# Posts by SARA

Total # Posts: 4,465

**Chemistry**

A couple questions here: 1. How do you expect nitriding to change the properties of iron? a) Nitriding makes iron stronger. b) Nitriding makes iron weaker. c) Nitriding makes iron more electrically conductive. d) Nitriding makes iron less electrically conductive. 2. Calculate ...

*July 10, 2013*

**business communication**

would you please rephrase it? my boss has given me to rewrite it for international employees. i want it to have in simple english so that every body can understand

*July 10, 2013*

**business communication**

can you plz correct it Howdy comrades! Shouldn’t surprise anyone that we took a beating this year, given the insane pricing moves our knucklehead competitors have been making. I mean how those clowns can keep turning a profit is beyond me, what with steel costs still ...

*July 10, 2013*

**mathematics**

(5,400) the actual value of y-the predicted value 400-471.44=-71.44 big difference between the actual value and predicted value of y therefore the regression equation is not very reliable.

*July 9, 2013*

**Calculus-HELP!!!**

Find a general solution to the first – degree ordinary differential equation. If an initial condition is given, find the corresponding particular solution. Write solution explicitly if possible: dx/dt=sqrt(x+t+1)

*July 8, 2013*

**Calculus-HELP PLZ !!!!**

Find a general solution to the first – degree ODE. If an initial condition is given, find the corresponding particular solution. Write solution explicitly if possible. (9x^2+y-1)dx-(4y-x)dy=0, y(1)=0

*July 7, 2013*

**Calculus**

Find a general solution to each first – degree ODE. If an initial condition is given, find the corresponding particular solution. Write all solutions explicitly if possible. dr/dè = r^(2)/è

*July 5, 2013*

**Calculus**

Show that both functions y1=e^(-2x) and y2=xe^(-2x) are solutions to the differential equation y^''+4y^'+4y=0

*July 2, 2013*

**Statistics**

A company has developed a new type of light bulb, and wants to estimate its mean lifetime. A simple random sample of 12 bulbs had a sample mean lifetime of 692 hours with a sample standard deviation of 30 hours. It is reasonable to believe that the population is approximately ...

*July 1, 2013*

**physics**

a) μ = Fc/FN (i) FN =(950x9.8)+12000= 21310 Fc =(950)(46)^2/120= 16751 Putting values in (i) μ=0.7860 (no unit) b) v= sqrt(rμg)= sqrt[(120)(0.7860)(9.8)] v= 30.40 m/s^2

*July 1, 2013*

**Chemistry**

Dinitrogen pentoxide, N2O5, decomposes by first-order kinetics with a rate constant of 0.15 s-1 at 353 K. (a) What is the half-life (in seconds) for the decomposition of N2O5 at 353 K? (b) If [N2O5]0 = 0.0579 mol·L-1, what will be the concentration of N2O5 after 4.0 s...

*June 28, 2013*

**Chemistry**

a) 2A --> B + C b) 2A --> B + C c) 2A --> 3B + C

*June 28, 2013*

**Chemistry**

Determine the rate constant for each of the following first-order reactions. In each case, write the rate law for the rate of loss of A. (a) 2 A B + C, given that the concentration of A decreases to one-fourth its initial value in 57 min (b) 2 A B + C, given that A0 = 0.036 ...

*June 28, 2013*

**Chemistry**

The presence of a catalyst provides a reaction pathway in which the activation energy of a certain reaction is reduced from 125 kJ·mol-1 to 75 kJ·mol-1. (a) By what factor does the rate of the reaction increase at 293 K, all other factors being equal? (b) By what...

*June 28, 2013*

**Chemistry**

Ethane, C2H6, forms ·CH3 radicals at 700.°C in a first-order reaction, for which k = 1.98 h-1. (a) What is the half-life for the reaction? (b) Calculate the time needed for the amount of ethane to fall from 1.00 10-3 mol to 2.48 10-4 mol in a 500. mL reaction vessel...

*June 28, 2013*

**Chemistry**

When 0.13 g of H2 and 0.18 g of I2 are confined to a 150. mL reaction vessel and heated to 700. K, they react by a second-order process (first order in each reactant), with k = 0.063 L·mol-1s-1 in the rate law (for the rate of formation of HI). (a) What is the initial ...

