Monday
December 22, 2014

Posts by Annie


Total # Posts: 661

Chemistry
How would you usually prepare starch indicator solution for iodine titrations? Can the solution be stored for a few months in the fridge? I noticed that sometimes the starch indicator solution in the fridge has turned cloudy, in which case we should prepare a new solution?
September 25, 2010

physic
The angular position of a point on the rim of a 45.8 cm rotating wheel is given by θ(t) = 3.6 t2 − 2.8 t +7.5, What is the instantaneous speed v of the point at time t = 6.5 s?
September 20, 2010

Chemistry problem
I refer to my earlier post on v/v versus w/w. I would be very grateful for any advice provided. For 95% ethanol purchased from manufacturer, we normally take it as 95%v/v. For 98% sulphuric acid, it seems like it is normally 98% w/w. I have also seen a potassium hydroxide 85...
September 20, 2010

Chemistry - v/v versus w/w
Thanks a lot:) So just to confirm: normally for any chemical bought from manufacturer, if it is not stated, the % usually means v/v? Seems like for conc sulphuric acid, when it is stated 97% sulphuric acid, it means 97% w/w sulphuric acid? Thank you very much. Posted by annie ...
September 20, 2010

Chemistry -repost thank you in advance
I have a bottle of 95% ethanol purchased from the manufacturer. Normally, when it is not stated, does it mean 95% w/w ethanol? I need to prepare 100ml of 40% v/v ethanol solution from 95% ethanol. Please show me the calculation steps. Thanks.
September 20, 2010

Chemistry- urgent help needed
How do I prepare 40% v/v from 95% ethanol? When we say 95% ethanol, do we usually mean 95% w/w ethanol unless otherwise stated? Please show me the calculation steps to prepare 40% v/v from 95% w/w ethanol. Thanks.
September 19, 2010

Chemisty - urgent
Hi, how do I do the calculation? Thanks
September 15, 2010

Chemisty - urgent
How do I prepare 30% v/v ethanol from 95% ethanol? Thanks.
September 15, 2010

Chemistry
Sorry,please ignore my earlier post. Light sensitive materials are sampled in a room with yellow lighting. How is it different from normal white light?
September 14, 2010

chemistry
Light sensitive materials are samples under yellow lighting. Please explain what yellow lighting means.
September 14, 2010

history
what presidents make up mt rushmore
August 26, 2010

ecology
Explain atmospheric circulation and seasonal changes in the sun's orientation to earth to explain the highly seasonal rainfall in the tropical dry forest and tropical savanna biomes.
August 9, 2010

ecology
Why does the rainy season in the tropical dry forest and tropical savanna biomes come during the warmer months?
August 9, 2010

math
Oh wow, yes. you are right. That does make perfect sense! Sometimes I read to much into a problem. Thank you for simplifying for me Mrs. Sue. :)
July 30, 2010

math
yes, but .49 does not seem realistic. I may be doing something wrong. Thanks
July 30, 2010

math
Ok. I pretty much have this one solved but the final answer has me stumped. The probability that Luis will pass his statistics test is 0.51. Find the probability that he will fail his statistics test. This is what I have so far. P(fail)=.51; =1-.51. But I am not sure of the ...
July 30, 2010

Math
Yeah, I thought so just wasn't sure. Thank you!
July 30, 2010

Math
Ok. I have one more question. The mean height of 5 students is 59.4. If one of the students leaves, the mean height becomes 61. What is the height of the absent student? I have this so far but still having problems solving it: 5(59.4)=4(61)+1(X);X=? Thank you so much.
July 30, 2010

math/ algebra
ok, so my final answer is h=2, k=0, r^2=64, then r=8, is this right?
July 30, 2010

math/ algebra
Yup. That is what I got reiny. :) Thanks again.
July 30, 2010

math/ algebra
Thank you for your help! The question is what is the center and radius of the circle. (x+2)^2+y^2=64. Thank you so much.
July 30, 2010

math/linear equation
Yes, you are right! Thank you
July 30, 2010

chemistry
calculate the number of moles of carbon dioxide in a volume of 50.0 mL of carbon dioxide, assuming a pressure of 1.00 atm and a temperature of 23.0C
July 27, 2010

