x-2)^4=24
January 28, 2014

AP Chemistry
A 0.00100 M solution of a weak acid HX is 6% ionized. Calculate Ka for the acid.
January 24, 2014

AP Chemistry
I tried .15 and it said it was incorrect.
January 24, 2014

AP Chemistry
I got the first two parts correct but I can't seem to get the last part. The concentration I got for H3O^+ is 1.151520734e-3. When I plugged that in for the %ion I got 0.1476308633. I typed that into my homework and it said that is incorrect.
January 24, 2014

AP Chemistry
A given weak acid HZ has a Ka=1.7×10−6. What is the H3O+ concentration of a solution of HZ that has a concentration of 0.78 mol/L? What is the pH of this solution of HZ? What is the percent ionization of HZ in this solution? Answer in units of %
January 24, 2014

AP Chemistry
What is the pH of a 0.41 M solution of pyridinium chloride (C5H5NH+Cl−)? (Kb for pyridine is 1.5×10−9.) Answer in units of pH
January 24, 2014

AP Chemistry
Consider the ionization constants cyanic acid (HOCN) : Ka= 3.5×10−4; ammonia (NH3): Kb= 1.8×10−5. A solution of ammonium cyanate (NH4OCN) is 1. acidic, because the cation and the anion hydrolyze to the same extent. 2. acidic, because the anion ...
January 24, 2014

AP Chemistry
Like all equilibrium constants, Kw varies somewhat with temperature. Given that Kw is 7.51×10−13 at some temperature, compute the pH of a neutral aqueous solution at that temperature.
January 24, 2014

AP Chemistry
The pH of a solution of hydrochloric acid is 1.67. What is the molarity of the acid? Answer in units of mol/L
January 21, 2014

AP Chemistry
The ionic substance T3U2 ionizes to form T2+ and U3− ions. The solubility of T3U2 is 4.07×10−20 mol/L. What is the value of the solubility-product constant?
January 9, 2014

AP Chemistry
What is the value of Ksp for Ag2SO4 if 5.70 g is soluble in 1.00 L of water?
January 9, 2014

AP Chemistry
Calculate the solubility product constant for calcium carbonate, given that it has a solubility of 5.3×10^7 g/L of water.
January 8, 2014

AP Chemistry
A solution of AgI contains 1.2 mol/L Ag+. Ksp of AgI is 8.3×10^17. What is the maximum I− concentration that can exist in this solution? Answer in units of mol/L
January 8, 2014

AP Chemistry
Calculate the concentration of Hg2+ ions in a saturated solution of HgS(s). (Ksp=1.7×10^52) Answer in units of mol/L What volume of solution contains one Hg2+ ion? Answer in units of L/ion
January 8, 2014

English
1. C 2. A 3. A these should be correct.
January 8, 2014

AP Chemistry
The system CO2(g) + H2(g)<->H2O(g) + CO(g) is at equilibrium at some temperature. At equilibrium a 4.00 L vessel contains 1.00 mole CO2, 1.00 mole H2, 2.40 moles H2O, and 2.40 moles CO. How many moles of CO2 must be added to the system to bring the equilibrium CO ...
December 2, 2013

AP Chemistry
A mixture consisting of 1 mol of H2O(g) and 1 mol CO(g) is placed in a 11 L reaction vessel at 800 K. At equilibrium, 0.422 mol CO2(g) is present as a result of the reaction CO(g) + H2O(g)<->CO2(g) + H2(g). What is Kc at 800 K?
November 27, 2013

AP Chemistry
The equilibrium constant for the reaction PCl3(g) + Cl2(g)<-> PCl5(g) is 35000 at 760◦C. At equilibrium, the partial pressure of PCl5 was 110 bar and that of PCl3 was 9.98 bar. Calculate the equilibrium partial pressure of Cl2. Answer in units of bar
November 27, 2013

