# Rob

Popular questions and responses by Rob-
## Chemistry

Use the data given below to construct a Born - Haber cycle to determine the electron affinity of Br? DH°(kJ) K(s) → K(g) 89 K(g) → K⁺(g) + e⁻ 419 Br2(l) → 2 Br(g) 193 K(s) + 1/2 Br2(g) → KBr (s) -394 KBr(s) → K⁺(g) + Br⁻(g) 674 I know

*asked on December 8, 2012* -
## general chem

Determine the oxidation number for the indicated element in each of the following compounds: (a) Co in LiCoO2, (b) Al in NaAlH4, (c) C in CH3OH (methanol), (d) N in GaN, (e) Cl in HClO2, (f) Cr in BaCrO4.

*asked on October 9, 2011* -
## physics

A small rubber wheel is used to drive a large pottery wheel, and they are mounted so that their circular edges touch. The small wheel has a radius of 1.7 cm and accelerates at the rate of 6.9 rad/s^2, and it is in contact with the pottery wheel (radius

*asked on October 18, 2010* -
## general chem

Using the activity series (Table 4.5), write balanced chemical equations for the following reactions. If no reaction occurs, simply write NR. (a) Nickel metal is added to a solution of copper (II) nitrate; (b) a solution of zinc nitrate is added to a

*asked on October 9, 2011* -
## math

Lois wants to send a box of oranges to a friend by mail. The box of oranges cannot exceed a mass of 10 kg. If each orange has a mass of 200g, what is the maximum number she can send?

*asked on April 18, 2012* -
## general chem

Calculate the molarity of a solution made by dissolving 12.5 grams of Na2CrO4 in enough water to form exactly 550 mL of solution. (b) How many moles of KBr are present in 150 mL of a 0.275 M solution? (c) How many milliters of 6.1 M HCl solution are needed

*asked on October 9, 2011* -
## Math

It takes an older pump 4 times as long to drain a certain pool as it does a newer pump. Working together, it takes the two pumps 4 hours to drain the pool. How long will it take the older pump to drain the pool working alone?

*asked on January 31, 2016* -
## Statistics

Use the given data to find the minimum sample size required to estimate a population proportion or percentage. Margin of error: 0.06; confidence level 90% ^p and ^q unknown n= (round up to the nearest integer)

*asked on April 30, 2013* -
## chemistry

How many grams of NaOH are present in 5.0 mL of a 1.0% (m/v) NaOH solution?

*asked on April 25, 2008* -
## Statistics

A study of 420,048 cell phone users found that 135 of them developed cancer of the brain or nervous system. prior to this study of cell phone use the rate of such cancer was found to be 0.0333% for those not using cell phones. Complete parts (a) and (b) a.

*asked on April 30, 2013* -
## trig

find the exact value of cos(theta) if the terminal side of angle(theta) contains the point (-3,5)

*asked on January 31, 2010* -
## Geometry

QS−→ bisects ∠PQR, m∠PQS=(4y−10)∘, and m∠SQR=(2y+10)∘. Find m∠PQR.

*asked on December 25, 2019* -
## math

Find the volume of the figure. the figure is in the website below. For calculations involving π, give both the exact value and an approximation to the nearest hundredth of a unit. Let d = 8 and h = 18. www.webassign.net/aufexc3/7-4-002-alt.gif

*asked on December 7, 2018* -
## Physics

Mixing copper and zinc atoms produces the alloy brass. What would be produced with the fusion of copper and zinc nuclei?

*asked on April 25, 2008* -
## Trigonometry

What is cos (pi/2 - x) secx using the fundamental identities to simplify the expression. I think I have the right answer but I want to check to make sure. Well, cos (pi/2 - x) is something you should've seen already. It's just another name for sin(x).

*asked on October 18, 2006* -
## Math (Confused)

A certain economy's consumption function is given by the equation C(x)=0.75x+5 where C(x) is the personal consumption expenditure in billions of dollars and x is the disposable personal income in billions of dollars. Find C(0), C(50), and C(100). a.

*asked on October 17, 2016* -
## Physics

Two wires run from the top of a pole 2.6m tall that supports a volleyball net. The two wires are anchored to the ground 2.0m apart, and each is 2.0m from the pole. The tension in each wire is 100N. here are the dimensions. I do not understand how to setup

*asked on March 17, 2013* -
## Trigonometry

A little boy is flying a kite. The string of the kite makes an angle of 30 dgrees with the ground. If the height of the kite is h equals 15 m, find the length (in meters)of the string that the boy has used.

*asked on January 24, 2010* -
## Geometry

Find the circumference and area of a circle with radius 8 cm. Express your answer in terms of π.