chemistry
dot and cross diagram of a molecule of HOCL
July 11, 2010

COLLEGE
IN A CLASS OF 100 57 STUDENTS RECEIVED A GRADE A WHAT FRACTION DID NOT RECEIVE AN A
June 4, 2010

Algebra
Evaluate a+b/10 for a=66 and b=4 a+b/10 = (simplify the answer)
May 26, 2010

math
Three pieces of wood are needed for a project. They are to be cut from a 90-cm-long piece of wood. The longest piece is to be 3 times as long as the middle-sized piece and the shortest piece is to be 10 cm shorter than the middle-sized piece. Can this be done with two cuts? If...
May 23, 2010

spanish
comer=to eat, tengo=have, yo=I
May 16, 2010

statistics
Bellevue Hospital in New York City uses 100.6 °F as the lowest temperature considered to indicate a fever. a. (0.1 point) What percentage of normal and healthy adults would be considered to have a fever? : b. (0.1 point) Does this percentage suggest that a cutoff of 100.6...
May 10, 2010

space
Will a lightbulb pop in space?
April 19, 2010

chemistry
A 1.00 L volume of helium gas is cooled from 50.0 degrees celcius to 25.0 degrees celcius. If the pressure remains constant, what is the final volume?
April 19, 2010

social studies
The religion of Islam (Muslums) and Christians are two different groups and cultures. Muslims are strict--can't speak to a woman until they they are engaged, yave to pary 5 times per day, women wear veils, marriages are arranaged, etc...women can't wear bathing suits...
April 16, 2010

6th grade
what is a word for what happens when you are confused?
April 15, 2010

math
If Titanic hit an iceberg at 11:40 p.m and 2 hours and 40 minutes later it sank, what time did it sink at?
April 14, 2010

social studies
What social classes existed in Aryan culture?
April 6, 2010

math
would (3x^4/15)^2 be x^8/25 when finally simplified?
February 24, 2010

math
if you had m^0g^0 would you leave it in that form or would the simplified version be 1?
February 22, 2010

mathy
if you had m^0g^0 would you leave it in that form or would the simplified version be 1?
February 22, 2010

math :(
Last year you mowed grass and shoveled snow for 10 households. You earned $200 per household mowing for the entire season & $180 per household for shoveling the entire season. If you earned a total of $1880 last year, how many households did you mow and shovel for?! How would ...
February 9, 2010

math
I totally understand now! i had the 2x+4y=100...i just was blanking out about how to set up the 2nd part but I see now! Thank you so much! :)
February 7, 2010

math
Your teacher is giving you a test worth 100 points containing 40 questions. There are two-point and four-point questions on the test. How many of each type of question are on the test? How would you set this up?
February 7, 2010

Math
Use systems of lineear equations to solve: An airplane flew for 6 hours with a 22-km/h tail wind. The return flight against the same wind took 8 hours. Find the speed of the plane in still air. I know the answer is 154 km/hr (back of book resources :) )...I just don't ...
February 4, 2010

physics
20(2090)(20+6)=1086800 J
January 27, 2010

Science
What is a bogus analysis using quasi-scientific jargon, but has little or no objectivity.
January 26, 2010

L.A.
is this a good beginning?!??! The movie, "Swing Kids", is not a light hearted, family film, but rather one that provokes deep emotions and thoughtful thinking within the viewer. This movie contains interesting information that shows the viewer how difficult it was ...
January 25, 2010

space
What is the force of gravity at 220 miles above Earth's surface? Calculate how much of a g force the astronauts are actually experiencing. The solution for this math problem is a percentage. You can calculate it using the Algebraic equation: gr = R2/r2 x g R = the radius ...
January 21, 2010

which of the folling values repesents an index of
which of the folling values represents an index of refraction of an actual material
January 11, 2010

Trig
How do you find csc 163degrees 20minutes? (I didn't know how to insert the degree and minute marks)
January 10, 2010

6th grae math
how can you add and multiplication at the same time
January 4, 2010

precalculus
convert the equation y^2 = 2x -x^2 into polar form. convert the equation r = 2tan(theta) into rectangular form. I'm not really sure what either of these mean. I vaguely understand polar coordinates, but I'm not sure how to convert equations back and forth between polar...
December 6, 2009

precalculus
Two people standing 30 feet apart look east at the top of a tree. The first person looks up at an angle of 78 degrees. The second person looks up at an angle of 62 degrees. How tall is the tree (to the nearest foot)?
December 6, 2009

