Friday
October 31, 2014

Posts by Bekah


Total # Posts: 79

chem
given the thermochemical equations, B2O3 + 3H2O -> 3O2 + B2H6 delta h = -2035 kj H2O -> H2O delta h = 44 kj H2 + 1/2O2 -> H2O delta h = -286 kj 2B + 3H2 -> B2H6 delta h = 36 kj what is the delta hf for 4B + 3O2 -> 2B2O3?
October 17, 2014

chem
if the delta h for the reaction A + 2B -> C is 150 kj, delta h for 6A + 12B -> 6C is what?
October 17, 2014

chem
the work done by a gas when it expands to 96 L is 4100 J. if the external pressure is 2.0 atm, determine the initial volume of the gas.
October 16, 2014

chem
i have know idea how to even figure it out with just volume 1 and temp 1. i have tried multiple ways with the equation but not getting anywhere
October 10, 2014

chem
A sample of gas has a volume of 50 mL and an initial temperature of 380 K. The temperature must be changed to _____ K in order to halve the volume. Assume constant pressure and amount for the gas.
October 10, 2014

chem
H2 stored in a 50.0 L container has a pressure of 500.0 torr. O2 stored in a 25.0 L container has a pressure of 800.0 torr. If both these gases are released together to be stored in a 100.0 L container, what is the total pressure in the 100.0 L container?
October 10, 2014

chem
Consider the unbalanced chemical reaction Al + Cl2 → AlCl3. How many moles of AlCl3 can be obtained from 360 grams of Cl2? (Molar masses: Cl = 35.45 g/mol, Al = 26.98 g/mol) when i balance the equation i get 2Al+3Cl2->2AlCl3 but when i try to figure out the answer i ...
October 5, 2014

chem
In a chemical reaction, A and B reacts to form D. C is the intermediate product of this reaction. Percent yield of the reaction A+B->C is 50% and the percent yield of the reaction C->D is 90%. How many moles of D can be produced when 14 moles of A and B react?
October 5, 2014

chem
consider the chemical reaction, 2Al + 3Cl2 -> 2AlCl3. here, 212.7 g of chlorine can produce a maximum of 266.66 g of AlCl3 (molar mass of Al = 26.98 g and Cl = 35.45 g) true or false
October 4, 2014

chem
Consider the chemical reaction, 2Al + 3Cl2 → 2AlCl3. Here, 56 g of Al can produce 415.14 g of AlCl3 (Molar masses: Al = 26.98 g; Cl = 35.45 g). true or false
October 4, 2014

chem
the molar mass of NaCl is 58.45g. How many molecules does a gram of NaCl contain?
October 4, 2014

chem
how many moles of HCl will be produced when 30g of H2O are reacted according to the chemical equation 2AlCl3 + 3H2O -> Al2O3 + 6HCl? (molar masses are H2o=18.015g and HCl=36>46g)
October 4, 2014

chem
which of the following ions are formed when AgNO3 dissociates? a. O2- b. N3- c. AgN2- d. NO3- e. N2-
September 26, 2014

chem
A typical dose of a radioactive sample is 27.0 mCi. How long does it take for the activity to reduce to 0.100 mCi? The half life of the sample is 211,000 y.
September 19, 2014

chem
The half life of Am-241 is 432 y. If 2.00 g of Am-241 is present in a sample, what mass of Am-241 is present after 1000.0 y?
September 19, 2014

chem
If a radioactive sample has an activity of 8.33 Bq, how many disintegrations per second are occurring?
September 19, 2014

chem
A sample of radon has an activity of 80,000 Bq. If the half-life of radon is 15 h, how long before the sample's activity is 5,000 Bq?
September 19, 2014

chem
How long does it take for 10.0 g of a radioactive isotope to decay to 1.25 g if its half-life is 17.0 d?
September 19, 2014

art history
1. the center of the Renaissance 2. written backwards 3. da Vinci apprenticed for this person 4. innovative High Renaissance architect 5. the quintessential Universal man 6. city where da Vinci painted The Last Supper 2. Codex Leiceister 3. Donato Bramante 4. Andrea del ...
June 23, 2014

art history
Thanks I figured it out. Thanks for all your help tonight.
June 23, 2014

art history
3. Humanism 4. theology 1. Renaissance 5. Italy Printing press Protestant 2. Secularism 9.Paper relief Mapmaking
June 23, 2014