*asked on December 25, 2019* -
## Math Help

A server purchased at a cost of $108,000 in 2002 has a scrap value of $18,000 at the end of 5 years. Find the linear equation expressing the server's book value at the end of t years. a- V(t)=108,000 b- V(t)=108,000t-18,000t c- V(t)=18,000t+108,000 d-

*asked on October 17, 2016* -
## Precalculus

Write the sum using sigma notation. -3/8 + 4/7 - 5/6 + 6/5 - 7/4+ 8/3

*asked on July 1, 2016* -
## physics

Two wires run from the top of a pole 2.6 tall that supports a volleyball net. The two wires are anchored to the ground 2.0 apart, and each is 2.0 from the pole. The tension in each wire is 100. I do not understand how to setup work. if could show I would

*asked on March 17, 2013* -
## chemistry

what is the balanced equation for the reaction of potassium dichromate and potassium hydrogen phthalate?

*asked on January 10, 2013* -
## Science

A car's engine is only 12% efficient at converting chemical energy in gasoline into mechanical energy. If it takes 1.8 x 104 N of force to keep the car moving at a constant speed of 21 m/s, how much chemical energy would be needed to move the car a

*asked on July 18, 2012* -
## math

what is the lateral area of a regular pyramid with a base 6 and slant height 8?????????????

*asked on March 14, 2012* -
## Chemistry

If you are using 5.25% (mass/mass) bleach solution and you determine that the density of the bleach solution is 1.08 g/mL, how many moles of sodium hypochlorite are present in a 4.00 mL sample?

*asked on January 31, 2012* -
## statistics

Part 1) A physical therapists wishes to determine whether an exercise program increases flexibility. He measures the flexibility (in inches) of 12 randomly selected subjects both before and after an intensive eight-week training program and obtains the

*asked on March 7, 2011* -
## Microeconomics (full version)

Pharmaceutical drugs have an inelastic demand, and computers have an elastic demand. Suppose that technological advance doubles the supply of both products (that is, the quantity supplied at each price is twice what it was). a. What happens to the

*asked on November 22, 2010* -
## Econ

In which of the following circumstances would a buyer be indifferent about buying a good? a. The amount of consumer surplus the buyer would experience as a result of buying the good is zero. b. The price of the good is equal to the buyer's willingness to

*asked on March 30, 2009* -
## Physics

Does centripetal force acting on an object in uniform circular motion do work on the object? For work, force must be in the direction of movement. Please stop posting under differing names.

*asked on June 18, 2007* -
## geography

Birth and death certificates are an example of what?

*asked on June 28, 2020* -
## biology

Use of antiseptics

*asked on June 26, 2020* -
## chemistry

What is solid?

*asked on June 25, 2020* -
## Math

The perimeter of the rectangle below is 150 units. Find the length of side PQ and write the answer with no variables. side 4x+3 Bottom: 5x

*asked on April 9, 2020* -
## Organic Chemistry

What is the order of reactivity from fastest to slowest in an SN2 reaction for the following substrates? a. t-butyl bromide b. isopropyl bromide c. neopentyl bromide d. ethyl bromide e. methyl bromide So far have methyl bromide> ethyl bromide> neopentyl

*asked on March 24, 2019* -
## math ; Geomentry

A Ferris wheel is drawn on a coordinate plane so that the first car is located at the point (40,0). What are the coordinates of the first car after a rotation of 270 degrees counterclockwise about the origin?

*asked on October 9, 2017* -
## Science

How many kilograms of water can be evaporated at 100 degrees Celsius by the combustion of 470 litres of fuel oil whose heat of combustion is 37 MJ/Litre

*asked on June 26, 2017* -
## physic..plz check if corrected

If the energy used to heat up a block of 2kg of copper is 115.8 kJ, what is the temperature it was heated to if the starting temperature was 100oC and the specific heat capacity is 386 J/kgK. E=MC(T2-T1) 115800=2*112.85(T2-100) 115800=225.7(T2-100)

*asked on June 4, 2017* -
## Calculus

Find the distance traveled by a particle with position (x, y) as t varies in the given time interval. x = cos^2 t, y = cos t, 0 ≤ t ≤ 9π and the length of the curve so far i got ∫0 to 9pi √((-2cos(t)sin(t))^2+(-sint)^2) I am having trouble

*asked on April 29, 2017* -
## Math - combinatorics/ permutations

There are nine differently-titled books on a shelf. Four books have red covers, while the other five have black covers. How many different arrangements of the books can there be, if (a) there are no restrictions on the order in which the books are placed?

