# Posts by Anne

Total # Posts: 767

**Chemistry-help**

Posted by anne on Wednesday, February 15, 2012 at 3:20pm. How to prepare 1L of 96% v/v ethanol from 99% v/v ethanol? Can you show me the calculation steps?Thanks.

**Chemistry**

How to prepare 1L of 96% v/v ethanol from 99% v/v ethanol? Can you show me the calculation steps?Thanks.

**Physics 2**

The wire in the figure below carries a current of 12 A. Suppose that a second long, straight wire is placed right next to this wire. The current in the second wire is 30 A. Use Ampère's law to find the magnitude of the magnetic field at a distance of r = 0.72 m from...

**Physics 2**

The drawing shows four insulated wires overlapping one another, forming a square with 0.050-m sides. All four wires are much longer than the sides of the square. The net magnetic field at the center of the square is 91.5 µT. Calculate the current I.

**Physics**

A horizontal wire of length 0.48 m, carrying a current of 6.8 A, is placed in a uniform external magnetic field. When the wire is horizontal, it experiences no magnetic force. When the wire is tilted upward at an angle of 19° it experiences a magnetic force of 4.00 10-3 N...

**Chemistry**

wats Kf and kb

**Math**

Gymnast Clothing manufactures expensive hockey jerseys for sale to college bookstores in runs of up to 250. Its cost (in dollars) for a run of x hockey jerseys is C(x) = 2500 + 10x + 0.2^x2(0 ≤ x ≤ 250) Gymnast Clothing sells the jerseys at $105 each. Find the ...

**Math**

The associated exponential model for the value of a deposit after t years is A(t) = 7000(1 + (0.0394/12))^12t. At the start of which year will an investment of $7,000 made at the beginning of 2007 first exceed $11,000? (Round your answer the nearest whole number.) I don't ...

**Physics**

A capacitor is constructed of two concentric conducting cylindrical shells. The radius of the inner cylindrical shell is 2.35 10-3 m, and that of the outer shell is 2.49 10-3 m. When the cylinders carry equal and opposite charges of magnitude 1.61 10-10 C, the electric field ...

**Physics**

An electron is released from rest at the negative plate of a parallel plate capacitor and accelerates to the positive plate (see the drawing). The plates are separated by a distance of 1.4 cm, and the electric field within the capacitor has a magnitude of 3.5 106 V/m. What is ...

**Chemistry - thanks**

In a thin layer chromatography (TLC)experiment,the TLC plate was pre-developed in the development chamber containing the mobile phase (to remove any contaminants before use),then air dried. On the same day,the TLC plate was then spotted with the sample & standard and placed in...

**Chemistry-help needed**

I have a question on thin layer chromatography (TLC). My mobile phase (i.e. developing solvent) is a mixture of 2 non-polar solvents. After preparing the mobile phase, is it necessary to pour some into the developing chamber to saturate the chamber or should we only pour the ...

**Algebra**

I have 100 feet to surround three sides of a rectangle. What is the largest area that I can enclose?

**Physics**

Three point charges, -6.35 10-9 C, -8.20 10-9 C, and +7.75 10-9 C, are fixed at different positions on a circle. The total electric potential at the center of the circle is -2210 V. What is the radius of the circle?

**Physics**

The drawing shows a square, each side of which has a length of L = 0.25 m. Two different positive charges q1 and q2 are fixed at the corners of the square. Find the electric potential energy of a third charge q3 = -7.00 10-9 C placed at corner A and then at corner B.

**Physics**

Two point charges are fixed on the y axis: a negative point charge q1 = -26 µC at y1 = +0.21 m and a positive point charge q2 at y2 = +0.38 m. A third point charge q = +8.5 µC is fixed at the origin. The net electrostatic force exerted on the charge q by the other ...

**Physics**

Two point charges are fixed on the y axis: a negative point charge q1 = -26 µC at y1 = +0.21 m and a positive point charge q2 at y2 = +0.38 m. A third point charge q = +8.5 µC is fixed at the origin. The net electrostatic force exerted on the charge q by the other ...