art history
1. During the ______, the writings and art of Ancient Greeks were rediscovered. 2. ______ is the study of religious faith, practice and experience. 3. Renaissance thinkers promoted _______, individualism, and secularism. 4. _______ is the idea that people should be more ...
June 23, 2014

art history
You told me 1 and 3 but thank you so much.
June 23, 2014

art history
Number 2 is Albert durer
June 23, 2014

art history
Oops that's Albert durer
June 23, 2014

art history
I have 7 also
June 23, 2014

art history
This is different questions. I never got answers to these. I have 1 through 4. I need help on the rest.
June 23, 2014

art history
1. art enabled new understandings in this field (the protestant reformation) 2. credited with being the founder of Renaissance painting in the Netherlands distance 3. his most famous painting depicts sin and redemption (genre) 4. he brought Germany into the mainstream of ...
June 23, 2014

art history
Thanks I have all except 3 and 4, can you help me with those please?
June 23, 2014

art history
Distance Parallel Vanishing Hieronymus bosch Jan van Eyck Albrecht Düre Mathematical polyptch
June 23, 2014

art history
1. Art enabled new understandings in this field 2. Credited with being the founder of Renaissance painting in the Netherlands 3. his most famous painting depicts sin and redemptionhe 4. brought Germany into the mainstream of Renaissance art 5. objects appear to get smaller ...
June 23, 2014

chemistry
Match the name or structure with its functional group. Each molecule has only one functional group. My choices are alkane, alcohol, alkyne, carboxylic acid, alkene, aldehyde, ketone, ester, and ether. 1. 2-propanol- alcohol 2. 2-methoxypentane- alkane 3. formaldehyde- aldehyde...
May 10, 2014

chemistry
This functional group can be generated by oxidation of an aldehyde. Oxidation is just the reaction with oxygen, but unlike combustion you are not producing carbon dioxide and water.
May 10, 2014

chemistry
This type of functional group is often sweet smelling and may be used as a fragrance. When it reacts with water it will produce a carboxylic acid and an alcohol. I chose ester but it is wrong
May 10, 2014

chemistry
For each organic compound, determine if it is an alkane, alkene, or alkyne. (No ringed structures and only one multiple bond per structure.) 1. C10H18 - alkyne 2. C15H32 - alkane 3. C20H40 - alkyne 4. C5H10 - alkene 5. C3H6 - alkene 6. C7H16 - alkane I am not sure on number 3
May 6, 2014

chemistry
the answers i have tried are F,F,T,T and F,F,T,F
May 5, 2014

chemistry
The cell shown above is a concentration cell. Both cells contain a copper solution and have copper electrodes. The only driving force for this cell is the difference in the concentration of the copper solutions. The system will react to equalize the concentration of the ions ...
May 5, 2014

chemistry
How many grams of copper will be deposited at the cathode of an electrolytic cell if a current of 680.0 mA is run through a 2.5 M solution of copper sulfate for 20.0 minutes?
May 5, 2014

chemistry
For the reaction, shown below, determine which statements are True and which are False. 3Fe(s) + Cr2O72-(aq) +14H+(aq) → 3Fe2+(aq) + 2Cr3+(aq) + 7H2O(l) ξo=1.77V 1. The oxidizing agent is dichromate (Cr2O72-). 2. The iron half-reaction takes place in an acidic ...
May 2, 2014

chemistry
Construct a galvanic (voltaic) cell from the half reactions shown below. Au3+ + 3 e- → Au (s) ξo= 1.420 V Br2 (l) + 2 e-→ 2 Br- (aq) ξo= 1.087 V Calculate the equilibrium constant (K) for this cell. Assume that the temperature is 298K. First, consider ...
May 2, 2014

chemistry
Consider the following standard reduction potentials of some commonly used metals: ξo (V) Au3+ (aq) + 3 e- → Au (s) +1.50 Ag+ (aq) + e- → Ag (s) +0.80 Cu2+ (aq) + 2e- → Cu (s) +0.34 Fe3+ (aq) + 3e- → Fe (s) -0.036V Al3+ (aq) + 3e- → Al (s) -1...
May 2, 2014

chemistry
Use the following pair of reduction half-reactions to design a galvanic cell. Then write in the proper coefficient for each of the species involved in the overall reaction. Water molecules and protons are not shown in the half-reactions, but may be needed in the overall ...
May 2, 2014

