1.)The silica that makes up the stationary phase in TLC chromatophraphy is more polar than the mobile phase. What then might the relative positions of the analgesics on the developed TLC plate tell you about the polarity of these molecules? Does this match the expectations ...
Monday, July 1, 2013 by Kris
The half-life for the second-order reaction of a substance A is 58.2 s when A0 = 0.63 mol L-1 Calculate the time needed for the concentration of A to decrease to the following values. (a) one-third of its original value (b) one-sixth of its original value (c) one-seventh of ...
Friday, June 28, 2013 by Sara
A researchr assistant made 160mg of a radioactive, and found that there was only 20mg left after 45hours. a) What is the half-life of this substance? b) Write a function to represent the amount of substance left after x hours c) If the researcher kew he needed 100mg of the ...
Sunday, June 23, 2013 by Kristen
A total charge of 96.5 kC is passed through an electrolytic cell. Determine the quantity of substance produced in each of the following cases. (a) the mass (in grams) of silver metal from a silver nitrate solution (b) the volume (in liters at 273 K and 1.00 atm) of chlorine ...
Friday, June 21, 2013 by Sara
Ok, so using Le Chatelier's Principle If you add heat to an exothermic reaction, the equilibrium will shift to the left. If you remove heat to an exothermic reaction, the equilibrium will shift to the right. What is it for an ENDOTHERMIC reaction? If you add a substance, ...
Tuesday, June 4, 2013 by K
find the molar enthalpy of vaporization for a substance, given that 3.21 mol of the substance absolve 28.4 kj of energy as heat when the substance changes from liquid to gas? show the work
Thursday, May 30, 2013 by ady
BaSO4(s)__><--- Ba2+(aq) + SO42−(aq) Adding what substance produces more SO4^2-??? This was a question, that had options of 1. SO4^2- 2. Ba2+ 3. BaSO4(s) 4. and i think a compound with NH in it Thank you
Wednesday, May 29, 2013 by Steve
TEACHER AIDE,CHILDREN, FAMILIES, SOCIETE
1. Larry is a very aggressive four-year-old child. He watches many television programs that contain violence. Its most likely that A. he will become overactive. C. his behavior wont change. B. he will become depressed. D. his behavior will become more aggressive. 2...
Saturday, May 18, 2013 by yani
A 14 gram sample of a substance that's used to preserve fruit and vegetables has a k-value of 0.1092. Find the substance's half-life, in days. Round your answer to the nearest tenth.
Tuesday, May 7, 2013 by Tristan
Please check my answers (at the bottom) with these questions. 1. An apple quickly changes color when exposed to air. This demonstrates a ________. (1 point) physical property chemical property physical change all of the above 2. When a chunk of dry ice is at room temperature, ...
Tuesday, May 7, 2013 by Annabelle Hartz
The quantity of heat that changes the temperature of a mass of a substance is given by , where is the specific heat capacity of the substance. For example, for , . And for a change of phase, the quantity of heat that changes the phase of a mass is , where is the heat of fusion...
Thursday, May 2, 2013 by Erica
I just to know how to identify the substance that is reduced, the substance that is oxidized, the oxidizing agent and the reducing agent in each reaction. As (s) + ClO3-(aq) → H3AsO3 (aq) + HClO(aq) CN-(aq) + MnO4-(aq) → CNO-(aq) + MnO2(s) C2H5OH + MnO4- → ...
Tuesday, April 30, 2013 by m
chemistry: please check answers.
1. How many valence electrons does a carbon atom have? A) 1 B) 2 C) 3 D) 4<<my answer 2. How many double covalent bonds are in an alkane? A) 0<<my answer B) 1 C) 2 D) 3 3. What is the general formula for a straight-chain alkane? A) CnHn B) CnHn+2 C) CnH2n D) CnH2n+...
Tuesday, April 30, 2013 by Anonymous
Pipette 3 drops of oil into a test tube of water and shake. Describe what takes place and why? - Would it be the oil settles at the top of the water, because the oil is less dense, and its a non-polar substance, so it doesn't mix with a polar substance (water). Add 1 scoop...
Tuesday, April 30, 2013 by K
Andrew measures they amount of a very unstable substance to be 100 moles. the half life of this substance is 3 days(after 3 days, half is gone). write an exponential function that models this situation where Y is the amount of substance and X is time in days. use your equation...
Friday, April 26, 2013 by Anonymous
During an experiment, you find that you can dissolve 3.6 g of a substance in 300 mL of water at 25°C. How much of the substance would you predict that you could dissolve in 600 mL of water at the same temperature? Can somebody help me with this? I don't get it.
Thursday, April 25, 2013 by Rebecca
Describe the life style disease/behaviour and explain 5 or more factors that contribute to the disease of substance abuse of both legal and illegal drugs among the youth
Thursday, April 25, 2013 by Selby
Objects A and B have the same mass of 3.4 kg and are at their melting points. They melt when 4.9 × 104 J of heat is added to A and when 11 × 104 J is added to B. (a), (b) Determine the latent heat of fusion for the substance from which each object is made. (c) Find...