**Physics**

Two charges, -15 and +4.5 µC, are fixed in place and separated by 2.8 m. At what spot along a line through the charges is the net electric field zero? What would be the force on a charge of +1 µC placed at this spot?

**Science**

"When Environmental Hazards happen, what should you do?"?

**Chemistry-please help**

Please show me the calculation steps. How do I prepare 10%w/w Hydrochloric acid from 37%w/w Hydrochloric acid? The density of 37%w/w HCl is 1.19g/ml. Thank you.

**Chemistry**

A foundry releases 6.0 U.S. tons of gas into the atmosphere every day. The gas mixture contains 2.5% sulfur dioxide (SO subscript 2) by weight. How many pounds of sulfur dioxide are released in one week? Show all work needed.

**Chemistry**

thanks for the help :)

**Chemistry**

A compound of the element A and oxygen has a mole ratio of A:O=2:3. If 8.0 grams of the oxide contains 2.4 grams of the oxygen, a. What is the atomic weight of A? b. What is the weight of one mole of the oxide? c. What theoretical weight of the oxide is formed when 28 grams ...

**algebra**

how do I solve F = 5/9 (F-32) ?

**urgent math**

sorry i forgot to put the problem. here it is: f(x)=4(x+5)^2-6

**urgent math**

without graphing, find the vertex, the azis of symemtry, and the maximum value or the minium value.

**urgent math**

complete the square to write each function in the form f(x)=a(x-h)^2+k f(x)=2x^2-20x-3

**urgent math**

find the equilibrium point for the demand and supply functions D(p)=79-8p and S(p)=37+6p, where p is the price, in dollars, D(p) is the number of units demanded, and S(p) is the number of units supplied.

**pre calc**

you are 7 miles N & 4 miles W of the cabin how do you get back to the cabin? Bearing?

**Urgent math please help**

find a quadratic function that fits the set of data points. (1,4), (-1.6), (-2,16) what did i do wrong, i got -2x^2-x+7

**math please help**

find all x-intercepts of the given function f. f(x)=3x+10ã(x) -8

**9th grade math**

simplify x^5-x^3+x^2-1-(x^3-1)(x+1)^2/(x^2-1)^2

**math **urgent****

using 100 ft of fence material and building a regular octagon garden, what is the area of the garden?

**Physics**

A vertical spring with a spring constant of 400 N/m is mounted on the floor. From directly above the spring, which is unstrained, a 0.30 kg block is dropped from rest. It collides with and sticks to the spring, which is compressed by 2.7 cm in bringing the block to a momentary...

**Physics**

A simple pendulum is swinging back and forth through a small angle, its motion repeating every 1.08 s. How much longer should the pendulum be made in order to increase its period by 0.31 s?

**Physics**

A 63.0-kg bungee jumper is standing on a tall platform (h0 = 45.8 m). The bungee cord has an unstrained length of L0 = 9.18 m and, when stretched, behaves like an ideal spring with a spring constant of k = 67.2 N/m. The jumper falls from rest, and it is assumed that the only ...

**Physics**

A 63.0-kg bungee jumper is standing on a tall platform (h0 = 45.8 m). The bungee cord has an unstrained length of L0 = 9.18 m and, when stretched, behaves like an ideal spring with a spring constant of k = 67.2 N/m. The jumper falls from rest, and it is assumed that the only ...

**Physics**

A vertical spring with a spring constant of 400 N/m is mounted on the floor. From directly above the spring, which is unstrained, a 0.30 kg block is dropped from rest. It collides with and sticks to the spring, which is compressed by 2.7 cm in bringing the block to a momentary...

**Physics**

A bungee jumper, whose mass is 83 kg, jumps from a tall platform. After reaching his lowest point, he continues to oscillate up and down, reaching the low point two more times in 9.7 s. Ignoring air resistance and assuming that the bungee cord is an ideal spring, determine its...