Algebra
Sixty-two percent of the students at Kennedy High School are involved in extra curricular activities. If 152 students are not involved in extra curricualr activities, how many students are there at Kennedy High School?
November 18, 2009

math
thanks
November 15, 2009

math
i meant what is the mass of the block?
November 15, 2009

math
what is the density of the block? density is 2700 volume is 10^-4
November 15, 2009

math
sorry Ana... i missed typed it...again i apologize
November 15, 2009

Physics
i figured it out..thanks for helping me
November 15, 2009

Physics
A block of mass m1 = 4.80 kg sits on top of a second block of mass m2 = 15.6 kg, which in turn is on a horizontal table. The coefficients of friction between the two blocks are µs = 0.300 and µk = 0.100. The coefficients of friction between the lower block and the ...
October 31, 2009

Maths
Find the equation of the normal to the curve y = 3x^2 - 5x that is perpendicular to the line y = x + 4.
October 23, 2009

Com.
1.Assignment: Negative Messages Using templates or sample documents to help you write e-mails, memos, and letters may be helpful for inexperienced writers; however, customize the communication, so the document does not appear as a form letter. Use the information in your Week ...
October 18, 2009

physics
Hey thanks! At one point I was using (3/2)R(deltaT) but I wasn't setting it equal to (DeltaQ).
October 4, 2009

physics
We start with 5.00 moles of an ideal monatomic gas with an initial temperature of 123C. The gas expands and, in the process, absorbs an amount of heat equal to 1300J and does an amount of work equal to 2040J. What is the final temperature of the gas? Use R= 8.3145J/(mol*K) for...
October 4, 2009

6th grade
The lines of latitude divide the globe into units called what?
September 10, 2009

Geography
That was pretty quick! Thank you soo much! :D
September 8, 2009

Geography
What are the capitols of the following countries? 1. Spain 2. Mexico 3. Puerto Rico 4. Peru 5. Venezuela 6. Ecuador 7. Chile 8. Uraguay 9. Argentina 10. Cuba 11. Dominican Republic 12. Bolivia 13. Colombia 14. Paraguay 15. Panama 16. Nicaragua 17. Honduras 18. Guatemala 19. ...
September 8, 2009

Organic Chemistry
If biphenyl dissolves in both cold and hot methanol, would this be a good recrystallization solvent for biphenyl? Explain please!!!
August 26, 2009

English
In Great Expectations, what are the three spiritual stages that Pip goes through? What changes in Pip mark each progression into the next?
July 25, 2009

Chemistry
An ion exchange process may be used to remove ions causing hardness of water. Outline how this works. 1. Ca2+ and Mg2+ are the ions that cause the hardness of water, one example of softening the water is to react the hard water with NaCO3 (Sodium bicarbonate) to soften the ...
May 30, 2009

math
how would you solve: sin(2x)+cos(2x)=tan(x)?
May 28, 2009

physics loop
The small mass m sliding without friction along the looped track is to remain on the track at all times, even at the very top of the loop of radius r. (not unlike a roller coaster) A)In terms of the given quantities, determine the minimum release height h. (i got this to be 2....
May 22, 2009

physics
thanks! i used the two equations for w0 and set them equal to each other and solved for m and it worked! thanks!
May 22, 2009

physics imperfect spring
The force required to compress an imperfect horizontal spring an amount x is given by F= 150x+12x^3, where x is in meters and F in newtons. If the spring is compressed 2.1 m, what speed will it give to a 4.0 kg ball held against it and then released?
May 21, 2009

physics spring
the equation to use is more specifically x(t)=A(e^t*L)cos(w't) does that change it? because i'm still not getting the right answer
May 21, 2009

physics spring
but how do you find A (i'm assuming amplitude)?
May 21, 2009

physics spring
A glider on an air track is connected by springs to either end of the track. Both springs have the same spring constant,k , and the glider has mass M. A)Determine the frequency of the oscillation, assuming no damping, if k= 125N/m and M= 250g. (I got the answer to be 5.03 hz) ...
May 21, 2009

math
first, get them a common denominator (in this case 35). so (-8/7)5/5+(4/5)7/7= (-40/35)+(28/35) = (-40+28)/35 = -12/35 or so i believe
May 21, 2009