*June 28, 2013*

**Chemistry**

Dinitrogen pentoxide, N2O5, decomposes by a first-order reaction. What is the initial rate of decomposition of N2O5 when 3.6 g of N2O5 is confined in a 0.77 L container and heated to 65°C? For this reaction, k = 5.2 x 10^-3 s-1 in the rate law (for the rate of ...

*June 28, 2013*

**Chemistry**

Dinitrogen pentoxide, N2O5, decomposes by first-order kinetics with a rate constant of 0.15 s-1 at 353 K. (a) What is the half-life (in seconds) for the decomposition of N2O5 at 353 K? (b) If [N2O5]0 = 0.0579 mol·L-1, what will be the concentration of N2O5 after 4.0 s...

*June 28, 2013*

**Chemistry**

a) 2A --> B + 2C b) A --> C + 2D

*June 28, 2013*

**Chemistry**

Determine the rate constant for each of the following second-order reactions. In each case, express your results in terms of the rate law for the loss of A. (a) 2 A B + 2 C, given that the concentration of A decreases from 2.74 mmol·L-1 to 1.46 mmol·L-1 in 122 s...

*June 28, 2013*

**Chemistry**

I understand, but what is K or how can I determine K?

*June 28, 2013*

**Chemistry**

I don't understand how to figure out K. I used the information in the problem given to solve for k, and then plug that k in to solve for t, but it's not the correct answer.

*June 28, 2013*

**Chemistry**

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 ...

*June 28, 2013*

**Chemistry**

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 ...

*June 21, 2013*

**Chemistry**

Predict the standard emf of each of the following galvanic cells. (a) Sn(s)|Sn2+(aq)||Sn4+(aq),Sn2+(aq)|Pt(s) (b) Pt(s)|Fe3+(aq),Fe2+(aq)||Ag+(aq)|Ag(s) I don't want the answer, I want the procedure/methods of how to do these types of problems.

*June 21, 2013*

**Chemistry**

Balance the reaction of plumbate ions and hydrochlorite ions: Pb(OH)42-(aq) + ClO-(aq) → PbO2(s) + Cl- I put: Pb(OH)3-(aq) + ClO-(aq) → PbO2(s) + Cl-(aq) + H2O(l) + OH-(aq) It said: The reaction described in your answer is not balanced. One or more of your ...

*June 21, 2013*

**Chemistry**

Reaction of hydrazine with chlorate ions N2H4(g) + ClO3-(aq) → NO(g) + Cl-(aq) Balanced: 3N2H4(g) + 4ClO3-(aq) → 6NO(g) + 6H2O(l) + 4Cl-(aq) Reducing agent: ClO3- Oxidizing agent: N2H4 Right?

*June 21, 2013*

**Chemistry**

Either my online portal hates me, or I don't understand how to balance properly. QUESTION Balance reaction of arsenic(III) sulfide with nitric acid As2S3(s) + NO3-(aq) → H3AsO4(aq) + S(s) + NO(g) Is this the correct balanced equation? 32 H2O + 24 As2S3(s) + 80 H+(aq...

*June 21, 2013*

**Chemistry**

Sorry, for the oxidizing, I put this: Fe^2+

*June 21, 2013*

**Chemistry**

Balance each of the following skeletal equations by using oxidation and reduction half reactions. All the reactions take place in acidic solution. Identify the oxidizing agent and reducing agent in each reaction. (Use the lowest possible coefficients. Include states-of-matter ...

*June 21, 2013*

**Physics (trig)**

The height of an outdoor basketball backboard is 12 1/3 feet and the backboard casts a shadow 19 1/5 feet. Find the angle of elevation of the sun (answer in units of degrees). Can someone help me with the formula? Thank you!

*June 19, 2013*

**Physics (algebra)**

the sonar of a navy cruiser detects a submarine that is d=4601 ft from the cruiser. the angle between the water level and the submarine is 0=32 degrees. What formula should I use to solve?

*June 18, 2013*

**maths**

a sum of money trebles in 9years 4 months.in how many years will it double

*June 15, 2013*

**Chemistry**

The pH of 0.40 M HF(aq) is 1.93. Calculate the change in pH when 0.301 g of sodium fluoride is added to 53.7 mL of the solution. Ignore any change in volume.