AP Chemistry
At 350 K, Kc= 0.142 for the reaction 2BrCl(g)<-> Br2(g) + Cl2(g) An equilibrium mixture at this temperature contains equal concentrations of bromine and chlorine, 0.049 mol/L. What is the equilibrium concentration of BrCl? Answer in units of M
November 27, 2013

AP Chemistry
At a certain temperature, the equilibrium constant Kc is 0.154 for the reaction 2SO2(g) + O2(g)<-> 2SO3(g) What concentration of SO3 would be in equilibrium with 0.250 moles of SO2 and 0.885 moles of O2 in a 1.00 liter container at this temperature? Note: These latter ...
November 27, 2013

AP Chemistry
The equilibrium constant for thermal dissociation of F2 F2(g)<->2F(g) is 0.300. If initially 1.00 mol F2 is placed in a 1.00 L container, which of the following is the correct number of moles of F2 that have dissociated at equilibrium? 1. 0.130 mol 2. 0.418 mol 3. 0.548 ...
November 26, 2013

AP Chemistry
I got an answer of 0.226, now I need to know what the spontaneous direction of change is. It went from 0.278 to 0.226.
November 26, 2013

AP Chemistry
Analysis of a reaction mixture showed that it had the composition 0.43 mol/L N2, 0.541 mol/L H2, and 0.124 mol/L NH3 at 800 K, at which temperature Kc=0.278 for N2(g) + 3H2(g)<->2NH3(g). Calculate the reaction quotient Qc
November 26, 2013

AP Chemistry
The equilibrium constant Kp is 5.00×10^17 at 25◦C for the reaction C2H4(g) + H2(g)<->C2H6(g). From this information, calculate ∆G0 at 25◦C
November 26, 2013

ap chemistry
What is the activation energy Ea for this reaction? Answer in units of kJ The deltaH is 160 kJ X is at 160 (beginning of reaction) Y is at 300 (end of reaction)
November 16, 2013

math
A circular swimming pool has radius of 15 feet. The family that owns the pool wants to erect a circular fence that is 5 feet away from the pool. Which is the closest to the circumference of the fence they will need? A. 94.2 ft B. 125.6 ft C. 157 ft D. 188.4 ft
November 14, 2013

ap chemistry
Under certain conditions, the reaction 3A + 2B -> 4C was observed to proceed at a rate of 0.00348 M· s−1. What was the corresponding rate of change in reactant A?
November 6, 2013

AP Chemistry
Calculate the standard entropy change for the dimerization of NO2: 2NO2(g)→N2O4(g)at 298 K, if S◦ ∆H◦f J/K·mol NO2(g) 240.06 33.18 N2O4(g) 304.29 9.16 Answer in units of J/K·mol
October 29, 2013

AP Chemistry
This temperature represents the freezing point of ethanol. (Which means delta G = 0) What is the entropy change for the vaporization of 3.3 mol H2O(ℓ) at 100◦C and 1 atm? ∆H= 40700 J/mol. Answer in units of J/K
October 29, 2013

AP Chemistry
Calculate the entropy change when 4.44g of H2 reacts with O2 according to the reaction 2H2(g) + O2(g)→2H2O(ℓ) at 298 K and 1 atm pressure. The stan- dard molar enthalpy of formation of H 2O(ℓ) at 298 K is −285.8 kJ/mol. The corresponding free energy of ...
October 29, 2013

AP Chemistry
Calculate ∆G0 for the following reaction. 4XY + 3Z2−→2Z3X2+ 2Y2 Substance ∆H0f S0kJ/mol J/mol·K XY 205.0 75.0 Y2 −82.0 37.0 Z2 −25.0 78.0 Z3X2 −245.0 137.0 Answer in units of kJ/mol
October 29, 2013

Ap chemistry
The standard enthalpy of formation of Mn2O3 is −962.3 kJ/mol. How much heat energy is liberated when 6.4 grams of man- ganese are oxidized by oxygen gas to Mn2O3 at standard state conditions? Answer in units of kJ
October 29, 2013

