What is Percent: Definition and 231 Discussions

In mathematics, a percentage (from Latin per centum "by a hundred") is a number or ratio expressed as a fraction of 100. It is often denoted using the percent sign, "%", although the abbreviations "pct.", "pct" and sometimes "pc" are also used. A percentage is a dimensionless number (pure number); it has no unit of measurement.

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  1. C

    Maximum Percent Recovery?

    One gram of salicylic acid dissolves in 460 mL of water at room temperature and 15 mL of boiling water. What is the maximum percent recovery that can be achieved using water as a recrystallization solvent assuming the recrystallization mixture is not cooled below room temp.? So I assumed we...
  2. H

    Percent by weight of substance in hydrate

    Q: Gypsum, used for wallboard, has the formula CaSO4 2H2O. (a) What is the percent by weight of water in this hydrate? (b) If 15.000 grams of this hydrate is heated, what mass of water would be lost? I'm thinking that I have to find out the mass of the CaSO4 and then the mass of 2H2O, then...
  3. K

    What is the percent abundance of 140Ce in Cerium?

    i am trying to figure out the percent abundance of two isotopes. i know how to set up the problem but i don't know how to find the weight of each isotopes. here is the problem: Cerium (58Ce) has two commonly occurring isotopes, 140Ce and 142Ce. what is the approximate percent abundance of 140Ce?
  4. Y

    Percent (by mass) composition

    % (by mass) composition Homework Statement Dopamine, C8 H11 O2 N is a neutroransmitter. Determine the percent (by mass) composition of each of the elements in dopamite.Homework Equations The Attempt at a Solution 8C atoms= 12 (12.0) = 44.0amu 11H atoms = 11 (1.0) = 11.0 amu 2O atoms = 2...
  5. F

    Calculating Percent Uncertainty in Area of a Circle

    I am asked "What is the area and it's approximate uncertainty of a circle of radius 3.8x10^4 cm?" Now finding the area is easy. In my text it says that when you aren't GIVEN an uncertainty, you can assume it is a reasonable figure in the last digit, so in this problem I am assuming the...
  6. W

    Molarity given percent solution and density.

    Homework Statement Lactose (C12H22O11; MM=342) is a sugar found in mamalian milk. The density of a 12.0% solution is approximately 1.06 g/mL. What is the molarity, molality, and mole fraction of the solution? Homework Equations M=g/L, m=mol/kg, molefraction=mol/mol?? The Attempt...
  7. G

    Percent Effect of variables in equation

    Anyidea on how to obtain the percentage or weight of each variable in an equation? for example: BBC = (X+1)*(a*b*c)/(U*V) what would each variable X,a,b,c,U,V weight in percentage in equation BBC? Appreciate it.
  8. S

    Weight percent and concentration problem

    the question is at below. 320ml of 29wt% of ammonium hydroxide 1210ml of 31wt% of hydrogen peroxide 30190ml of water mixed together. What is the concentration of ammonium hydroxide and hydrogen peroxide now? Is there any reaction occurs between them?
  9. G

    Percent Uncertainty in Spherical Beach Ball Volume

    Homework Statement What, roughly, is the percent uncertainty in the volume of a spherical beach ball whose radius is r = 0.84 + or - 0.06m? Answer must have 2 sig figs. Homework Equations The Attempt at a Solution I found the volume of the sphere with .84 radius which would be 3.0 m^3 and...
  10. A

    Calculating Percent Yield: K2PtCl4 + 2 NH3 -> Pt(NH3)2Cl2 + 2 KCl

    Homework Statement Given the following equation: K2PtCl4 + 2 NH3 -----> Pt(NH3)2Cl2 + 2 KCl c) Starting with 34.5 g of NH3, and you isolate 76.4 g of Pt(NH3)2Cl2, what is the percent yield? The Attempt at a Solution I had to balance the eqn, which was pretty easy. Then I determined...
  11. M

    Ice Floats: Calculating Water Level Percent

    Homework Statement If ice floats in water, how many percent of it show above the water level? density of water=1000kg/m^3 density of ice=920kg/m^3Homework Equations I really don't know how to start and what I have to do with those densities...just give me a hint. solution would be 8%
  12. S

    Percent Uncertainty Problem -NEED HELP

    Percent Uncertainty Problem -NEED URGENT HELP! Homework Statement The question is: What, approximately, is the percent uncertainty for the measurement given as 1.57 m^2. Homework Equations I know the formula that this textbook: 6th edition: Physics - Giancoli gave. It is simply, the...
  13. 6

    Calculate the Percent Composition of an Herbicide from Analysis Data?