*asked on April 29, 2017* -
## math

Ms. Handler walks to work at an average speed of 5 kilometers per hour. If she increases her speed to 6 kilometers per hour, she will save 10 minutes. Find the distance she walks.

*asked on October 12, 2015* -
## math

Tall versus Short All tall 787 tall 277 short Smooth versus Wrinkled Seeds All smooth seeds 5,474 smooth 1,850 wrinkled Yellow versus Green Seeds All yellow seeds 6,022 yellow 2,001 green From the table and the theoretical results answer questions 1 and 2.

*asked on April 2, 2015* -
## eng

what exactly does destiny mean and please don't tell me to google it because everytime i to, i keep getting confused. and also do u believe that destiny plays a role in our lives or no? and why?

*asked on November 27, 2014* -
## Math

Put in order from least to greatest: 0.748 11/16 76%

*asked on January 22, 2014* -
## math

Given ABCD with A = (1,1),B = (4, 2), C = (4, 5), and D = (1, 4),what are the coordinates for Point D' if the y-axis is the reflecting line?

*asked on August 16, 2013* -
## Algebra

Evaluate e^0.1 to four decimal places

*asked on February 8, 2013* -
## physics

A person pulls a toboggan for a distance of 34.6 m along the snow with a rope directed 29.3 ° above the snow. The tension in the rope is 110 N. (a) How much work is done on the toboggan by the tension force? (b) How much work is done if the same tension

*asked on October 4, 2012* -
## Physics

In this problem, your task is to analyze a lead balloon. The balloon in question is a hollow sphere of diameter of 20.0 m, constructed from a lead foil 0.25 mm thick and filled with helium gas. Below the balloon, a passenger basket is suspended. The mass

*asked on June 15, 2012* -
## math

What is the value of the output for the function, g(c) = 19 c2, if the input is 4?

*asked on March 1, 2012* -
## Physics

A mass of 2.2kg is placed on a stiff vertical spring which has a spring constant of 950n/m. The object is then pressed against the spring until it has been compressed a distance of 77cm. The mass is then released and is allowed to be thrown up into the

*asked on February 25, 2012* -
## general chem

Calculate the molarity of a solution made by dissolving 12.5 grams of Na2CrO4 in enough water to form exactly 550 mL of solution. (b) How many moles of KBr are present in 150 mL of a 0.275 M solution? (c) How many milliters of 6.1 M HCl solution are needed

*asked on October 9, 2011* -
## Physics

Tom Brady passes a football – at a velocity of 50 ft/s at an angle of 40 degrees to the horizontal – toward an intended receiver 30 yd straight downfield. The pass is released 5 ft above the ground. Assume that the receiver is stationary, is isolated

*asked on April 25, 2011* -
## Physics

f a water bed is 1.81 m on each vertical side and 30 cm high. Find its weight. The acceleration of gravity is 9.8 m/s2 and the density of water is 1000 kg/m3. Answer in units of N

*asked on April 15, 2011* -
## physics

An acorn and tree leaf fall from the same height and time. Which reaches the ground first and why?

*asked on April 9, 2011* -
## chemistry

AT 40 DEGREES HOW MUCH POTASSIUM CHLORIDE CAN BE DISSOLVED IN 300G OF WATER

*asked on January 20, 2011* -
## Microeconomics

Pharmaceutical drugs have an inelastic demand, and computers have an elastic demand. Suppose that technological advance doubles the supply of both products (that is, the quantity supplied at each price is twice what it was).

*asked on November 22, 2010* -
## Algebra

If the sides perpendicular to the wall have length x feet, which of the following (A, B, C, or D) represents the area A of the garden? A(x) = –2x2 + 30x A(x) = –2x2 + 60x A(x) = x2 – 60x A(x) = 2x2 – 60x

*asked on November 21, 2010* -
## physics

A heavy freight train has a mass of 11800 metric tons. If the locomotive can pull with a force of 691000 N, how long does it take to increase it's speed from 0 to 70.3 km/h?

*asked on October 31, 2010* -
## physics

A heavy freight train has a mass of 11800 metric tons. If the locomotive can pull with a force of 691000 N, how long does it take to increase it's speed from 0 to 70.3 km/h?

*asked on October 31, 2010* -
## Physics

A heavy freight train has a mass of 11800 metric tons. If the locomotive can pull with a force of 691000 N, how long does it take to increase it's speed from 0 to 70.3 km/h?

*asked on October 31, 2010* -
## Physics- 2D Collisions

nitially, mass one (2.10 kg) has a velocity of 5.90 m/s and mass two (2.80 kg) is at rest. After they collide, mass one emerges at an angle theta = 33.0 degrees. What is the speed of mass one after the collision if the collision is completely elastic?