**Physics**

In 0.780 s, a 6.50-kg block is pulled through a distance of 3.85 m on a frictionless horizontal surface, starting from rest. The block has a constant acceleration and is pulled by means of a horizontal spring that is attached to the block. The spring constant of the spring is ...

**Literacy**

1) A strong search strategy for a search engine would include which of the following? A. Using quotation marks, hyphens, and unique words B. Entering one or two related words C. Using several synonymous terms in the search D. Reading all the hits from your first search answer...

**math-college URGENT****

in sentence form using one variable and one equation/inequality solve: sue makes $15/hour tutoring and averages $10/hour waitressing. Out of 30 hrs working time, what is the minimum # of hours she should tutor if she is to make at least $475?

**Physics**

Assume that the earth is a uniform sphere and that its path around the sun is circular. a) Calculate the kinetic energy that the earth has because of its rotation about its own axis. For comparison, the total energy used in the United States in one year is about 9.33 109 J. b)...

**Physics**

The drawing shows a model for the motion of the human forearm in throwing a dart. Because of the force applied by the triceps muscle, the forearm can rotate about an axis at the elbow joint. Assume that the forearm has the dimensions shown in the drawing and a moment of ...

**physics**

A thin uniform rod is rotating at an angular velocity of 6.7 rad/s about an axis that is perpendicular to the rod at its center. As the drawing indicates, the rod is hinged at two places, one-quarter of the length from each end. Without the aid of external torques, the rod ...

**chemistry**

A student placed 10 g of Mg(OH)2 into a flask and added 500ml of water. The student took 100 ml of the Mg(OH)2 solution and reacted with HCl(aq). If 13.75 ml of 0.010M HCL reacted with the OH(aq), was was the concentration of hydroxide ion in the 100 ml solution?

**Physics**

A car is being driven along a country road on a dark and rainy night at a speed of 20 m/s. The section of road is horizontal and straight. The driver sees that a tree has fallen and covered the road ahead. Panicking, the driver locks the breaks at a distance of 20m from the ...

**physics**

A dam blocks the passage of a river and generates electricity. Approximately 57,000 kg of water fall each second through a height of 19 m. If one half of the gravitational potential energy of the water were converted to electrical energy, how much power would be generated?

**physics**

A dam blocks the passage of a river and generates electricity. Approximately 57,000 kg of water fall each second through a height of 19 m. If one half of the gravitational potential energy of the water were converted to electrical energy, how much power would be generated?

**physics**

While you sleep, your body is using energy at a rate of 77 W. How many food calories are used during an eight hour period? One food calorie is equal to 4186 joules.

**Precalculus**

Complete the following identity secx-1/secx=? I have four multiple choice options and can't seem to work my way to either one. A) secx cscx B)1+cotx C)sinx tanx D)-2tan^2x

**CHEMISTRY PLEASE HELP**

1) What effect would each of the errors described below have on the concentration of potassium hydrogenphthalate?

**Physics**

Two stars in a binary system orbit around their center of mass. The centers of the two stars are 7.80 x 10^11 m apart. The larger of the two stars has a mass of 3.50 x 10^30 kg, and its center is 3.00 x 10^11 m from the system's center of mass. What is the mass of the ...

**Physics**

Two stars in a binary system orbit around their center of mass. The centers of the two stars are 7.80 1011 m apart. The larger of the two stars has a mass of 3.50 1030 kg, and its center is 3.00 1011 m from the system's center of mass. What is the mass of the smaller star?

**Physics**

Two stars in a binary system orbit around their center of mass. The centers of the two stars are 7.80 1011 m apart. The larger of the two stars has a mass of 3.50 1030 kg, and its center is 3.00 1011 m from the system's center of mass. What is the mass of the smaller star?

**Chemistry - please help-thanks**

Posted by anne on Saturday, October 15, 2011 at 1:03am. Hi, Please advise on the following: - A procedure for the determination of Impurities A & B in a compound says to use a 4.6 x 150mm x 3um column (stationary phase: octadecylsilyl silica gel). The relative retention time ...