    Homework Statement An herbicide is found to contain only C, H, N, and Cl. The complete combustion of a 100.0-mg sample of the herbicide in excess oxygen produces 83.16 mL of CO2 and 73.30 mL of H2O vapor at STP. A separate analysis shows that the sample also contains 16.44 mg of Cl...
  14. S

    Materials Question - Calculating Percent Carbon ?

    Homework Statement Calculate the percent carbon in an iron-carbon alloy that will give no volume change when liquid transforms to austenite plus graphite during solidification. Homework Equations Density of liquid = 7.0 g/cc Density of austenite = 7.69 g/cc Density of graphite = 1.5...
  15. L

    How can the energy absorbed by the water be more than the energy output?

    Homework Statement The heating element in a kettle has a resistance of 10 ohms when it is plugged into a 110V outlet. When heating water, only 75% of the energy produced is actually absorbed by the water. How much heat energy does the water absorb if it takes 4 minutes to boil the water...
  16. C

    Theoretical Yield, Molar Mass, and Percent Yield

    Hi, I have a few questions that I am struggling with. Any help would be greatly appreciated. Question 1 Calculate the molar mass of calcium chloride dihydrate, CaCl2 • 2H2O. Please use the Periodic Table values rounded to the hundredths place for your calculation and round your answer to...
  17. Phrak

    Percent% Errror Quoted for Electrical Components. What is it?

    Errror Quoted for Electrical Components. What is it? (Where do I post electrical engineering homework questions? I'm home. I'm working. OK, maybe I'm not really working.) Manufacturers quote a percent variation from nominal value for their parts. What does this percent error even mean...
  18. R

    Calculating the composition of vapor in mass percent

    Homework Statement Here's the question form the text. (I have the answer, but don't know how to do part c. "A solution contains 50.0g of heptane (C7H16) and 50.0g of octane (C8H18) at 25 C. the vapor pressures of pure heptane and pure octane at 25 C are 45.8 torr and 10.9 torr...
  19. Q

    Percent Length Contraction (check solution)

    Question: What is the percent length contraction of an aircraft traveling at Mach 2? So, we know that Mach 2= 680.58 m/s and that L'=L\sqrt{1-(v/c)^2} If you divide over the L to get: L'/L=\sqrt{1-(v/c)^2}=% length contraction Plug-n-chug from here to get...
  20. P

    What is the Volume Occupied by Saturated Water Vapor in a Rigid Container?

    Homework Statement A rigid container of volume 1 m^3 contains saturated water at 1MPa. If the quality is .10, what is the volume occupied by the vapor. Homework Equations The Attempt at a Solution I wanted to use the equation v=(1-x)(v_l)+x(v_v) where all v's are specific...
  21. K

    Finding the percent weight an element in an Alloy

    Homework Statement Determine the wt% of lithium required to obtain an Al-Li alloy with a density of 2.55 g/cm^3. Homework Equations The Attempt at a Solution I am so lost in this problem, any hints of how to start this problem with GREATLY appreciated!
  22. B

    Percent by mass concentration

    % by mass concentration Homework Statement An aqueous CaCL2 solution has a vapor pressure of 80.8mmHG at 50 degree C . The vapor pressure of pure water at this temperature is 92.6 mmHG . What is the concentration of CaCl2 in mass percent? Homework Equations % by mass = mass solute/mass...
  23. 3

    Find Percent Composition of Ethylene from Natural Gas Sample

    Homework Statement A 5.00g sample of natural gas, containing methane, CH4, and ethylene, C2H4, was burned in excess oxygen, yielding 14.5g CO2 and some H2O as products. What percent of the sample was ethylene? Homework Equations Moles and percent composition The Attempt at a...
  24. P

    Percent at. concentration unit?