chemistry
Under standard conditions, the Gibbs free energy of the reactants G,std(reactants) in a reaction in the gas phase is 232.94 kJ and the Gibbs free energy of the products G,std(products) is 211.56 kJ. Calculate the value of the equilibrium constant for this reaction under ...
April 28, 2014

chemistry
i am using dG=dH-tdS and i have tried dG-dH/T,dG/dH+T,dG/dH-T. My answers are -1.33,-1.0E3, -1.01E2
April 24, 2014

chemistry
What is the standard entropy of reaction, the standard entropy of reaction, in J/K, for the combustion reaction of ethylene described in the previous questions? The temperature is 298.15K. (Enter your answer as a signed number in scientific notation without units.) My answers ...
April 24, 2014

chemistry
Adding a complex ion forming species to a solution will increase the solubility of a slightly soluble species. Calculate the Molar solubility (s) of AgI in a 1.75 M ammonia solution. The Ksp for AgI is 8.3 x 10-17 and the Kf for Ag(NH3)2+ is 1.5 x 107. I have tried getting ...
April 14, 2014

chemistry
i figured it out
April 12, 2014

chemistry
A 1.0 L solution has 10.00 grams of CaCl2 dissolved in it. What is the Molar solubility of AgCl in this same solution? The Ksp for AgCl is 1.6 x 10-10 at this temperature. Hint: watch out for the common ion again.
April 12, 2014

chemistry
It is possible to manipulate the solubility of some compounds through pH adjustments. What is the appropriate pH that will yield a Molar solubility for Mg(OH)2 of 2.51 x 10-8? The Ksp for Mg(OH)2 is 1.2 x 10-11. (Hint: you may assume the concentration of hydroxide is constant ...
April 12, 2014

chemistry
My original sample of mixed salt had a mass of 8.9 grams. After heating the mixture in the crucible and weighing it multiple times my final mass of salt ended up being 4.9. How many moles of oxygen were driven off? Lost on how to do this been a while since I have done this.
April 1, 2014

chemistry
If my original sample contained 7.1 grams of potassium chlorate. How many moles of oxygen gas would I expect to have evolved? Hint: Convert grams to moles of potassium chlorate, then use the mole ratio in the balanced equation. Balance this equation KClO3 → KCl + O2(g) I...
April 1, 2014

chemistry
A 1.0 M acetic acid solution (CH3COOH, pKa = 4.7) is neutralized by dissolving NaOH(s) (a strong base) in the solution. Estimate the pH at the equivalence point of the neutralization process: 4.7 7.0 9.3 Which one of the following statements best explains your prediction? 1. ...
March 31, 2014

chemistry
Select only the True statements about buffer systems. Select all that are True. 1. Starting with NH3(aq) and adding a small amount of HCl(aq) will make a buffered solution. 2. The blood buffer, among other things, is supported by carbonic acid and its conjugate base ...
March 28, 2014

chemistry
enzoic acid is a weak monoprotic acid with Ka = 6.5×10-5 M. NaOH(s) was gradually added to 1.00 L of 8.66×10-2 M benzoic acid. 1. Calculate the pH of the solution before the addition of the base. 2. Calculate the pH of the solution after the addition of 5.20×...
March 25, 2014

chemistry
Consider a buffer solution consisting of CH3NH3Cl and CH3NH2. Which of the following statements are true concerning this solution? (Ka for CH3NH3+ = 2.3 x 10 -11). 1. A solution consisting of 0.1 M CH3NH3Cl and 0.1 M CH3NH2 would be a more effective buffer than one containing ...
March 25, 2014

chemistry
Consider the titration of 50.0 mL of 0.200 M HOCl by 0.200 M KOH for the next five questions (Ka for HOCl = 3.5 x 10-8). Calculate the pH after 150.0 mL of KOH has been added.
March 23, 2014

math
n+3.4<5.8
February 13, 2014

physics
Joe stands on a bridge kicking stones into the water below. If he kicks a stone with a horizontal velocity of 3.10 m/s, and it lands in the water a horizontal distance of 6.60 m from where Joe is standing, what is the height of the bridge? Enter m as unit. Draw the problem.
December 5, 2011

English
is this true:Introductory participial phrases and adverb clauses are set off from main clauses by commas.
October 27, 2011