**Chemistry-Bob please help-Thanks**

Hi, Please advise on the following: - A procedure for the determination of Impurities A & B in a compound says to use a 4.6 x 150mm x 3um column (stationary phase: octadecylsilyl silica gel). The relative retention time with reference to the Principal Peak is: - 1) about 0.2 ...

**Chemistry-Bob please help**

Posted by anne on Friday, October 14, 2011 at 6:30pm. Hi, I have a question on HPLC (high performance liquid chromatography). The procedure says to use a 4.6 x 150mm x 3um column. The relative retention time of Impurity B with reference to the main peak is about 0.5 (i.e the ...

**Chemistry-please help**

Posted by anne on Friday, October 14, 2011 at 6:30pm. Hi, I have a question on HPLC (high performance liquid chromatography). The procedure says to use a 4.6 x 150mm x 3um column. The relative retention time of Impurity B with reference to the main peak is about 0.5min. If I ...

**Chemistry**

Hi, I have a question on HPLC (high performance liquid chromatography). The procedure says to use a 4.6 x 150mm x 3um column. The relative retention time of Impurity B with reference to the main peak is about 0.5min. If I use a 4.6 x 100mm x 2.7um column, will the relative ...

**Pre-Calculus**

Could someone help me with this-we learned this today in school but I'm not getting it now that I'm home with my homework-I have lots of these to do can someone help with this one and then maybe it'll click-thank you Find (sqrt3/2 -1/2i)^4 by using DeMoivre's ...

**Algebra**

2 pumps can fill a water tank in 45 minutes when working together. Alone, the second pump takes 3 times longer than the first to fill the tank. How long does it take the first pump alone to fill the tank? Show all work

**Math**

Zachary saved x nickels and y dimes last month. Lily saved x nickels and 2y dimes. Lily saved $2 more than Zachary and the total number of her dimes is 4 times the total number of her nickels. (a) How much coins does Zachary have? (b) How much did Lily save? (c) How much did ...

**US government**

What is the freedom from prior restraint?

**Finance**

A state's lottery winner is promised $200,000 a year for 3 years(starting at the end of the first year). Interes rate is annually 7 percent on its fund. How much is the present value of this lottery?

**trig**

Cos(2x+30)-Sin(3x-20)

**math**

Zachary saved x nickels and y dimes last month. Lily saved x nickels and 2y dimes. Lily saved $2 more than Zachary and the total number of her dimes is 4 times the total number of her nickels. (a) How much coins does Zachary have? (b) How much did Lily save? (c) How much did ...

**physics**

A woman rides a carnival Ferris wheel at radius 16 m, completing 4.2 turns about its horizontal axis every minute. What are (a) the period of the motion, and the magnitude of her centripetal acceleration at (b) the highest point and (c) the lowest point?

**English**

with people

**English**

What are the ways of getting acquainted?

**french**

What would I use before etait in this statement ?"Nous avons beaucoup aime notre sejour en France . ..... etait splendide."

**environmental science**

what are the environmental parameters of intertidal zone?

**Chemistry**

I have 2 chemicals, A & B. Note: both do not contain buffer salts. Chemical A expires 1 week later. Chemical B expires next year. I prepare solution C (general laboratory reagent)containing Chemicals A & B. When assigning the expiry date of solution C, does this mean the ...

**CHEMISTRY**

Discuss in detail the healthcare applications of chemical reactions. Which chemical reactions would you consider to be of importance to healthcare professionals? Why? In which situations are these chemical reactions useful to healthcare professionals?

**Physics**

He meant 'Physics' as the subject instead of 'Tamucc', which stands for Texas A&M University - Corpus Christi. He must be taking the summer physics class at TAMUCC.