Wednesday, April 24, 2013 by Anonymous
ELECTROLYSIS OF ZnI2
ELECTROLYSIS OF ZnI2 if you have done this experiment Please help me answer these questions as i missed the last half of my chem lab today. 1. What color change occurred when the wire is first heated. -next question is... What is the identity of the liberated metal? 2. what ...
Thursday, April 18, 2013 by sean
Grd 12 life orientation
Describe the life style behaviour and explain 5 factors that contribute to the substance abuse of both legal and illegal drugs among the youth
Wednesday, April 17, 2013 by Maupa Dimpho
What is the specific heat of an unknown substance if a 2.31 g sample releases 12.5 cal as its temperature changes from 24.9°C to 20.7°C? Please explain ans show steps.
Tuesday, April 16, 2013 by Julia
Substance X (MW=356gm) is a weak acid. Its Ka is 1.7x10^-3. Calculate pH of725ml of the following solutions: a)Containing 0.187 mol of substance x b)containing 127gm of Substance x I have been trying to figure this problem out for hours now and do not get it. Please help me ...
Tuesday, April 16, 2013 by Grace
Why is it difficult to distinguish between some pure substances and solutions? What methods can overcome this to define if either it is a pure substance or solution?
Sunday, April 14, 2013 by Sunny
AP CHEM HELP
When NH3 is added to solid Hg2Cl2, some of the mercury ions are oxidized and some are reduced. A reaction where the same substance is both oxidized and reduced is called a disproportionation reaction. Write equations for each of these half-reactions. HELP
Tuesday, April 9, 2013 by Colin
1. _____ is the process by which food is broken down so that nutrients can be used by the body. (1 point) Absorption Digestion Elimination Ingestion 2. What type of digestion takes place in the mouth? (1 point) chemical mechanical chemical and mechanical neither chemical nor ...
Monday, April 8, 2013 by Anonymous
H2C2O4.2H2O(s) is primary standard substance. 2.3688g of oxalic acid hydrate were completely neutralized by 42.56ml of NaOH solution. Calculate the molar concentration of the NaOH solution. Write the balanced equation for the reaction.
Monday, April 1, 2013 by Sean
7th Grade Sience
1. A person's belief that he or she needs a drug to feel good or function normally (1 point) addiction psychological dependence emphysema tolerance 2. A large, dome-shaped muscle below the lungs (1 point) trachea alveoli diaphragm emphysema 3. Smoke that is inhaled and ...
Thursday, March 28, 2013 by Anonymous
Eutrophication refers to 1. the concentration of a toxic substance in the tissues of organisms. 2. depletion of mineral resources as a result of leaching. 3. the warming of the earths surface. 4. the damage to the ozone layer that protects the earth from UV light. 5. ...
Tuesday, March 19, 2013 by Elena
assume that during the first 3 minutes after a foreign substance is introduced into the blood,the rate R'(t) at which new antibodies are produced(in thousands of antibodies per minute) is given by R'(t)=t/(t^2+1) where t is in minutes.find the total quantity of new ...
Tuesday, March 19, 2013 by tan
Plastic articles can be chromium-plated by coating them with thin layer of graphite paste,placing them in a bath of aqueous chromium(III) sulphate and electroplating. a)Suggest a reason why the article is first coated with graphite. b)what substance could be used for the other...
Sunday, March 10, 2013 by harish
Recall that all aqueoous solutions contain_____. Water can also undergo ____. This process is called the ______of water. The reaction can be written as: Notice the double arrow in the reaction. This indicates that the reaction is_____. However, only a tiny fraction of water ...
Thursday, March 7, 2013 by Kristien
These blanks I REALLLY need your help. Our teacher gave the teaching job to this other I think coop student who wants to be a teacher to teach for a day but I| seriously don't understand anything she said..in short I don't have anyyy clue about this. So please help me...
Thursday, March 7, 2013 by Kristien
Can someone check my answers please? I had specific trouble with 7, 13, and 27 (I'm pretty sure my other answers are correct; some reassurance would be nice though). And I have a small question about 8. 1. The ΔHf of an element in its standard state is defined to be 0...
Sunday, March 3, 2013 by a Canadian
A 1.065-g sample of an unknown substance is dissolved in 30.00 g of benzene; the freezing point of the solution is 4.25 degrees C. The compound is 50.69% C, 4.23% H, and 45.08% O by mass. Info you might need on benzene: Normal Freezing point,degrees C: 5.53 Kf, degrees m^1: 5....
Monday, February 25, 2013 by JJ
I need help in solving this problem: A certain substance has a heat of vaporization of 42.46 kJ/mol. At what Kelvin temperature will the vapor pressure be 5.00 times higher than it was at 291 K? I know that I have to use the Clausius-Clapeyron equation, but what would I be ...
Sunday, February 24, 2013 by Confused
sometimes,instead of percentage composition, you will have the composition of a mass sample. using the actual mass of the sample, determine the empirical formula for compounds that have the following analyses. b. a 13.07g sample of an unknown substance is composed of 9.48g of ...