    % at. concentration unit? hi all i wonder if someone can help me to know about the concentration measurement unit (% at. ), what does that mean?? thanks
  25. V

    Having to do with standard deviation, and percent of scores. Please help me.

    Homework Statement The scores on an exam are normally distributed, with a mean of 77 and a standard deviation of 5. What percent of the scores are greater than 87? Homework Equations The Attempt at a Solution I don't understand what it is exactly that I have to do to get the...
  26. P

    Weight percent of element to give specific density for alloy

    Homework Statement Aluminium-Lithium alloys have been developed by the aircraft industry to reduce the weight and improve the performance of its aircraft. A commercial aircraft skin material having a density of 2.47 g/cm3 is desired. Compute the concentration of Li (in wt%) that is required...
  27. P

    Weight percent of Ge needed to yield alloy with x atoms/cm3

    Homework Statement Germanium forms a substitutional solid solution with silicon. Compute the weight percent of germanium that must be added to silicon to yield an alloy that contains 2.43e21 Ge atoms per cubic centimeter. The densities of pure Ge and Si are 5.32 and 2.33 g/cm3 respectively...
  28. C

    What is the device used to measure percent light absorption in pigments?

    What is the device used to measure percent light absorption in pigments? I remember finding the percent light absorption in the pigments of some vegetables for a high school bio lab. I am pretty sure the device used was not specific for pigments. The device was user friendly- we just stuck...
  29. S

    Recrystallization Percent Recovery

    Homework Statement Calculating percent recovery of an unknown solid and describing if the percent recovery represents the "true" value of the recovered pure solid. How do we know that quality of an unknown solid which was recrystallized improved as a result of the recrystallization...
  30. C

    Thermal expansion, percent change in density problem

    Homework Statement When the temperature of a metal cylinder is raised from 0.0°C to 100°C, its length increases by 0.23%. Find the percent change in density. Homework Equations ∆L = L∆T p=m/v The Attempt at a Solution I don't have any real idea how to start the problem. How...
  31. J

    Calculating Volume of Acetone for Solution with Methylene Chloride

    Homework Statement What volume (L) of the solvent acetone should be added to 1790 g of the solute methylene chloride to make a solution that is 20.3 g methylene chloride per 100. g solution? Molar Mass (g/mol) CH2Cl2 84.93 (CH3)2CO 58.05 Density (g/mL): CH2Cl2 1.327 (CH3)2CO...
  32. T

    Easy percent composition question

    1. For a problem I require the atomic density of uranium atoms per cm^3 in a solution of water. The atomic fraction of natural uranium to water is 1 per 100 and the net density of the solution is 1 g/cm^3. (Natural uranium is assumed to be U-235 at 0.72% of uranium atoms and the rest is U-238)...
  33. S

    Percent of sodium oxalate help

    I have been suck on a problem for days: We dissolve 3.778g of a sample that contains some sodium oxalate, Na_2C_2O_4, in water and acidify the solution with excess sulfuic acid. The sample requires 18.74 mL of 0.08395 M KMnO_4, potassium permanganate, for complete reaction according to the...
  34. M

    Calculating Glucose Concentration of Solution

    [SOLVED] Percent of solution Homework Statement Let's say we have 5% glucose of a 10 mL solution. So that would imply that .5 mL of the solution is glucose, but that does not really tell me how much glucose. Is it assumed that the glucose is 1 molar? I ask because in one of my bio...
  35. I

    Chemistry Calculating Percent Yield in Moles: Is It Different?

    Is calculating the percent yield in moles different than calculating the percent yield in mass? I know that to calculate the percent yield in mass, you divide the actual over the theoretical and multiply by 100. There happens to be a side note in my homework saying that percent yiled can...
  36. L

    Percent Composition and Finding Formula - Chemistry

    % Composition and Finding Formula - Chemistry 50.0g of Sulphur is mixed with 100.0g of iron and heated strongly. When the reaction is complete 12.5g of iron remains. What is the formula of the sulphide formed? What i have done so far is i got the 2 mols of each element. Fe=1.79 S=1.56...
  37. L