*June 14, 2013*

**chemistry**

Suppose that 0.483 g of an unknown monoprotic weak acid, HA, is dissolved in water. Titration of the solution with 0.250 M NaOH(aq) required 42.0 mL to reach the stoichiometric point. After the addition of 21.0 mL, the pH of the solution was found to be 3.75. (a) What is the ...

*June 14, 2013*

**Chemistry**

moles of H2SO3 = 0.0246 moles of 2NaOH = 0.04925 Second stiochiometric point volume: 400. mL First stiochiometric point volume: 200. mL Thanks!

*June 14, 2013*

**Chemistry**

What volume of 0.123 M NaOH(aq) must be added to 125 mL of 0.197 M H2SO3(aq) to reach the following points? (a) the first stoichiometric point (b) the second stoichiometric point

*June 14, 2013*

**Chemistry**

What volume of 0.123 M NaOH(aq) must be added to 125 mL of 0.197 M H2SO3(aq) to reach the following points? (a) the first stoichiometric point (b) the second stoichiometric point

*June 14, 2013*

**CALCULUS**

Find the gradient and directional derivative of f at P in the direction of v: f(x,y)=ln(x^2 + y^2 +1)+ e^(2xy) P(0,2) v=5i-12j

*June 2, 2013*

**Calculus - HELP plz!**

Find all of the first partial derivatives of f(x,y,z)=arctan y/xz

*June 2, 2013*

**vectors**

why are the answers in the back of my textbook,[3,4,-1], [4,5,-5], [2,3,3]

*May 27, 2013*

**vectors**

find three points on each plane [x,y,z]= [3,4,-1]+s[1,1,-4]+ t[2,-5,3]

*May 27, 2013*

**physics**

a horizontal force of 600Npulls two masses 10kg lying on a frictionnnnless surface connected by a light string .what is the tension in the string?Does the answer depend on which mass end the pull is applied

*May 26, 2013*

**physics**

explai biot-savart,law.an electron with velocity 3*107ms1 describe a circular path in a uniform magnetic field of 0.2T,perpendicular to it.calculate the radius of path

*May 23, 2013*

**math**

at a certain factory each worker either drives to work or take the bus. the ratio of worker who take the bus to those who drive to work is 2:5. if 120 worker drive to work how many workers are there at the factory?

*May 16, 2013*

**Physical Science**

my dear , how did you get this formula of KE, KE=mv2/2 and the mass is equal to (rho)(volume ) so KE=(RHO)(VOLUME)(V2)/2 ,, I confused , can you explain more please

*May 13, 2013*

**Physical Science**

Thank you

*May 13, 2013*

**Physical Science**

- What is the kinetic energy ,KE, per unit volume V of blood that has a speed of 0.5 m/s. Take density ofƒâblood = 1.0x103kg/m3

*May 13, 2013*

**Microbiology**

How can lab practices and safety precautions help reduce hazards in a lab setting? How do you handle blood cultures and pathogenic strains in a lab to minimize contamination?

*May 3, 2013*

**maths**

Consider the following system of inequalities: {(c−1)x^2+2cx+c+4≤0 cx^2+2(c+1)x+(c+1)≥0 The sum of all real values of c, such that the system has a unique solution, can be written as ab, where a and b are coprime positive integers. What is the value of a+b? ...

*May 3, 2013*

**statistics**

the probability that a house in an urban area will develop a leak is 5%. if 23 houses are randomly selected, what is the probability that none of the houses will develop a leak?

*April 28, 2013*

**Chemistry**

What is the pH of a solution of 40.0 ml of 0.800 M HCl titrated with 4.00 ml of 1.00 M Hydroxyl amine?

*April 24, 2013*

**Physics :(( help please TT**

thanxxxxxxx hero.........

*April 23, 2013*

**chemistry**

how many gram of h2 needed to react with 3.10 n2

*April 18, 2013*

**chemistry**

how many gram of h2 needed to react with 3.10 n2

*April 18, 2013*

**PHYSICS**

The only force acting on a particle is conservative force F. If the particle is at point A, the potential energy of the system associated with F and the particle is 39 J. If the particle moves from point A to point B, the work done on the particle by F is +25 J. What is the ...

*April 17, 2013*

**CALCULUS-plz help!**

For the curve r = 2 sin 3(theta): Find the arc length of one petal

*April 16, 2013*

**CALCULUS-plz help!**

For the curve r = 2 sin 3(theta): Find the arc length of one petal

*April 16, 2013*

**Math**

I think I figure it out. The answer is: 12 A ^2 * 2 A * - 31 + 4 A * 6 + / I figured that that the square sign and the number 2 count as one operator. For ^2 I just use the x^2 button on the calculator and it gave me the same answers.

