# Posts by erica

Total # Posts: 613

**Chemistry**

thank you so much for the explanation

*September 18, 2012*

**Chemistry**

I need help please I am so confused. How much dry solute would you take to prepare each of the following solutions from the dry solute and the solvent? I know the MM of KCl is 74.55 107g of 0.535m KCl

*September 18, 2012*

**Chemistry**

thank you so very much

*September 17, 2012*

**Chemistry**

To what volume should you dilute 43.5mL of a 4.20M KI solution so that 24.0mL of the diluted solution contains 2.80g of KI? Please if you can explain it to me I am so confused.

*September 17, 2012*

**Chemistry**

A sample of 2.00 mol O2 (assumed perfect) is originally confined in a 20.0L at 273K and 2.24 atm. it undergoes reversable adiabatic expansion until the volume has increased by a factor of 3. Calculate q, w, delta u, delta h, and delta t. Cv=7/2R and cp=5/2R

*September 6, 2012*

**calculus**

Find the limit if it exist lim t-->pi/3 (tan(t)/t)+1

*September 6, 2012*

**calculus**

Find a delta for any epsilon given: x^2+x-6/x+3 and x0=-3

*September 6, 2012*

**chemistry**

write a step by step procedure explaining how you will separate the sand, potassium chloride, and iron

*September 6, 2012*

**math**

what would the following equation be in vertex form. y=-9x squared+72x+81. I have tried for hours and i cannot figure it out

*September 1, 2012*

**Physics**

The left ventricle of the heart accelerates blood from rest to a velocity of + 29.8 cm/s. (a) If the displacement of the blood during the acceleration is + 2.68 cm, determine its acceleration (in cm/s2). (b) How much time does blood take to reach its final velocity?

*August 31, 2012*

**math**

all these numbers kind of confuse me. Im not sure what ^ means. Right now the only equation i have learned is y= a(x-s)(x-t)

*August 31, 2012*

**math**

the dome over a town hall has a parabolic shape. the dome measures 48 m across and rises 12m at the centre. A vertical column needs to be attached to the dome at a point that is 4m away from its rim. How tall is the dome at this point? Also, what is the equation that models ...

*August 31, 2012*

**math**

how would I measure a distance or object using right angled trig?

*August 14, 2012*

**math**

Select a real life object (tree flagpole ect) or distance that cannot be measured directly. Describe how to measure an object or distance by right-angled trigonometry using methods such as SOH CAH TOA or the pythogrorean theorem. Organize all the data you need and preform the ...

*August 14, 2012*

**math**

a popular tourist attraction in ottawa is the Peace tower, which rises from the Center Block of the Parliment buildings. Describe at least one method that you could use to estimate the height of the tower, including the measurments you would need to make. Include labelled ...

*August 13, 2012*

**math**

a popular tourist attraction in ottawa is the Peace tower, which rises from the Center Block of the Parliment buildings. Describe at least one method that you could use to estimate the height of the tower, including the measurments you would need to make. Include labelled ...

*August 12, 2012*

**reading**

the reason the test questions and answers is up there because its all wrong answers on purpose for cheaters. when i first started i passed two test by myself. then the last three test try to cheat to use the answers and failed three test then retook them by myself and passed. ...

*July 9, 2012*

**alg**

An amplifier has an input power of 5 mW. The output power is 100 mW. What is the decibel gain to the nearest decibel?

*June 28, 2012*

**algebra ll**

9y2+4=12y how to solve this equation using the zero factor

*June 27, 2012*

**Math**

What is the image of A(4,4) under a reflection in the point P(4,-2)?

*June 10, 2012*

**Math**

Jack is married to Jill. Their son, Junior, asked each of them to reveal their ages. Junior’s parents decided to tell him, but in the form of a puzzle. Jack told Junior, “If you reverse the digits in my age, you get your mother’s age. Jill told her son, “...

*May 29, 2012*

**Math**

At Irv's Rental Shop, Irv rents all kinds of cycles: unicycles, tandem bikes, regular bikes, and even tricycles for little kids. He parks all the cycles in front of his shop with a helmet for each rider strapped to the cycles. This morning Irv counted 57 helmets and 115 ...

