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December 19, 2014

Homework Help: Science: Chemistry

Recent Homework Questions About Chemistry

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Physical Chemistry
A pharmaceutical preparation of pH 6.2 is preserved with substance A (pKa 8.5). If the preservative effect is due to the undissociated molecule determine the per cent of active preservative present in the preparation. Thanks! :)
Friday, November 29, 2013 at 2:48pm

Chemistry
Weak polyprotic acids are normally added to Coca Cola to lower its pH to about 2.5 and impart tartness? Show that a two litter cocacola bottled drink that contains 0.057 to 0.084 percent of 75 percent of phosphoric acid by mass,meets this ph requirement. Pka1= 2.12
Friday, November 29, 2013 at 2:02pm

Chemistry
Weak polyprotic acids are normally added to Coca Cola to lower its pH to about 2.5 and impart tartness? Show that a two litter cocacola bottled drink that contains 0.057 to 0.084 percent of 75 percent of phosphoric acid by mass,meets this ph requirement. Pka1= 2.12
Friday, November 29, 2013 at 2:02pm

Chemistry
Determine The Mole Fraction Of Substances In Solution Containing 36g of water and 46g of glaycerine C3H5(OH)3.
Friday, November 29, 2013 at 12:27am

Chemistry
Determine The Mole Fraction Of Substances In Solution Containing 36g of water and 46g of glaycerine C3H5(OH)3.
Friday, November 29, 2013 at 12:25am

chemistry
A cylindrical glass of water (H2O) has a radius of 6.12 cm and a height of 9.91 cm. The density of water is 1.00 g/cm3. How many moles of water are contained in the glass?
Thursday, November 28, 2013 at 3:02pm

Chemistry
Is oxygen considered an diatomic molecule?
Wednesday, November 27, 2013 at 7:39pm

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?
Wednesday, November 27, 2013 at 5:04pm

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
Wednesday, November 27, 2013 at 5:02pm

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
Wednesday, November 27, 2013 at 5:00pm

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 ...
Wednesday, November 27, 2013 at 4:59pm

Analaytical Chemistry
ahhh
Wednesday, November 27, 2013 at 7:47am

Chemistry
What is 0.7g of SO2 ..and how would you do this equation? Thanks,
Wednesday, November 27, 2013 at 7:28am

Chemistry
How many moles in 0.7g of SO2 ..and how would you do this! Thanks
Wednesday, November 27, 2013 at 7:27am

Chemistry
6. Explain how you would prepare this solution from powdered reagents and whatever glassware you needed: 3.0 L of 1.3 M NaOH
Wednesday, November 27, 2013 at 4:46am

Chemistry- DrBob222 Urgent Please help
Name these: a) CH2=CH-CH=CH2 b) CH3-CH=CH-C(TRIPLE BOND)CH c) CH3-CH2-CH2-CH(Cl)-CH(Br)-CH3
Tuesday, November 26, 2013 at 10:42pm

chemistry
A standard solution is prepared for the analysis of fluoxymesterone (C20H29FO3), an anabolic steroid. A stock solution is first prepared by dissolving 13.4 mg of fluoxymesterone in enough water to give a total volume of 500.0 mL. A 100.0-µL aliquot (portion) of this ...
Tuesday, November 26, 2013 at 10:42pm

CHEMISTRY
A chemist studying the equilibrium N2O4(g)<----->2NO2(g) controls the temperature so that keq ( equilibrium constant)= 0.028. At one equilibrium position, the concentration of N2O4 is 1.5 times greater than the concentration of NO2. Find the concentrations of the two ...
Tuesday, November 26, 2013 at 8:57pm

Chemistry
What are the individual orders of the reactants involved in the oxidation of methylene blue by ascorbic acid? Rate of reaction= [MB+]^m * [H2A]^n * [HCl]^p What are m, n, and p?
Tuesday, November 26, 2013 at 8:26pm

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 ...
Tuesday, November 26, 2013 at 8:16pm

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
Tuesday, November 26, 2013 at 7:55pm

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
Tuesday, November 26, 2013 at 7:52pm

Chemistry
At a certain temperature, the Kp for the decomposition of H2S is 0.774. H2S(g) <---> H2(g)+S(g) Initially, only H2S is present at a pressure of 0.120 atm in a closed container. What is the total pressure in the container at equilibrium?
Tuesday, November 26, 2013 at 6:22pm

chemistry
2. What is the percent yield of Mg3N2 if 73.9 g of Mg reacts with 31.6 g of N2 to produce 79 g of Mg3N2 according to the following chemical reaction? (Reaction may or may not be balanced.) mg+n2=Mg3N2
Tuesday, November 26, 2013 at 6:06pm

chemistry
what is the OH of a 0.025 M HF solution?
Tuesday, November 26, 2013 at 12:37pm