*April 15, 2013*

**Math**

I need to change this expression to postfix form. (12*A^2-2*A+31)/(4*A+6) I know how to do this except for the squaring part. I got stuck. This is my try. 12 A 2 ^ * 2 A * - 31 + 4 A * 6 + / When I test this in a calculator, it gives different results. Another problem is that ...

*April 15, 2013*

**biology**

i am researching an article and am having trouble understanding the title. can someone please explain to me in simple terms: Deficiency of a Beta-arrestin-2 signal complex contributes to insulin resistance. so what is a beta arrestin 2 signal complex?

*April 15, 2013*

**Chemistry**

radioactive sodium chloride is appropriate for diagnosing circulatory problems, but radioactive xenon is helpful in searching for lung problems. Explain why. I understand different elements are used for specific parts of the body but I don't understand this question. ...

*April 14, 2013*

**physics**

A 22.0 Ω, 11.0 Ω, and 6.00 Ω resistor are connected in parallel to an emf source. A current of 6.00 A is in the 11.0 Ω resistor.What is the potential diﬀerence across the source? Answer in units of V

*April 14, 2013*

**commerce**

cn u please help with core business activities of absa nedcor anglo american

*April 14, 2013*

**physics**

An 8.0 Ω resistor and a 4.0 Ω resistor are connected in series with a battery. The potential diﬀerence across the 4.0 Ω resistor is measured as 9 V. Find the potential diﬀerence across the battery.

*April 14, 2013*

**chemistry**

A solution of household bleach contains 5.25% sodium hypochlorite, NaOCl, by mass. Assuming that the density of bleach is the same as water, calculate the volume of household bleach that should be diluted with water to make 500.0 mL of a pH = 10.23 solution.

*April 10, 2013*

**chemistry**

The Ka of a monoprotic weak acid is 7.25 × 10-3. What is the percent ionization of a 0.167 M solution of this acid? If the concentration is more than 1000 times greater than the Ka, then you can make an assumption that simplifies the algebra needed to solve the problem. ...

*April 10, 2013*

**chemistry**

The half-equivalence point of a titration occurs half way to the end point, where half of the analyte has reacted to form its conjugate, and the other half still remains unreacted. If 0.460 moles of a monoprotic weak acid (Ka = 3.8 × 10-5) is titrated with NaOH, what is ...

*April 10, 2013*

**chemistry**

A flask contains 0.342 g of acid and a few drops of phenolphthalein indicator dissolved in water. The buret contains 0.120 M NaOH. 20.f mL of base is needed to reach the endpoint of the titration. Assuming that the acid is monoprotic, what is the molar mass?

*April 10, 2013*

**childhood edu**

One of Rudolph Dreikur's contributions to the field of early childhood education is his belief that? A. All behavior is goal directed. B.There's a difference between behavior and misbehavior I think it's A,am I correct

*April 9, 2013*

**math**

solve the problem A drug is injected into a patient and the concentration of the drug is monitored. The drug's concentration, C(t), in milligrams after t hours is modeled by C(t) = (7t)/2t^2+4.

*April 7, 2013*

**epidemiology**

Let’s say you are a health policy expert and you are sitting in your office and you receive a phone call from a news reporter. The reporter asks you to comment for a story she is writing. She has learned from the chief of neurosurgery at Cooper University Hospital that ...

*April 5, 2013*

**epidemiology**

In a study examining associations between level of education and response to the Philadelphia Public Health Department’s emergency messages to “shelter in place” (meaning stay in your home) following an accidental release of chemicals from the Sunoco refinery in...

*April 5, 2013*

**epidemiology**

) In a recently published article authors reported on their research examining the effectiveness of compound C-4277, an anti-viral agent. This agent was tested to determine its impact on rhinoviruses, which are the leading cause of common colds. The article states that 1,800 ...

*April 5, 2013*

**chemistry**

I mean the head temp. is the higher temp., they called it like this in my university. anyway,this question in the dehydration of cyclohexanol. when we do elimination the heat temp. should be kept below 90 c, why?