AP Chemistry
I'm plugging that into my calculator and when I plug it into the answer box it keeps telling me that the answer is incorrect.
October 24, 2013

AP Chemistry
The standard enthalpy of formation of Mn2O3 is −962.3 kJ/mol. How much heat energy is liberated when 6.5 grams of manganese are oxidized by oxygen gas to Mn2O3 at standard state conditions? Answer in units of kJ
October 24, 2013

ap chemistry
For the first question, the answer I got was -20665.3 kJ and it was correct. However, every time I plug that answer into the equation I get the wrong answer for the second question. I've converted the aforementioned number into joules but I still got the wrong answer when ...
October 22, 2013

ap chemistry
Suppose that coal of density 1.5 g/cm3 is pure carbon. (It is, in fact, much more complicated, but this is a reasonable first approximation.) The combustion of carbon is described by the equation C(s) + O2(g) −! CO2(g) H◦ = −394 kJ What is the value of q...
October 22, 2013

ap chemistry
How much heat is required to heat 19 g of solid silver from 100 ◦C to liquid silver at 961◦C? The specific heat of solid silver is 0.235 J/g ·◦ C, and the heat of fusion of silver at its melting point of 961◦C is 11.3 kJ/g. Answer in units of kJ
October 22, 2013

ap chemistry
Consider the specific heats CH2O(s) = 2.09 J/g ¡¤◦ C. CH2O(§¤) =4.18 J/g ¡¤◦ C. CH2O(g) = 2.03 J/g ¡¤◦ C. The heat of fusion for water is 334 J/g and the heat of vaporization for water is 2260 J/g. Calculate ...
October 22, 2013

ap chemistry
Consider the specific heats H2O(s) =2.09 J/g ¡¤◦C,H2O (§¤) = 4.18 J/g ¡¤◦C, and H2O(g) = 2.03 J/g ¡¤◦C. The heat of fusion for water is 334 J/g and its heat of vaporization is 2260 J/g. Calculate the amount ...
October 22, 2013

ap chemistry
When 0.515 g of compound X is burned completely in a bomb calorimeter containing 3000 g of water, a temperature rise of 0.243◦C is observed. What is Urxn for the combustion of compound X? The hardware component of the calorimeter has a heat capacity of 3.12kJ/◦...
October 22, 2013

ap chemistry
A sample of 1.67 grams of Z is dissolved into 500 grams of water which is in a Styrofoam coffee cup. The temperature is monitored and is found to rise from 25.594◦C to 26.041◦C. What is Hsolution for substance Z? Assume no heat is lost/gained by the cup itself...
October 22, 2013

ap chemistry
Calculate the energy required to heat 827 g of mercury from 37 ◦C to 42 ◦C. The specific heat capacity of Hg(§¤) is 0.138 J/g ¡¤◦ C. Answer in units of calories
October 22, 2013

AP Chemistry
where did you get the 6.6 from? and i did the work correctly and the answer was wrong.
October 11, 2013

AP Chemistry
How much work is done by the system when 2.00 moles of O2 expand from a volume of 3.00 liters to a volume of 9.6 liters against a constant external pressure of 0.0100 atm answer in units of joules
October 11, 2013

AP Chemistry
Convert 8.3×10^5 cal to kiloJoules
October 11, 2013

AP Chemistry
What volume of natural gas does this correspond to at 25◦C and 0.8 atm? Answer in units of L I could not find the answer to the question above but this question uses the answer to the other question. So can you please help me.
October 11, 2013

AP Chemistry
Okay. I did each of these steps and I didn't get the correct answer.
October 11, 2013

AP Chemistry
i don't know equation to use.
October 11, 2013

AP Chemistry
A typical bathtub can hold 93 gallons of water. Calculate the mass of natural gas that would need to be burned to heat the water for a tub of this size from 60◦F to 99◦F. Assume that the natural gas is pure methane(CH4) and that the products of combustion are ...
October 11, 2013