Chemistry
(a) Which of the following are requirements for anionic polymerization? 1-A double bond 2- End groups which can react by releasing a small molecule 3- A strong base to initiate the reaction 4- A strong acid to initiate the reaction 5- An electron-withdrawing group near the ...
Tuesday, November 26, 2013 at 11:57am

Chemistry
The surface tension versus log concentration for two surfactants is shown below. Describe in no more than five sentences how the two surfactants can be so different. You have only one attempt at this problem. People from Edx what is the answer for this question..I'm asking...
Tuesday, November 26, 2013 at 6:43am

Chemistry 12
Given the following [H3O+] or [OH-] and the concentration of the solution calculate the dissociation constant, Ka. [OH-] = 3.9 x 10^(-9) M, with a concentration of 0.50M Answer:1.3 x 10^(-11) How do I get this answer?
Tuesday, November 26, 2013 at 1:49am

chemistry
what is another way you could determine the enthalpy of formation of magnesium oxide beside the experimental method?
Monday, November 25, 2013 at 11:03pm

chemistry (Dr.Bob222)
Do serial dilutions start out as saturated solutions?, Meaning when it starts out ppt forms, but there is a point where ppt stops forming, so when the ppt stops forming does that mean it is representing a saturated solution, and that when the ppt is not forming the solution ...
Monday, November 25, 2013 at 10:40pm

Chemistry
H(f) Cl= 121.3 kj H(f) C= 716.7 H(f) CCl4= -95.7 calculate the average molar bond enthalpy of the carbon-chlorine bond in a CCl4 molecule. I have tried to figure it out and keep getting the wrong answer. Please help!
Monday, November 25, 2013 at 10:05pm

chemistry
predict the reaction, if any, that would occur if AgNo3 and KBr were mixed would any reaction occur if HBr was then added?
Monday, November 25, 2013 at 9:05pm

Chemistry
How much do 8.36 × 1022 molecules of water weigh? Answer in units of grams
Monday, November 25, 2013 at 8:43pm

Chemistry
What mass of rhodium contains as many atoms as there are zirconium atoms in 51 g of zirconium? Answer in units of grams.
Monday, November 25, 2013 at 8:41pm

Chemistry
Consider the reaction: CaCl2. 2H2O(s) <=> CaCl2(s) + 2H2O(g) The equilibrium constant for the reaction as written is
Monday, November 25, 2013 at 7:23pm

chemistry
When weighing liquid ethanol, why do you have to place water in the beaker prior to adding the ethanol to that same beaker? We were told to make a to make a 0.40% (wt/vol) stock solution by weighing 400 mg of absolute ethanol into a tared beaker that contained 15 mL of water ...
Monday, November 25, 2013 at 6:17pm

Chemistry
Please help! Is 4-methylphenol acid, basic or neutral?
Monday, November 25, 2013 at 5:24pm

Chemistry
1) A dog has the same mass for 3 years. State whether this represents an equilibrium or steady state situations, and give your reasons. I'm not sure if I got this question right... I think this is a steady state because the dog is opened to the environment where oxygen is ...
Monday, November 25, 2013 at 5:18pm

chemistry
Explain why is it important to have limiting reactant in stoichemestry?
Monday, November 25, 2013 at 2:56pm

chemistry
Why is limiting reactant important in stoichemestry?
Monday, November 25, 2013 at 2:33pm

Chemistry
What factors do you need to consider if you wish to use the volumetric method for preparation of stock ethanol solutions?
Sunday, November 24, 2013 at 6:45pm

Chemistry
When weighing liquid ethanol, why do you have to place water in the beaker prior to adding the ethanol to that same beaker?
Sunday, November 24, 2013 at 6:41pm

chemistry
Consider 15 mL of an aqueous solution containing 2.0 g of an organic solute. If the distribution coefficient for the solute between ether and water is 20, calculate the percent of the compound that can be recovered with a single extraction with 13.9 mL of ether
Sunday, November 24, 2013 at 5:49pm

Chemistry
Calculate the heat in kilojoules needed to condense 185g of steam at 100 ∘C.
Sunday, November 24, 2013 at 5:34pm

Chemistry
Calculate the heat in kilojoules needed to condense 185g of steam at 100 ∘C.
Sunday, November 24, 2013 at 5:33pm