*asked on March 29, 2011* -
## gen chem

what is the concentration of an aqueous solution when you add 9.58x10^-4 moles of copper nitrate to 42ml of water

*asked on October 17, 2010* -
## Business

Communist Prison Camp In such prisons the total regimen, consisting of physical privation, prolonged interrogation total isolation from former relationships and sources of information, detailed regimentation of all daily activities, and deliberate

*asked on October 15, 2010* -
## grammar

in the sentence "He felt hungry and thought about the lunch wrapped in his handkerchief." which are the linking verbs and which are the action verbs?

*asked on October 12, 2010* -
## algebra

the acme widget company has $13,000 available for making widgets. part of the money is spent on an advanced widget-bending machine costing $1,000. the manufacturing cost for each widget is $3. how many widgets can be made with the money available?

*asked on October 9, 2010* -
## algebra

find the domain of the function p(x) = x^2 - 2x + 10

*asked on July 8, 2010* -
## chemistry

The equation for burning C2H2 is 2C2H2(g) + 5O2(g) ⎯→ 4CO2(g) + 2H2O(g) a. If 15.9 L C2H2 react at STP, how many moles of CO2 are produced? (Hint: At STP, 1 mol = 22.41 L for any gas.) b. How many milliliters of CO2 (density = 1.977 g/L) can be made

*asked on June 2, 2010* -
## calculus

A particle moves along a straight line with equation of motion s = f(t), where s is measured in meters and t in seconds. Find the velocity and speed when t = 9. f(t) = t ^-1 - t

*asked on February 24, 2010* -
## american government

what two actions could congress take to undo a supreme court ruling that a federal law is unconstitutional? explain the advantages and disadvantages of each action?

*asked on January 21, 2010* -
## Econ

A result of welfare economics is that the equilibrium price of a product is considered to be the best price because it a. maximizes total revenue for firms and maximizes the quantity supplied of the product. b. maximizes the combined welfare of buyers and

*asked on March 30, 2009* -
## Math

For a period of time as an alligator grows, its mass is proportional to the cube of its length. When the alligator's length changes by 15.8%, its mass increases by 17.3kg. Find its mass at the end of this process.

*asked on August 19, 2008* -
## Science

Ions are electrically charged particles that are formed when certain compounds are dissolved in water. These solutions will conduct electricity. The Swedish scientist Svante Arrhenius coined the term ion (which means wanderer) to explain why solutions of

*asked on July 18, 2008* -
## HELP! ASAP! SPANISH!

i am writing a poem for spanish and in the poem we have to say a phrase about an animal. i have a crocodile. what is a good phrase that i can say in spanish about a croc? thanks sooo much!

*asked on May 18, 2008* -
## Physics

Explain how redioactive decay has always warmed the Earth from the inside and how nuclear fusion has always warmed the Earth from the outside.

*asked on April 25, 2008* -
## Physics

An electron and a proton are traveling at the same speed. Which one has the longer wavelength?

*asked on April 4, 2008* -
## languages

are there any free downloadable courses that I could teach myself Arabic with? I can't seem to find any good ones.

*asked on March 28, 2008* -
## Chem

Manganese dioxide reacts with bromide ions to form manganese ions and bromate ions in an acidic aqueous solution. Write the balanced equation for this reaction. 1)Br- + MnO2 + 3H2O --> Mn2+ + BrO3- + 2H3O+ 2)Br- + 3MnO2 + 6H3O+ ---> 3Mn2+ + 9H2O + BrO3-

*asked on December 12, 2007* -
## social studies

who does John Hancock resemble, and how?

*asked on September 30, 2007* -
## Physics

For a resonance tube apparatus (open ended on one side) with a total tube length of 1.00 meter, on a day when the speed of sound is 340 m/s, how many resonance positions will be observed as the piston position is varied for a frequency of 500 Hz? and 1000

*asked on July 1, 2007* -
## chem expirement!

You are required to design an experiment to test Hess's law using the combustion of ethanol. Write a brief design for this experiment. What I wrote as my answer: Hess’ Law: is the algebraic addition of chemical equations yields a net equation whose

*asked on May 17, 2007* -
## chem experiment:

You are required to design an experiment to test Hess's law using the combustion of ethanol. Write a brief design for this experiment. What I wrote as my answer: Hess’ Law: is the algebraic addition of chemical equations yields a net equation whose

*asked on May 17, 2007* -
## Organic Chemistry

What is the product formed from a reaction of butanal and sodium hydroxide? cyclopentanone and sodium hydroxide? acetophenone and sodium hydroxide? Thanks. You want to look up information about the Aldol condensation.