AP Chemistry
a student titrates three samples of 0.3% hydrogen peroxide solution made from a bottle of 3% hydrogen peroxide solution dated 10/31/2007. would you expect the calculated molarities of the samples to be higher or lower than the following values: trial 1: .0015 molar trial 2: ....
October 5, 2013

AP Chemistry
no
October 4, 2013

AP Chemistry
assuming a density of 1.0 g/mL, calculate the molarity and mole fraction of 3.0% h2o2
October 4, 2013

AP Chemistry
A total charge of 96.5 kC is passed through an electrolytic cell. What mass of copper will be produced from a copper(II) chloride solution? Answer in units of g
September 28, 2013

ap chemistry
A total charge of 96.5 kC is passed through an electrolytic cell. What mass of silver metal will be produced from a silver nitrate solution? Answer in units of g
September 28, 2013

ap chemistry
Find the equilibrium constant for the reaction Cr(s) + Zn2+(aq)→Cr2+(aq) + Zn(s) if the standard cell emf is −0.76 V at the cathode and −0.91 V at the anode. RT - F= 0.025693 V
September 27, 2013

AP Chemistry
Pb(s)|PbSO4(s)|SO2−4(aq,0.60 M)||H+(aq,0.70 M)|H2(g,192.5 kPa)|Pt. If E◦for the cell is 0.36 V at 25◦C, write the Nernst equation for the cell at this temperature. out of the five following choices, which one is correct 1.E= 0.36 + 0.01285 ln 192.5(0.70)2(0....
September 26, 2013

AP Chemistry
For the reduction of Cu2+by Zn, ∆G◦=−212 kJ/mol and E◦= +1.10 V. If the coefficients in the chemical equation for this reaction are multiplied by 2, ∆G◦=−424 kJ/mol. This means E◦= +2.20 V. True or false?
September 26, 2013

ap chemnstry
What is the standard reaction free energy if the standard cell emf is 1.23? Faraday’s constant is 96485 C/mol. Answer in units of kJ/mol
September 26, 2013

AP Chemistry
Calculate the standard cell emf for galvanic cells with the cell reaction 2H2(g) + O2(g)→2H2O(ℓ)in acidic solution. Answer in units of V
September 26, 2013

AP Chemistry
redox reaction: Hydrogen peroxide is added to an acidified solution of potassium permanganate. what is the total redox reaction?
September 23, 2013

ap chemistry
Write the half reactions and the balanced equation for the galvanic cell Hg(ℓ)|Hg2+2(aq)||MnO4(aq),Mn2+(aq),H+(aq)|Pt(s). What is the smallest possible integer coefficient of H2O(ℓ) in the combined balanced equation?
September 16, 2013

AP Chemistry
Na half-cell potential is -2.71 K half-cell potential is -2.92 and yes that is all of the problem
September 13, 2013

AP Chemistry
Given the Na+/Na and K+/K half-cells, determine the overall electrochemical reaction that proceeds spontaneously and the E0 value. Answer in units of V
September 13, 2013

AP Chemistry
What volume of water was added to the 350 mL of NaOH solution? Assume volumes are additive. Answer in units of mL
September 11, 2013

AP Chemistry
An unknown amount of water is mixed with 350 mL of a 6 M solution of NaOH solution. A 75 mL sample of the resulting solution is titrated to neutrality with 52.5 mL of 6 M HCl. Calculate the concentration of the diluted NaOH solution. Answer in units of M
September 11, 2013

AP Chemistry
Listerine mouthwash is 21.6% ethyl alcohol by volume. What mass of ethanol is contained in 20.0 mL of mouthwash? (The density of ethanol is 0.789 g/mL.) Answer in units of grams
September 11, 2013

AP Chemistry
We add excess Na2CrO4 solution to 68.0 mL of a solution of silver nitrate (AgNO3) to form insoluble solid Ag2CrO4. When it has been dried and weighed, the mass of Ag2CrO4 is found to be 0.270 grams. What is the molarity of the AgNO3 solution? Answer in units of M
September 11, 2013

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