Chemistry
A reaction: A(aq) + B(aq) <-> C(aq) has a standard free-energy change of –4.65 kJ/mol at 25 °C. What are the concentrations of A, B, and C at equilibrium if, at the beginning of the reaction, their concentrations are 0.30 M, 0.40 M, and 0 M, respectively? Im not...
Sunday, November 24, 2013 at 5:21pm

CHEMISTRY BALANCING CHEMICAL EQUATION
H2SO4 + NaOC = Na2SO4 + H2O
Saturday, November 23, 2013 at 7:11pm

Chemistry
Balancing Complete Redox Reactions I need help on the half reduction part for both reduction and oxidation of Cl2(g) --> cl^1- (aq) + OCl^1- (aq). I got both of the half reactions started. Cl2 --> Cl^- (Reduction) .... Cl^1- (aq) + OCl^1- (aq) (Oxidation). I need know ...
Saturday, November 23, 2013 at 11:53am

Chemistry
Balancing Complete Redxo Reactions. I am not sure how I am suppose to start anything. Even the Half Reactions. BrO3^1- + Br^1- + H^1+ --> Br2 + H20. I need to know all the steps on how to do half reactions & I think I should be good.
Saturday, November 23, 2013 at 11:53am

Chemistry
Balancing Complete Redox Reactions I need help on the half reduction part for both reduction and oxidation of Cl2(g) --> cl^1- (aq) + OCl^1- (aq). I got both of the half reactions started. Cl2 --> Cl^- (Reduction) .... Cl^1- (aq) + OCl^1- (aq) (Oxidation)
Saturday, November 23, 2013 at 11:50am

chemistry
20.0 g of ammonium nitrate (NH4NO3) is dissolved in 125 g of water in a coffee-cup calorimeter, the temperature falls from 296.5 K to 286.4 K. Find the value of q for the calorimeter.
Saturday, November 23, 2013 at 12:34am

Chemistry
In a double-stranded DNA molecule, the percentage of Guanine can never be more than ___%. Why?
Friday, November 22, 2013 at 2:51pm

Chemistry
What is the lattice energy of NaI? Use the given information below. Heat of formation for NaI = -288.0 kJ/mol Heat of sublimation for Na = 107.3 kJ/mol Ionization energy for Na = 496.0 kJ/mol Bond dissociation energy for I2 = 149 kJ/mol Electron affinity of I = -295.0 kJ/mol ...
Friday, November 22, 2013 at 1:05pm

chemistry
What are the values of [H3O+] and [OH−] for a solution with pH = 3.86?
Friday, November 22, 2013 at 11:43am

chemistry
Please I need help in knowing how to solve this. I know I need to take the antilog of something but don't know what.What is the values of [H3O+] for a solution with [OH−]=1×10−5M?
Friday, November 22, 2013 at 11:42am

Chemistry
Calculate the % composition of H2S. Then determine the number of grams of sulfur present in 339.79 g of H2S. *I don't know how to set up the equation after I find the % composition to find the grams of sulfur. Please help! Thanks, Bella :)
Friday, November 22, 2013 at 11:01am

chemistry
Calculate the % composition of H2S. Then determine the number of grams of sulfur present in 339.79 g of H2S. *I don't know how to set up the equation after I find the % composition to find the grams of sulfur. Please help! Thanks, Bella :)
Friday, November 22, 2013 at 11:00am

Chemistry
how many oxygen molecules are in 9.1 liters of oxygen gas?
Friday, November 22, 2013 at 10:57am

chemistry-Help
Glucose can be classified as an aldohexose. Name the following monosaccharide to indicate its carbonyl group and the number of carbon atoms. HO-CH2-C(=o)-C(H2O)-C(H2O)-CH2-OH
Friday, November 22, 2013 at 9:19am

Chemistry
In the titration of 20.00 mL of 0.175 M NaOH, calculate the number of milliliters of 0.200 M HCl that must be added to reach a pH of 12,55. I know the answer is 11,9 mL but I don't know how to calculate it.
Friday, November 22, 2013 at 6:04am

chemistry
Acids and Bases: What would be the pH of a solution made by adding 16.9 grams of hydrochloric acid to 2.50 L of water?
Friday, November 22, 2013 at 4:46am

chemistry
5.00×10−3mol of HBr are dissolved in water to make 15.0L of solution. What is the concentration of hydroxide ions, [OH−], in this solution?
Thursday, November 21, 2013 at 10:23pm