*asked on March 6, 2007* -
## organic chemistry

which alcohol and carboxylic acid would produce benzyl isobutyrate by Fischer esterification? and which alcohol and carboxylic acid would produce isobutyl benzoate by fischer esterification? I can't find anything about Fischer esterification specifically.

*asked on March 5, 2007* -
## fischer esterification

which alcohol and carboxylic acid would produce benzyl isobutyrate by Fischer esterification? and which alcohol and carboxylic acid would produce isobutyl benzoate by fischer esterification? Since this is not my area of expertise, I searched Google under

*asked on March 4, 2007* -
## chemistry-lab

2.What does it mean to “follow the course of a reaction”? I would imagine it means to find the overall order of the reaction and make it in to a rate law equation. That's part of it. It can mean, in addition, to knowing any intermediates formed and how

*asked on February 13, 2007* -
## Science

A supersonic jet flying at 145 m/s is accelerated uniformly at the rate of 23.1 m/s squared for 20.0 s. a. What is its final velocity? b. The speed of sound in air is 331 m/s. How many times the speed of sound is the plane's final speed? I don't care what

*asked on October 5, 2006* -
## Macroeconomics

The Big Mac Index is a numerical tool for assessing disparities in consumer purchasing power between countries. Suppose that the Big Mac costs 7.50 Canadian dollars in Canada and 5.50 US dollars in the US. Suppose that the nominal exchange rate is 1.2

*asked on March 24, 2020* -
## Economics

The Big Mac Index is a numerical tool for assessing disparities in consumer purchasing power between countries. Suppose that the Big Mac costs 7.50 Canadian dollars in Canada and 5.50 US dollars in the US. Suppose that the nominal exchange rate is 1.2

*asked on March 24, 2020* -
## math

Nico is saving money for his college education. He invests some money at 8%, and $1800 less than that amount at 5 %. The investments produced a total of $261 interest in 1 yr. How much did he invest at each rate?

*asked on January 21, 2020* -
## math

what is 1+2

*asked on August 22, 2019* -
## Chemistry

The major factor affecting why boron and hydrogen add across a double bond in an apparent anti-Markovnikov manner (i.e. H adds to the more substituted side) in hydroboration is

*asked on April 29, 2019* -
## Chemistry

For a π bond, p orbitals should be________ when they overlap. As a result, in the E2 mechanism, an _______ elimination is said to occur. I tried "p orbitals should be parallel when they overlap. As a result, in the E2 mechanism, an antiparallel

*asked on April 11, 2019* -
## Chemistry

Give the name or formula of a reagent other than sodium metal that will convert cyclopentanol to sodium cyclopentoxide.

*asked on April 1, 2019* -
## Chemistry

How do you find a step that has the largest rate constant in the forward reaction? When looking at a potential energy diagram

*asked on March 25, 2019* -
## Algebra Readiness

A right triangle is shown below. a=6 b=8 c=? The triangle is dilated by a scale factor of 2.5 to create a new triangle. What is the perimeter of the new triangle? answs; 120,24,60 and 150 i keep getting different answers can someone help?

*asked on November 30, 2018* -
## Math

A segemnt has endponits X(-6, 2) and Y(-1, -3). If D3/2 (XY) = (X’Y’), what are the coordinates of X’ and Y’? a. X’ (-7.5, 3.5) and Y’ (-2.5, -5.5) b. X’ (-4.5, 3.5) and Y’ (0.5, -1.5) c. X’ (-3, 1) and Y’ (-0.5, -1.5) d. X’ (-9, 3)

*asked on September 24, 2018* -
## physics

i dont know what the answer is... i got itwrong my answer was 1.78. whats the correct answer? A 57kg trampoline artist jumps vertically upward from the top of a platform with a speed of 4.7m/s. How fast is he going as he lands on the trampoline 3.8m below?

*asked on May 16, 2018* -
## Math - 3d points

submarine A starts at (1000x,0y,0z) goes towards (0x,100y,1000z). It travels 72km/hour = 20m/sec. If submarine B travels at the exact same speed, what should its starting point be to reach (0x,0y,1000z) at the exact same time submarine A reaches

*asked on April 22, 2018* -
## Math

I swam 10 cycles in 13.5 seconds what is my stroke rate?

*asked on February 15, 2018* -
## physics

A ball is dropped from a cliff and 2 seconds later, a second ball is thrown vertically downward. What must be the initial velocity of the second ball if it overtakes the first ball as it passes 400m ?

*asked on July 26, 2017*