Math
take factors, beginning with the least common factors. ex: 90=3,3,10 two 3s (three squared) mean you take a three out, multiplying it by the square root of ten left.
May 21, 2009

math
would this be a correct proof of the cauchy-schwartz inequality: abs=absolute value abs(u*v) is less than or equal to abs(u)*abs(v). Then you divide both sides by abs(u)*abs(v) so that you get cos(theta) is less than or equal to 1.
May 14, 2009

Prealgebra
92% of 30 is what number
May 14, 2009

calculus
I am having alot of trouble remembering how to do this and this is a practice question for my final if you could help that would be great. Solve the differential equation (dy/dx)=(3x)/(1-x^2)
May 10, 2009

English 10 Cp
a question asked solely to produce an effect or to make an assertion and not to elicit a reply.
May 4, 2009

Chemistry
The addition of aqueous ammonia to the cathode compartment of the cell described below reduces the cell potential. Likewise, the addition of aqueous ammonia to the anode compartment increases the cell potential. Zn(s)/Zn^2+(aq)//Cu^2+/Cu(s) Assume that [Cu^2+(aq)]0=[Zn^2+(aq)]...
May 4, 2009

Chemistry
I understand this but i am confused becuase the problem uses a weak acid and strong base and the mLacid x Macid = mLbase x Mbase is for the equilibrium part put i am supposed to find the volume of titrant needed to reach the endpoint i think i am missing a concept. Please help
April 10, 2009

Chemistry
How do you calculate the volume of titrant needed to reach the endpoint of a reaction when you are given the mls and molarity of a strong base and only the molarity of a weak acid?
April 10, 2009

Latin
To translate the sentence, "I will not be the first to fight" is it "Non ero prima pugnare" or is it "non ero primum pugnare"... in other words, do I translate "I" as feminine because I am a girl, or do I translate it as neuter because ...
April 7, 2009

English
1) "I am filled with sadness." Can you explain the grammar rules for using "filled" instead of fill? 2)"We visited the Detainees (sic) camps and we saw the jails." What does '(sic)' mean? 3) Sometimes we see 'p.s.' at the end of a ...
April 2, 2009

Health
The body’s ongoing process of regulating its internal environment—electrolyte balance, blood chemistry, temperature, and so on—is called A. excretion. C. peristalsis. B. homeostasis. D. metabolism (B)
March 25, 2009

Health
An organelle is A. the smallest “living” structure in the body. B. a specialized body part composed of tissues. C. a structure in the cytoplasm. D. any complex living being, plant or animal. (c) is this correct
March 25, 2009

body systems
Thanks!
March 25, 2009

body systems
A 67-year-old man is diagnosed with cancer and subsequently undergoes chemotherapy. As an expected side effect of chemotherapy, his bone marrow stops functioning. What is a potential consequence of this loss of function? A. His calcium levels will decrease. B. He’ll ...
March 25, 2009

Science
When I bend down, what kind of force is involved? Is it the pulling force of the muscle?
February 16, 2009

Organic Chemistry
Jenn is correct. Rates of all reactions ( SN2, SN1, E1, and E2) increase if the leaving group has a better ability to part. The leaving group trend increases as you go down the periodic table of halogens.
January 21, 2009

chemistry
Thank you for the examples given. The teacher treats the gasoline explosion as low energy activation example because the gasoline only requires a spark to ignite. Do you agree it is a low energy activation example? By your example, I think that rusty nails is a high energy ...
January 17, 2009

chemistry
I need two real life examples of chemical reactions that require high activation energy. Please help.
January 17, 2009

chemistry
what does small electronegativity difference reveal about the strength of a covalent bond?
January 11, 2009

algebra
4-3x = x + 1
December 17, 2008

help plzzz
heyyy. im doing the same math sheet as well and is soooooo totally confused, lol
December 3, 2008

math
what is a boldface digit and how do you find its value
October 30, 2008

science
the density is the light wheight of an object . that winn help
October 30, 2008

history
draw one fighting the other anti and con.
October 30, 2008

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