Saturday, February 23, 2013 by tula
This is a chemistry lab report, but I was wondering if someone could edit the grammar and look at the sentence structure, etc. I know it's really long and boring, but even if you just look over a bit of it, I would really appreciate it. And I'm assuming you don't ...
Thursday, February 21, 2013 by a Canadian
"The heat engine uses 1.00x10^-2 mol of a diatomic gas as the working substance. Determine the temperatures at the 3 points." From 1-2, it's an adiabatic process and the constants are (P)(V^(7/5)) or (T)(V^(2/5)). From 2-3, it's an isobaric process with V/T ...
Thursday, February 21, 2013 by Summer
an unknown solid substance weighs 121g. calculate the specific heat if 425.2 cal raise the temperature of the solid from 24.0 degrees C to 55.7 degrees C.
Wednesday, February 20, 2013 by lila
Hi, here's my (almost) 2-paged lab report introduction (hopefully you remember it from yesterday). I went to class today, and actually a lot of my other classmates' introductions were over 2 pages! Now I'm feeling kind of insecure about mine, and I'm not even ...
Tuesday, February 19, 2013 by a Canadian
Calculate the net charge on a substance consisting of a combination of 7.5 multiplied by 1013 protons and 3.5 multiplied by 1013 electrons. Answer in units of C
Sunday, February 17, 2013 by Phil
A certain substance has a dielectric constant of 2.8 and a dielectric strength of 18.0 MV/m. If it is used as the dielectric material in a parallel-plate capacitor, what minimum area should the plates of the capacitor have to obtain a capacitance of 7.00×10-8 F and to ...
Thursday, February 14, 2013 by Nicole
Urgent Chem Help
A certain substance has a heat of vaporization of 55.30 kJ/mol. At what Kelvin temperature will the vapor pressure be 3.50 times higher than it was at 361 K?
Sunday, February 10, 2013 by Carl
A 6.9 gram sample of a gaseous substance occupies 10 L at 63C and 537 torr. What is the density of the gas under these conditions? Answer in units of g/L
Saturday, February 9, 2013 by cheri
7th grade health please help Ms. Sue!
1. Which substance found in tobacco is a drug that speeds up the heartbeat? (1 point) Tar Carbon monoxide Nicotine Emphysema 2. Which substance found in tobacco causes emphysema, a disease of the lungs? (1 point) Tar Carbon monoxide Nicotine Secondhand smoke 3. Which substance...
Wednesday, February 6, 2013 by Delilah
A mole of a pure substance contains 6.02x10^23 atoms. Alway true, sometime true or never true? -I was thinking sometime true since a pure substance can be like H2O but H2O have 3 "atoms" (Is this what you call individual part of H2O?). Each "atoms" have 6....
Tuesday, February 5, 2013 by Shadow
The decomposition of sulfuryl chloride (SO2Cl2) is a first-order process. The rate constant for the decomposition at 660 K is 4.5 10-2 s-1. (a) If we begin with an initial SO2Cl2 pressure of 425 torr, what is the pressure of this substance after 74 s? what is the equation to ...
Saturday, February 2, 2013 by Hannah
Rank the following species according to the decreasing energy needed to raise the temperature of 10.0g of the substance by 25.0 degrees celsius Rank from most to least energy needed. Rank these in order of the question. copper aluminum cast iron silver water
Friday, February 1, 2013 by mira
Why is the melting point of a known compound (ex. acetanilide) determined before the melting point of the unknown compound? I think it is to determine if the unknown is a pure substance but I am not sure..I just need to be pointed in the right direction.
Thursday, January 31, 2013 by Zach
An unknown substance has a volume of 25 mL. It is placed into a different container and its volume changes to 50 mL. What happened? Is it a change in state?
Tuesday, January 29, 2013 by Sebastian
The term mole is used in chemistry to define an amount of a substance. For example, a mole of glucose, blood sugar, weighs 180.16 grams. A common concentration unit for solutions is moles of substance per liter of solution. We abbreviate this with the symbol M. For example, 0....
Monday, January 28, 2013 by Ryan
The half life of a certain radioactive substance is 10 years. How long will it take for 18 gms of the substance to decay to 6 gms? A. 6 ln 10 years B. 10 ln 6 years C. 10 (ln 3)/(ln 6) years D. 18 ln 10 years E. 10 (ln 3)/(ln 2) years
Sunday, January 27, 2013 by Anonymous
1. Which one of the following is the most complete and accurate definition of fiber? A. A stringy substance from plants B. The hair of an animal C. Man-made threads and yarns D. Basic raw material from which fabric is made 2. An example of a natural fiber is A. nylon. B. ...
Friday, January 25, 2013 by caitlin
Light is incident from water onto a flat transparent slab of material, at an angle of 48.8° with the normal. The reflected ray and the refracted ray are perpendicular to each other. What is the index of refraction of the transparent substance?
Thursday, January 24, 2013 by Kiana