*May 15, 2012*

**statistics**

a mean score on a standardized test is 50 with a standard deviation of 10. What are the following: 1. what scores fall between -1 and +1 standard deviation? 2. what percent of all scores fall between -1 and +1 standard deviation? 3. what score falls at +2 standard deviations? ...

*May 11, 2012*

**statistics**

where is this formula located on excel?

*May 11, 2012*

**statistics**

a final exam in statistics has a mean of 73 with a standard deviation of 7.73. Assume that a random sample of 24 students is selected and the mean test score of the sample is computed. What percentage of sample means are less than 70?

*May 11, 2012*

**Math**

Tino conducted a survey of all the eighth graders in his school for his math project. He asked each student how much he or she spent on school supplies at the beginning of the year (rounded to the nearest dollar). He also calculated the average amount spent and ...

*May 8, 2012*

**math 101**

al flynn wants to buy a van that cost 16,000 with an interst charge of 2,000. Al figures he can afford a monhtly oayment of 700 per month, If there aew 24 equal payments required could al afford the van.

*May 6, 2012*

**physics**

This looked a little sloppy imo... Here's my example 1. Find most probably velocity of Krypton v = √[(2*8.314J/K*273K)/(0.083798 kg)] = 237.75 m/s Find the ratio of each velocity 205/237.75 = .8808 The average is .8851 207/237.75 = .8894 Find the ratio of change in ...

*April 18, 2012*

**Math**

Nico was stunned when he opened the mail. Here was a check for $322.50! This was the interest he earned on his investment. One year ago Nico had been given $5,000. His parents made him put it in the bank and save it for college, but they said he could keep the interest it ...

*April 16, 2012*

**chem**

Hey you guys how do you find the moles of .75g of He

*April 16, 2012*

**Chemistry**

How can you determine which colorless liquid is less dense?

*April 6, 2012*

**physics**

Could you elaborate on this?

*April 6, 2012*

**Math**

The population of humorville is 8,500 people. In this town, jokes travel fast. In one hour, each person who hears a joke tells three other people who have not heard it, and tells no one else. Last Friday, a visitor from out of town told the police chief a new joke at 10:00a.m...

*March 19, 2012*

**Statistics**

Suppose that people's heights (in centimeters) are normally distributed, with a mean of 165 and a standard deviation of 6. We find the heights of 100 people. (a) How many would you expect to be between 157 and 173 cm tall? (b) How many would you expect to be taller than ...

*March 14, 2012*

**Math**

thanks steve

*March 13, 2012*

**Math**

I snap my fingers now. in one second, i snap them again. I wait two seconds and snap them a third time. I wait four seconds before snapping them again. then i wait eight seconds, then sixteen, and the pattern continues on. the interval between snaps doubles each time How many ...

*March 13, 2012*

**Chemistry**

2NaOH+2Al+2H2O --> 2NaAlO2+3H2 here is the reaction. If i am trying to find the mass of hydrogen produced and i am trying to convert .95 moles Al to moles H, which number from the reaction do I use for H when converting from moles to moles? Do I 6 because that's the ...

*March 9, 2012*

**Math**

the design below grows each day, as shown. if the pattern continues to grow like this, how many tiles will there be in the design on the tenth day? on the fiftieth day? Day 1 1 tile Day 2 5 tiles Day 3 13 tiles

*March 5, 2012*

**Algebra 2**

On some tubes of caulking, the diameter of the circular nozzle opening can be adjusted to produce lines of varying thickness. The table shows the length l of caulking obtained from a tube when the nozzle opening has diameter d and cross-sectional area A. 48. Determine whether ...

*March 3, 2012*

**math**

Mr. Jaskson's lunch cost $8.00 plus 8% sales tax. He tipped the server 15% of total bill after sales tax was added. How much did Mr. Jackson spend in all?