Chemistry
Which of the following statements must be True? Check all that apply. The number of Adenines in single-stranded DNA equals the number of Thymines. The number of Guanines in single-stranded DNA equals the number of Adenines. The number of Thymines in double-stranded DNA equals ...
Thursday, November 21, 2013 at 9:16pm

chemistry
if your lab partner determined that there were 4.030 x 1020 atoms of H in an unknown sample of C2H4Cl2, how many milligrams would the unknown sample weigh?
Thursday, November 21, 2013 at 7:23pm

chemistry
if your lab partner determined that there were 4.030 x 1020 atoms of H in an unknown sample of C2H4Cl2, how many milligrams would the unknown sample weigh?
Thursday, November 21, 2013 at 7:22pm

chemistry
if your lab partner determined that there were 4.030 x 1020 atoms of H in an unknown sample of C2H4Cl2, how many milligrams would the unknown sample weigh?
Thursday, November 21, 2013 at 7:22pm

Chemistry
Bromine has two naturally occurring isotopes. Bromine-79 has a mass of 78.918 amu (atomic mass unit) and is 50.69% abundant. Using the atomic mass reported on the periodic table, determine the mass of bromine-81, the other isotope of bromine.
Thursday, November 21, 2013 at 7:00pm

chemistry
I looked up how to solve it but my answer is coming out wrong. I don't know what i'm doing wrong please help!.Now if your lab partner determined that there were 4.030 x 1020 atoms of H in an unknown sample of C2H4Cl2, how many milligrams would the unknown sample weigh...
Thursday, November 21, 2013 at 6:45pm

chemistry
I looked up how to solve it but my answer is coming out wrong. I don't know what i'm doing wrong please help!.Now if your lab partner determined that there were 4.030 x 1020 atoms of H in an unknown sample of C2H4Cl2, how many milligrams would the unknown sample weigh...
Thursday, November 21, 2013 at 6:20pm

chemistry
I looked up how to solve it but my answer is coming out wrong. I don't know what i'm doing wrong please help!.Now if your lab partner determined that there were 4.030 x 1020 atoms of H in an unknown sample of C2H4Cl2, how many milligrams would the unknown sample weigh...
Thursday, November 21, 2013 at 6:18pm

chemistry
I looked up how to solve it but my answer is coming out wrong. I don't know what i'm doing wrong please help!.Now if your lab partner determined that there were 4.030 x 1020 atoms of H in an unknown sample of C2H4Cl2, how many milligrams would the unknown sample weigh...
Thursday, November 21, 2013 at 6:17pm

Chemistry
some of the acetic acid splashed out the beaker when you dropped the tablets into the acetic acid. How would this affect your measurement? Would your final calculated mass of sodium bicarbonate in the tablet be artificially high or low as a result of this splashing?
Thursday, November 21, 2013 at 5:58pm

Chemistry
How do you determine that a certain reagent will result in syn addition, anti addition, or be nonstereospecific? For instance the addition of H2/Pt to a cis-cyclic alkene results in a syn addition. HCl in water is nonstereospecific and Br2 in CCl4 is an anti addition. How can ...
Thursday, November 21, 2013 at 5:56pm

chemistry
Determine the mass of copper(ii)trioxonitrate(v) that will be formed,when 15g of copper is added to excess diluted trioxonitrate(v) acid. (cu=63.5, N=14, O=16)
Thursday, November 21, 2013 at 5:33pm

chemistry
Write the equation for the dissociation of carbonic acid.
Thursday, November 21, 2013 at 5:17pm

Chemistry
A 5.00g sample of octane is burned in a bomb calorimeter containing 200g of water. How much energy, in cal, is released if the water temperature increases 6.00C
Thursday, November 21, 2013 at 4:20pm

Chemistry
In certain first order reactions the concentration of the reactant decreases from 0.15 M to 0.11 M in 36 minutes . calculate the time of half reactions
Thursday, November 21, 2013 at 10:51am

chemistry(dr.bob22)
Glucose can be classified as an aldohexose. Name the following monosaccharide to indicate its carbonyl group and the number of carbon atoms. HO-CH2-C(=o)-C(H2O)-C(H2O)-CH2-OH
Thursday, November 21, 2013 at 9:00am

Chemistry
A student was given 100mL of HCL solution in a 250mL beaker and told that the HCL was 0.11M. The student was also given phenolphthalein indicator and 250 ML of 0.1234 M NaOH. The student first filled a buret with NaOH solution. The student then placed an appropriate volume of ...
Thursday, November 21, 2013 at 4:28am

chemistry
how do u hybridize for sulfate (SO4 -2)?
Thursday, November 21, 2013 at 3:52am

Chemistry
A helium atom has a smaller atomic radius than the hydrogen atom. Explain why.
Thursday, November 21, 2013 at 12:37am

Chemistry
Why does Cl- have a larger ionic radius than Ca2+ ?
Wednesday, November 20, 2013 at 11:58pm