*March 30, 2013*

**chemistry**

why is the head temperature kept below 90 c in the initial step of the dehydration reaction?

*March 30, 2013*

**Calculus-PLZ HELP! =)**

does the sum 3/(2^(n)-1) converge or diverge? n=1--->infinity

*March 26, 2013*

**Calculus II**

Is the series 1/(n(n+1)) convergent? n=2 to n=infinity

*March 25, 2013*

**Calculus II**

Does 3/(2^(n) +1) diverge or converge in an infinite sum?

*March 25, 2013*

**Chemistry**

Nvm figured it out

*March 22, 2013*

**Chemistry**

Why is the last step is convert to pH? We are trying to find the hydroxide-ion concentration?not the pH

*March 22, 2013*

**Chemistry**

what is the hydronium-ion concentration in a 0.35m solution of NaCO3? For carbonic acid, Ka1=4.2x10^-7 and Ka2=4.8x10^-11. (Kw=1.0x10^-14)

*March 22, 2013*

**Chemistry**

I don't press the E button i press the 10^x Button but when I divided the kw/Kb it gives me 2.083x10^-28

*March 22, 2013*

**Chemistry**

I plug in the numbers put it doesn't match any of the choices.... I get 4.81x10^-29 The choices are A)2.3x10^-35 B)6.4x10^-23 C)7.3x10^-16 D)48 E)491 Please help!!

*March 22, 2013*

**Chemistry**

What is Kc for the following equilibrium? For phosphoric acid, Ka1=6.9x10^-3, Ka2=6.2x10^-8 and Ka3=4.8x10^-13 HPO4^-2 + OH^- <==> PO4^-3 + H2O

*March 22, 2013*

**physics**

Calculate the magnitude of the gravitational force between the Earth and an m = 6.00 kg mass on the surface of the Earth. The distance to the center of the Earth from the surface is 6.37×103 km and the mass of the Earth is 5.98×1024 kg. B)Calculate the magnitude of...

*March 22, 2013*

**english**

complete the sentence please! a kite___ tries to catch a falling kite before it lands.

*March 21, 2013*

**chemistry**

How many mL of 0.40M NaOH are need to neutralize 30.0 mL of 0.50 M H2SO4 according to the following reaction. 2NaOH(aq) + H2SO4 (aq)----Na2SO4 (aq) + 2H2O(l)

*March 20, 2013*

**English**

Which senses are appealed to in these lines from Macbeth? Nay, had I pow'r, I should / Pour the sweet milk of concord into hell, / Uproar the universal peace… A. smell, taste, and touch B. hearing, sight, and smell C. sight, taste, and hearing D. hearing, taste, and ...

*March 20, 2013*

**Childhood**

Thanks :)))

*March 19, 2013*

**Childhood**

Two most common aspects of malnutrition in the u.s are: a) heart disease and obesity b) iron deficiency and heart disease c) dental decay and iron deficiency d) obesity and dental decay. I chose c) dental and iron deficiency is that right?

*March 19, 2013*

**curriculum development**

I'm using notes and Internet not text, I can't find much info

*March 19, 2013*

**Childhood**

The fundamental purpose of early childhood education should be to a) prepare children for continuing later success in elementary school. B) foster growth of developmental sequences c) foster competence in dealing with life .is letter c) correct?

*March 19, 2013*

**Chemistry**

I could use some help please. Ammmonia, NH3, can be made by reacting Nitrogen with Hydrogen. N2+3H2=2NH3 How many moles of NH3 can be made if 7.5 moles of H2 react eith enough N2? Thank-you in advance for any help

*March 18, 2013*

**College algebra**

Find the value of f(x) = -3x^2 + 12x-8

*March 15, 2013*

**Find the following inequality**

Find the following inequality. 15(x^2-1)>16x

*March 15, 2013*

**accounting**

13. A drawback to using _______ when inventory costs are rising is that the company reports lower net income. A. LIFO B. FIFO C. specific-identification costing D. average costing 14. The balance sheet format that lists assets

*March 12, 2013*

**Math**

what is a model that shows 180 divided by 9

*March 11, 2013*

**MATH**

There is a slide in the park that is 18 feet long. The ladder to the top of the slide is 7.5 feet long. If the ladder and the slide are perpendicular, what is "D", the distance from the top of the slide to the ground? Explain how you got your answer.

*March 10, 2013*