*February 26, 2012*

**chemistry**

BrO^3- + 3Sb^3+ + 6H^+ -----> Br^- + 3Sb^5+ +3H2o

*February 24, 2012*

**Physics**

well that doesn't look readable. the answer should still be right but I'll rewrite how I did the math Cfs = mv^2/rFn = ((2πr/T)^2)/r(g) = (4(π^2)r)/g(T^2) Cfs = 4(π^2)(0.159 m) / (9.8 m/s^2)(1.50 s)^2 = 0.28467

*February 20, 2012*

**Physics**

Static Friction Coefficient = Cfs For of Static Friction = Fs Normal Force = Fn Centripetal Force = Fc mass = m radius = r speed = v period of time = T Fs = Cfs * Fn so Cfs = Fs/Fn Fc = Fs and since Fs = mv^2/r Cfs = Fs/Fn = mv^2/r*Fn v = 2πr/T and Fn = mg so.... mv^2 (2...

*February 20, 2012*

**geometry**

the perimeter of quadrilateral jklm is 90 centimeters. which is the length of side kl

*February 16, 2012*

**Probability**

In a Cc x Cc crossing of peas, 5 offspring are of genotype CC, 12 are of genotype Cc, and 6 are of genotype cc. What is the probability of this event?

*February 16, 2012*

**Chemistry**

How many formula units of (NH4)3PO4 are present in 12.25 g of K3PO4? Please explain so I can do these in the future! Very confused.

*February 15, 2012*

**Chemistry**

So the answer is 4.88?

*February 15, 2012*

**Chemistry**

If 2.44 moles of H2 are reacted with excess Cl2, how many moles of Hcl can be produced? Please explain.

*February 15, 2012*

**Physics**

Ultrasound with a frequency of 4.275 MHz can be used to produce images of the human body. If the speed of sound in the body is the same(1.79 km/s) as in salt water, what is the wavelength in the body?

*February 6, 2012*

**algebra**

-13^2-4(-13)(36) That answer squared

*February 6, 2012*

**English**

What kind of clause would (when painters looked at rapidly moving horses.) would it be a adverb,adjective, or noun?

*February 6, 2012*

**Physics**

A car's initial velocity of 13.5 m/s accelerates at a rate of 1.9 m/s^2 for 6.2 s. Then, it accelerates at a rate of -1.2 m/s^2 until it stops. 1) What is the car's maximum speed? 2) What is the total time from the start of the first acceleration until the car is ...

*February 1, 2012*

**Physics**

A car is speeding at 33.4 m/s. A police car starts in pursuit from rest when the car is 100 m past the cruiser. At what rate must the cruiser accelerate to catch the speeder before the state line, 1.2 km away from the speeding car? Include all steps if possible please, so that...

*February 1, 2012*

**English- Infinitive phrases**

That website is very helpful! Thank you :) So, because there is no "to" would the infinitive phrase include the verb too? : "made him work hard"

*January 29, 2012*

**English- Infinitive phrases**

For this question, the directions say to name the TWO infinitive phrases in this sentence... His wish to succeed as an architect made him work hard. I know that "to succeed as an architect" would be one infinitive phrase, but there isn't another "to" ? ...

*January 29, 2012*

**Probability**

Assume that 20% of a very common insect species in your study area is parasitized. Assume that insects are parasitized independently of each other. If you collect 10 specimens of this species, what is the probability that no more than 2 specimens in your sample are parasitized...

*January 27, 2012*

**Probability**

A drug company claims that a new headache drug will bring instant relief in 90% of all cases. If a person is treated with a placebo, there is a 20% chance that the person will feel instant relief. In a clinical trial, half the subjects are treated with the new drug and the ...

*January 27, 2012*

**Probability**

A drawer contains six bags numbered 1-6, respectively. Bag i contains i blue balls and 2 green balls. You roll a fair die and then pick a ball out of the bag with the number shown on the die. What is the probability that the ball is blue? Thank you!

*January 27, 2012*

**Probability**

A screening test for a disease shows a positive test result in 95% of all cases when the disease is actually present and in 20% of all cases when it is not. When the test was administered to a large number of people, 21.5% of the results were positive. What is the prevalence ...

*January 27, 2012*

**Probability**

You toss a fair coin four times. Find the probability of no more than three heads given that at least one toss resulted in heads. Thank you very much!!

*January 27, 2012*

**Geometry**

The ratio of the side lengths of a triangle. Is 2:4:5 and the perimeter is 55 cm. What is the length of the shortest side?