Chemistry
Why does Cl- have a larger ionic radius than CA2+ ?
Wednesday, November 20, 2013 at 11:58pm

Chemistry
PLEASE HELP! I was just wondering why it is important to add an NaOH pellet to a nucleophile containing solution with ethanol before adding an electrophile.
Wednesday, November 20, 2013 at 11:49pm

Chemistry(Dr.Bob222)
What does it mean for something do to be neutralized? Is that when the [H+]=[OH-]? or is that totally wrong?
Wednesday, November 20, 2013 at 10:27pm

Modern Chemistry
Bromine has two naturally occurring isotopes. Bromine-79 has a mass of 78.918 amu and is 50.69% abundant. Using the atomic mass reported on the periodic table, determine the mass of bromine-81, the other isotope of bromine.
Wednesday, November 20, 2013 at 9:30pm

Chemistry
Rank the following in terms of increasing first ionization energy. 1. Na, Mg, N, O, F 2. F, N, O, Mg, N 3. F, O, N, Mg, Na 4. O, N, F, Na, Mg 5. Na, Mg, O, N, F
Wednesday, November 20, 2013 at 9:22pm

chemistry
consider the following reaction at 298K 4Al(s)+3O2(g) yields 2Al2O3(s) delta H= -3351.4 Kj find delta S sys find delta S surr find delta S unvi
Wednesday, November 20, 2013 at 9:10pm

Chemistry
calculate the minimum concentration of ag+ ion that must be added to (or built up in) a 0.140 m Na2CrO4 solution in order to initiate a precipitation of silver chromate. The ksp of ag2cro4 is 1.2 × 10^-12.
Wednesday, November 20, 2013 at 8:05pm

Chemistry
Sodium vapor lamps are often used in residential street lighting. They give off yellow light with a frequency of about 5.91 × 1014 Hz. What is this wavelength in nm?
Wednesday, November 20, 2013 at 7:25pm

Chemistry
how do i know which compounds to put the roman numeral in?
Wednesday, November 20, 2013 at 6:36pm

Organic Chemistry Help Please
We're going over the reactions involving Alkenes and Alkynes. However, I'm extremely confused I how to determine with solvent/solvents to use and also when already given the solvents with the reactants how this will effect the products. I studied the basic mechanisms ...
Wednesday, November 20, 2013 at 1:23pm

chemistry
Glucose can be classified as an aldohexose. Name the following monosaccharide to indicate its carbonyl group and the number of carbon atoms. HO-CH2-C(=o)-c(H2O)-C(H2O)-CH2-OH
Wednesday, November 20, 2013 at 10:38am

ANALYTICAL CHEMISTRY
A 24-h urine specimen was diluted to 2.000L and buffered to pH 10.0. A 10.00 mL aliquot was titrated with 27.32 mL of 0.003960 M EDTA. The calcium in a second 10.00 mL aliquot was iso;ated as solid CaC2O4, redissolved and titrated with 12.21 mL of the EDTA solution. a) ...
Wednesday, November 20, 2013 at 10:36am

Chemistry
Which of the following groups are indicative of anionic polymerization? a)F b)Cl c)COOCH3 d)H e)CH2CH3
Wednesday, November 20, 2013 at 3:57am

chemistry
Potassium metal, K, is more reactive than sodium, Na. Calcium, Ca, is less reactive than sodium. The comparative reactivity of these metals is K > Na > Ca. Explain the reactivity differences of K, Na and Ca based on their atomic structure.
Wednesday, November 20, 2013 at 1:28am

chemistry
First off, how do you eve find out if it would be colored or colorless? Will aqueous solutions of the following salts be colored or colorless? Explain. a. Titanium (II) chloride b. Beryllium chloride c. Tin (II) nitrate d. Iron (III) nitrate
Wednesday, November 20, 2013 at 1:28am

Chemistry
The most chemically reactive metal elements are the alkali metals. They react spontaneously with water or other substances in the atmosphere and must be stored under oil. a. What type of reactions will these metals undergo? b. Explain why these metals are so reactive in the ...
Tuesday, November 19, 2013 at 11:05pm

chemistry
The letters CHEMISTRY were spray painted in blue paint on the snow. After a while the sun comes out and the snow under the blue paint melts while the snow around the letters do not. Why did the snow under (rather than around) the blue paint melt?
Tuesday, November 19, 2013 at 11:05pm

Chemistry
Nitrate salts containing metal ions with the following electron configurations are added to water to make a solution. Predict whether the salt solution will be colored or colorless and explain the reasoning. a. [Kr]4d10 b. [Ar]3d3
Tuesday, November 19, 2013 at 11:04pm

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