    Percent Composition & Finding Formula - Chemistry

    % Composition & Finding Formula - Chemistry 50.0g of Sulphur is mixed with 100.0g of iron and heated strongly. When the reaction is complete 12.5g of iron remains. What is the formula of sulphide formed? duno where to start
  38. C

    Percent hydrolysis/percent ionazation

    Im just wondering if percent hydrolysis and percent ionization are the same thing? Thanks!
  39. D

    Percent uncertainty of momentum

    Homework Statement The position and momentum of a 1KeV electron are simultaneously determined. If its position is located to within 1Angstrom (Δx), what is the PERCENTAGE of uncertainty in its momentum?Homework Equations ΔxΔp >= h(bar)/2The Attempt at a Solution Δx = 1A = 1x10^-10m Δp>=...
  40. K

    Osmotic Pressure & Mass Percent

    [SOLVED] Osmotic Pressure & Mass Percent A solid mixture of KCL, KNO3, and Ba(NO3)2 is 20.92 mass percent chlorine, and a 1.000g sample of the mixture in 500.0 mL of aqueous solution at 25 C has an osmotic pressure of 744.7 mm Hg. What are the mass percents of KCl, KNO3, and Ba(NO3)2 in...
  41. K

    Ammonium hydroxide Percent to normality conversion

    Hi all, I was trying to make a 0.3N ammonium hydroxide solution from the stock (Fluka). The label on the stock says it is "10% assay in water", what does it mean? Is it 10% v/v? How should I prepare a 1ml 0.3N ammonium hydroxide? I don't quite understand the solute mass equivalent concept of...
  42. W

    Calculating Percent Error When Accepted Value is 0

    how do you find the percent error when the accepted value is 0? you would be dividing by 0 and that just doesn't work
  43. G

    Percent efficiency of three power generators

    A coal power plant with three power generators is used to power a small city. If each generator uses 1.22 X 10^8 J of chemical energy in the coal every hour, and the average annual energy consumption of the city is 1.61 X 10^12 J. What is the efficiency of the generators? (Assume the...
  44. G

    What does it mean to determine the precision, expressed as percent

    In my lab class, I needed to find k for a spring in two ways (hanging a mass from a spring & through simple harmonic motion). I've done this and now need to compare the two values - the question asks me to determine "the precision, expressed as a percent" of my measurements for k - I don't...
  45. J

    How to Calculate Percent Error in Measurements: A Guide

    How does one calculate percent error in measurements? In attempting to measure a distance of some centimeters with a meter stick, how could I estimate it? Isn't a meter stick accurate to the millimeter?
  46. G

    Using Differentials to find Error and Percent Error

    Homework Statement One side of a right triangle is known to be 20 cm long and the opposite angle is measured as 30(degrees), with a possible error of +/- 1 degree. a) Use differentials to estimate the error in computing the length of the hypotenuse b) what is the percentage error...
  47. H

    Calculating Percent Mn in Sample with Mn2(SO4)3 and Al2(SO4)3

    A 5.62-g sample containing only Mn2(SO4)3(s) and Al2(SO4)3(s) is dissolved in aqueous solution. The metal ions are precipitated as hydroxides, which are pyrolyzed in air to produce 2.06 g of a mixture of Mn2O3(s) and Al2O3(s). What was the percent Mn in the original sample? what i did so...
  48. P

    What is the Percent of Salt by Weight in Mono Lake at Different Water Levels?

    High School Geometry Homework Statement When the concentration of salt in a lake is greater than three percent by weight, the lake is a salt lake. Find the percent of salt by weight for each of the water levels of Mono Lake Shown in the table. One liter of water weighs 1kg or 1000 grams...
  49. E

    What percent of baryonic matter is antimatter?

    What percent of baryonic matter is antimatter? I am well aware that DM accounts for most "matter" and that there was baryon number violation and cp violation to explain the presence of matter over antimatter, but based on theory and observation, what percent of visible matter is predicted or...
  50. T

    Understanding Percent Increase: 2184 is 9.2% Larger than 2000

    Homework Statement How much larger than 2000 is 2184 in percent? 2. The attempt at a solution I'm struggling with understanding what figure should be divided by the other. If I do 2000/2184*100 I get 91.6, obviously not the right answer. If I do 2184/2000*100 I get 109.2, leading me...
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