*January 25, 2012*

**Chemistry**

would you multiple 500x0.20 and then divide the amount with 1.30

*January 20, 2012*

**Chemistry**

large dose of vitamin C are supposed to cure the common cold. One commercial over-the-counter product consists of 500-mg tablets that are 20% by weight vitamin C. How many tablets should one take for a 1.30g dose of vitamin C?

*January 20, 2012*

**chemistry**

As the temperature of a gaseous substance is decreased at constant pressure, it will undergo a series of physical changes. Which is the correct sequence of physical states that will be encountered? a.Liquid, solid, gas b.Gas, solid, liquid c.Solid, liquid, gas d.Gas, liquid, ...

*January 20, 2012*

**chemistry**

As the temperature of a gaseous substance is decreased at constant pressure, it will undergo a series of physical changes. Which is the correct sequence of physical states that will be encountered?

*January 20, 2012*

**History**

Discuss why England's North American colonial empire had outstripped those of her European rivals by the end of the seventeenth century?

*January 18, 2012*

**Probability**

Assume that P(A) = 0.4, P(B) = 0.4, and P(A∪B) = 0.7. Find P(A∩B) and P(A complement ∩ B complement).

*January 17, 2012*

**Probability**

In the game of poker, determine the number of ways a straight (five cards with consecutive values, such as A 2 3 4 5 or 7 8 9 10 J or 10 J Q K A, but not all of the same suit) can be picked.

*January 17, 2012*

**Probability**

Twelve children are divided up into three groups, of five, four, and three children, respectively. In how many ways can this be done if the order within each group is not important? Thank you so much!

*January 17, 2012*

**Probability**

Automated chemical synthesis of DNA has made it possible to custom-order moderate length DNA sequences from commercial suppliers. Assume that a single nucleotide weighs about 5.6 X 10^-22 grams and that there are four kinds of nucleotides. If you wish to order all possible DNA...

*January 16, 2012*

**Algebra 2**

From 1990 to 1994, the mail order sales of health products in the United States can be modeled by S = 10t 3 + 115t 2 + 25t + 2505 where S is the sales (in millions of dollars) and t is the number of years since 1990. In what year were about $3885 million of health products ...

*December 30, 2011*

**Algebra 2**

Find the value of c that makes the expression a perfect square trinomial. Then write the expression as the square of a binomial. I didn't really understand what that meant. x^2-23x+c x^2-(2/7)x+c

*December 5, 2011*

**Chemistry**

a sample of gas has the pressure of 1120 mmhg and volume of 2.00 L. if the pressure is changed to 0.155 atm calculate the new volume

*November 29, 2011*

**Calc**

Describe in words the set of all points in R³ that satisfy the following expressions: a) z=0 b) z≥0 c) y≤0

*November 7, 2011*

**s.s**

I just took this exam and the answer is, in fact, cotton yarn.

*November 2, 2011*

**Calc**

Solve: du/dt = (sin t) / (u^2 + 1) So far I got: arctan u = -ln |csc t + cot t| + C I'm not sure where to go from there. Thank you so much for the help!

*October 31, 2011*

**Calc**

How do you take the integral of dy/(y^2 + 4)?

*October 30, 2011*

**Calculus**

What is the limit as t→∞ of L(t)? L(t) = 34 - 32e^(-0.0719t) Thank you so much!

*October 30, 2011*

**Calculus**

Suppose that you follow the size of a population over time. When you plot the size of the population versus time on a semilog plot (i.e., the horizontal axis, representing time, is on a linear scale, whereas the vertical axis, representing the size of the population, is on a ...

*October 30, 2011*

**Calc**

Find the integral from -∞ to -1 of 1/(1+x²) dx. I started working the problem out, and so far I got the lim as z→-∞ of [arctan (-1) - arctan (z)]. I'm a little bit confused exactly what is means when you plug -∞ into z, and how to solve the ...

*October 24, 2011*

**Calculus**

How do you solve the integral from 0 to 1 of x arctan x dx?

*October 24, 2011*

**Calculus**

How do you integrate 3∫(1)/(x²+1)² dx ? Thank you!

*October 19, 2011*

**Calc**

Use substitution to evaluate the indefinite integral: The integral of [ (sq. root (1 + ln x)) ((ln x)/x) dx] Im confused on what i should substitute u and du for. Thank you so much!!