**maths**

1)Please check that you entered this answer correctly, as it is written now I'm not convinced it can be factored. 2)6x^2+5x-4=0 (3x+4)(2x-1) 3)x^2=3x x^2-3x=0 x(x-3) 4)x(x-3)=-2 x^2-3x=-2 x^2-3x+2 (x-2)(x-1) 5)4x^2+11x+6 (4x+3)(x+2)

**Calculus**

A car passes by a certain point at t = 0 hours heading east at 40 miles/hour. At t = 1 hour, another car passes by the same point heading north at 50 miles/hour. Which of the following functions equals the distance L (in miles) between the two cars as a function of t, for t is...

**algebra**

12(x-6)=2(x-9) x equals?

**math**

Sunae's group of close friends are going to fifth grade in September. All are going to Belleview Elementary and their homerooms will be rooms 12, 14, or 16. All of her friends but 4 are going to room 12, all but 4 are going to room 14, and all but 4 are going to room 16. ...

**Physics**

The helicopter view in the figure below shows two people pulling on a stubborn mule. Assume that F1 is 130 N, and F2 is 65 N. The forces are measured in units of newtons (N). (a) Find the single force that is equivalent to the two forces shown. In both magnitude and direction...

**Physics**

An astronaut takes a space trip to newly discovered palnet X. measurements from earth indicate that: Mx=3Me and Rx=2Re. What is the acceleration of gracity gx on this planet as a multiple of ge?

**Physics**

can u explain it in another way

**Physics**

Suppose the stone is thrown at an angle of 32.0° below the horizontal from the same building (h = 49.0 m) as in the example above. If it strikes the ground 69.3 m away, find the following. (Hint: For part (a), use the equation for the x-displacement to eliminate v0t from ...

**Physics**

In a physics lab experiment, a spring clamped to the table shoots a 18 g ball horizontally. When the spring is compressed 20 cm, the ball travels horizontally 4.9 m and lands on the floor 1.3 m below the point at which it left the spring. What is the spring constant?

**Physics**

A 18 kg child slides down a 4.0 m-high playground slide. She starts from rest, and her speed at the bottom is 2.8 m/s. What is the change in the thermal energy of the slide and the seat of her pants?

**physics**

A ball is thrown vertically upward with a speed of +12.0 m/s. How long does the ball take to hit the ground after it reaches its highest point? What is its velocity when it returns to the level from which it started?

**biology**

can alcohol go through a visking tubing?

**math**

At Andrews sweet shop almond fudge costs $5.23 per pound, and vanilla fudge costs $4.17 per pound. Allison buys 0.75 pound of almond fudge and 1.25 pounds of vanilla fudge. About how much will Allison pay altogether (excluding tax)?

**Chemistry-atoms**

A. How many protons are in one atom of fluorine - 19? B. How many neutrons are in one atom of potassium - 39? C. How many electrons are in one neutral atom of V - 51? D. What is the symbol for the element that has 78 protons? E. What is the symbol for the neutral atom that has...

**Physics**

How do I find Period T(s) and Period^2 T^2 (s^2), given mass(kg) = 0.1 and Average time for ten vibrations (s) = 5.05?

**physics**

At what distance (in m) from a 3.8 mC charge is the electric potential equal to 32 V? (k = 9 x 109 Nm2/C2)

**Psycology**

Psychology and Health Problems Paper

**statistics**

A population is normally distributed with a mean of 40 and a standard deviation of 6. For samples of size 10, what is the probability that the sample mean will be more than 42?

**medical coding**

What OB/GYN subspecialties specializes in the use of a hysteroscopy?

**computer science**

Opera Mobile is an example of: a smartphone. a wireless ISP. SmartMedia. a microbrowser.

**Physics**

2 trains with 132Hz horns approach one another. The slower train has a speed of 25m/s. what is the speed of the fast train if an observer standing near the tracks between the trains hears a beat frequency of 5.2 Hz?

**math**

give exact and approximate solutions to three decimal places y^2-12y+36=4

**Organic Chemistry**

Starch

**Organic Chemistry**

What is the substrate of the enzyme amylase?