College Chemistry
when a 0.702g sample of a mixture of volatile hydrocarbons is burned in a bomb calorimeter with a heat capacity of 4287 J/C, the temperature rises by 4.72 degrees C. How much energy (in kilojoules) is released during combustion?
October 25, 2011

College Chemistry
Write formation reactions for the following. (You must include the states of matter for each atom or compound) A. Ca(NO3)2 (s) B. CH3OH (l) C. NaClO4(s)
October 25, 2011

College Chemistry
How many milliliters of 0.100 M HNO3 are needed to neutralize the following solutions? A. 45.0 mL of 0.667 M KOH B. 58.5 mL of 0.0100 M Al(OH)3
October 6, 2011

College Chemistry
Calculate the concentrations of the following solutions, assuming the volumes are exact measurements: a. 18.64g of sodium hydroxide in 350mL of solution b. 8.97mL of 18M hydrochloric acid in 250mL of solution
October 4, 2011

chemistry
Solubility and Precipitation: 1. Alkali Metal Cations, ammonium cations= Soluble. 2. Nitrate Anions, Acetate Anions= Soluble. 3. Halogen anions= Soluble...except: Ag+, Cu+, Hg2 +2, and Pb+2. 4. Sulfate Anions= Soluble...except: Ba +2, Ca+2, Hg2 +2, Pb+2, Sr+2. 5. Anything else...
October 4, 2011

College Chemistry
Zinc, copper, lead, and mercury ions are toxic to Atlantic salmon at concentrations of 6.42 times 10 to the -2 mM, 7.16 times 10 to the -3 mM, 0.965 mM, and 5.00 times 10 to the -2 mM, respectively. What are the corresponding concentration is milligrams per liter? A. ...
October 2, 2011

College Chemistry
How many grams of solute are needed to prepare each of the following solutions? A. 1.000 L of 0.180 M NaCl B. 250.0 mL of 0.150 M CuSO4 C. 500.00 mL of 0.355 M CH3OH
October 2, 2011

Chemistry
Iron (II) ions can be precipitated from the following reaction: 4Fe(OH)+(aq) + 4OH-(aq) + O2(g) + 2H2O(l) --> 4Fe(OH)3(s) How many grams of oxygen gas will be needed to precipitate the iron contained in 125mL of 0.085M Fe(OH)+ solution?
September 28, 2011

chemistry
What is the concentration, in units of molarity, of a 350 mL solution containing 0.298 moles of sodium chloride in water?
September 27, 2011

college math
Step 1: Eric = 1/2 of Dans; Eric + Dan = 18 Step 2: 12 + 6 = 18 Step 3: Eric has to be 6 because half of 12 is 6 and when you add them together you 18. Step 4: Equation- Part A: D = 12; E = 1/2D; T= 18. Equation- Part B: E + D = T so... 1/2D + D = 18!!!! enjoy!
September 27, 2011

chemistry
A 8.00 M solution of hydrochloric acid is provided. You need to make 25.0 mL of a 0.490 M HCl solution. What volume, in mL, of the 8.00 M solution should you use?
September 27, 2011

ap bio
The number of trophic levels that can be maintained in an ecosystem is limited by: a. a gain in population size b. the loss of potential energy c. the number of individuals in the ecosystem i have chosen a but it is for a grade and i would love some help?? :)
August 27, 2011

calc
thank you so much!!!!
January 2, 2011

calc
can you just show me how to set this up? or a formula that could help? im confused. The length of a rectangle is increasing at 3 ft/min and the width is decreasing at 2 ft/min. When the length is 50 ft and the width is 20 ft, at what rate is the rectangle decreasing?
January 2, 2011

biology
What is the variable being tested in an experiment called?
December 14, 2010

Geometry
the info of about the circle is irrelevent. Since the triangel is isosceles than that means another side of it is 4r. Find the missing side then use the area of a triangle formula!
December 14, 2010

algebra
-72/14*14/-72 (cross multiply) ?
December 14, 2010

math
R because the others all have set limitations. R is the only one that makes sense! Since numbers can go on forever that means numbers greater than 18 would be infinite!
December 13, 2010

history-multiple choice
e
April 8, 2009

ponctuation, mechanisme, and writing
First off, it is one thing to ask for assistance because you do not understand something. It is a completely different thing for someone to give you all of the answers. It really is your loss though, because instead of getting the reasoning why and understanding, you are just ...
November 27, 2008

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