*October 19, 2011*

**Calculus**

Evaluate the indefinite integral: ∫ from 1 to 2 of ln (x²e^x) dx Thank you for your help!!

*October 18, 2011*

**Calculus**

Use either substitution or integration by parts to evaluate the integral: ∫(x+2)/(x²+2) dx Thank you!!

*October 18, 2011*

**Calc**

First make an appropriate substitution and then use integration by parts to evaluate the indefinite integrals: ∫ sinx cos³x e^(1-sin²x) dx I was going to substitute u= 1 - sin²x, but then i got du = ½ sinxcosx - ½ xdx, so im stuck. Thank you ...

*October 18, 2011*

**Calc**

Use integration by parts to evaluate the integral. ∫ from 1 to 4 of (√x) (ln√x) dx Im not really sure what to choose for u and dv. Thank you so much for the help!!

*October 18, 2011*

**Calculus**

F(x) = cos(x) • the integral from 2 to x² + 1 of e^(u² +5)du Find F'(x). When i did this, i got: -2xsin(x)e^((x²+1)² + 5) But my teacher got: -sin(x) • the integral from x² + 1 of e^(u² +5)du + 2xcos(x)e^((x²+1)² + 5) Do ...

*October 17, 2011*

**physics**

To plot the potential energy, simply plug your givens into the equation U=(1/2)kx^2. You should get a parabola that goes to 0 in the center. To determine the turning points of the block, use the law of conservation of energy. You know that Ui+Ki = Uf+Kf since there is no ...

*October 16, 2011*

**Statistics**

The production process of computer parts uses two machines one old & one new. If the old machine is used the probability that the defected part is produced is .13 if the new machine is used the probability that the defective part is produced is .04. moreover, the new machine ...

*October 12, 2011*

**Physics**

F=kx F (tension of the strand)=1.2 pN x (displacement)=26 µm Solve for k, which is the spring constant. You may need to convert your unit measurements, as your answer's unit will come out in pN/µm instead of the standard N/m. (I know this is a little late, but ...

*October 12, 2011*

**Calculus**

A particle moves along the x-axis with velocity v(t) = -(t-3)² + 5 for [0,6]. a) Find the average velocity of this particle during the interval [0,6]. b) Find a time t* ∈ [0,6] such that the velocity at time t* is equal to the average velocity during the interval [0...

*October 10, 2011*

**Calc**

Recall that the acceleration a(t) of a particle moving along a straight line is the instantaneous rate of change of the velocity v(t); that is, a(t) = d/dt v(t) Assume that a(t) = 32 ft/s². Express the cumulative change in velocity during the interval [0, t] as a definite...

*October 10, 2011*

**Calc**

Find the areas of the regions bounded by the lines and curves by expressing x as a function of y and integrating with respect to y. x = (y-1)² - 1, x = (y-1)² + 1 from y=0 to y=2. I graphed the two functions and the do not intersect? Does it matter? Or do I still ...

*October 10, 2011*

**Chem**

Calculate the amount (in moles) of H₂O in 2.00g of Na₂CO₃ ⋅ 10H₂O. Thanks so much!!

*October 8, 2011*

**Chem**

The field of nanotechnology offers some intriguing possibilities, such as the creation of fibers one atom wide. Suppose you were able to string together 1.00 mol Ag atoms, each of radius 144 pm, into one of these fibers by encapsulating them in carbon nanotubes. How long would...

*October 8, 2011*

**Chem**

Calculate the amount (in moles) of Cu²+ ions in 3.00g of CuBr₂. Thank you so much for the help!!

*October 8, 2011*

**Chem**

Epsom salts consist of magnesium sulfate heptahydrate. Write its formula. a) How many atoms of oxygen are in 5.15g of Epsom salts? b) How many formula units of the compound are present in 5.15g? c) How many moles of water molecules are in 5.15 g of Epsom salts? Thank you so ...

*October 7, 2011*

**physics**

if a car can accelerate at 6m/s2, how fast can it accelerate if it is towin an identical car behind it?

*October 5, 2011*

**Calculus**

Assume that a>0. Evaluate the integral from 0 to a of x dx by approximating the region bounded by y=x and the x-axis from 0 to a with rectangles. Use equal subintervals and take right endpoints.

*October 2, 2011*