Friday

January 20, 2017
Total # Posts: 318

**Chemistry**

Adding water to some chemicals can be dangerous because large amounts of heat are liberated. Which of the following does NOT liberate heat when water is added to it? KNO3 (the answer) NaOH Na CaO H2SO4 I guessed Na simply because it's the only one that's an element, ...

*May 2, 2012*

**Chemistry**

I think I get it, but just to clarify... Because we have a power supply, we know we have an electrolytic cell, which needs energy from an external source. For electrolytic cells, cathodes are considered the negative electrodes. If K+ and H20 go to the cathode, they get reduced...

*May 1, 2012*

**Chemistry**

A direct-current power supply of low voltage (less than 10 volts) has lost the markings that indicate which output terminal is positive and which is negative. A chemist suggests that the power supply terminals be connected to a pair of platinum electrodes that dip into 0.1-...

*May 1, 2012*

**Chemistry**

A 0.5224g sample of an unknown monoprotic acid was titrated with 0.0998M of NaOH. The equivalence point of the titration occurs at 23.82 mL. Determine the molar mass of the unknown acid.

*April 29, 2012*

**chemistry**

Hi Dr. Bob! I actually cleared it all up, but thank you!

*April 19, 2012*

**chemistry**

Hello, I have data here: tube # Contents Initial color (after 2 drops of universal indicator) Color after adding HCl Color after adding NaOH (after the HCl had been poured) 1 CO32-/HCO3- Dark purple Purple Purple 2 CO32-/HCO3- Dark purple -- -- 3 HCH3CO2/C H3CO2- red Light red...

*April 19, 2012*

**Chemistry**

Thanks so much! I get it now!

*April 10, 2012*

**Chemistry**

Hi Dr. Bob, When I do that, I get 11.30 as the pH, although I don't think that's it. Did I miss something?

*April 10, 2012*

**Chemistry**

HOBr (aq) <----> H+ (aq) + OBr- (aq), Ka = 2.3 x 10^-9 Hypobromous acid, HOBr, is a weak acid that dissociates in water, as represented by the equation. (a) Calculate the value of [H+] in a solution of HOBr that has a pH of 4.95. Ans: 1.1 * 10^-5 M (b) Write the ...

*April 10, 2012*

**Physics**

1800 N/C

*March 29, 2012*

**Math**

Help with identify the property 45x6=(40+5)x(5+6)= I think Assoiative prop. ( is this correct?) 6x1=6 I put identity prop. of 1 4+(6+5)=(4+6)+5= distributive prop. 8+(-8)=0 I put identity prop. of 0 5x4=4x5 I put communtive property Can you tell me if I have them correct? Thanks

*March 28, 2012*

**math**

A sample survey of 50 people in Harrisburg, PA indicates that 10 of them know the mayors name in the neighboring city. Out of 5,500 Harrisburg residents, how many would you predict know the name of the mayor of the neighboring city? I thought 1100. I did 10/50=x/5500, is this ...

*March 28, 2012*

**physics**

A spherical conductor has a radius of 14.0 cm and charge of 26.0 µC. Calculate the electric field and the electric potential (a) r = 10.0 cm, (b) r = 20.0 cm, and (c) r = 14.0 cm from the center. how do i calculate k?

*February 7, 2012*

**physics HELP MEEE SO CONFUSED**

A spherical conductor has a radius of 14.0 cm and charge of 26.0 µC. Calculate the electric field and the electric potential (a) r = 10.0 cm, (b) r = 20.0 cm, and (c) r = 14.0 cm from the center.

*February 7, 2012*

**Physics**

I have to create a teaching aid for physics based on the principles i have learnt like gravitation , mechanical properties and many more. I am not able to find the right experiment to demonstrate infront of my teacher.Please help me deal with this by providing information ...

*January 26, 2012*

**Physics**

I have to create a teaching aid for physics based on the principles i have learnt like gravitation , mechanical properties and many more. I am not able to find the right experiment to demonstrate infront of my teacher.Please help me deal with this by providing information ...

*January 25, 2012*

**Act Question**

all distances are in feet and all are right angles. a straight line drawn from point w to point z would be how long in feet?

*January 7, 2012*

**business**

For this question, use the information for Sports Baseballs, Inc. Sports Baseballs, Inc. is a corporation that manufacturers and sells baseballs across several states in the Southeast. It had sales of $2.7 million during the last year. Expenses were as follows: Cost of goods ...

*January 7, 2012*

**Math**

how can you break apart arrays when you multiply by 3?

*January 5, 2012*

**chemistry**

If you filled three balloons with eaqual volumes of hydrogen, argon, and carbon dioxide gas all at the same temperature and pressure, which ballon would weigh the most? The least?

*December 13, 2011*

**chemistry**

What mass of hydrogen peroxide should result when 1.50g of barium peroxide is reacted with 25.0mL of 0.50 M hydrochloric acid?

*December 13, 2011*

**chemistry**

a better understanding of how she got the answer

*December 13, 2011*

**chemistry**

Jenny please show me in better detail the set up of the answer.

*December 13, 2011*

**chemistry**

If you make a solution by dissolving 25.0g of sodium chloride in 100.0 mL of water. What is the boiling point of the solution?

*December 13, 2011*

**math**

A woman is sitting in a boat at anchor on a lake. Her boat bobs up and down once every 2.0·s. She notices that when the front of her 3.0·m long boat is at one wave crest, a second crest is at the middle of her boat, and a third is at the end. What is the ...

*December 8, 2011*

**science**

Observed under magenta colored lights, you see a crayon that appears red. What colors could the crayon be when observed under ordinary white lights? _____cyan ____magenta ____green ____yellow ____red ___black ___white ____blue

*December 8, 2011*

**chemistry**

A 30.0 mL sample of phosphoric acid is titrated with 18.0 mL of 3.0 M NaOH solution. What is the molarity of the phosphoric acid?

*December 7, 2011*

**PHYSICS HELP MEEE SO CONFUSED**

oops its 1 kg

*December 5, 2011*

**PHYSICS HELP MEEE SO CONFUSED**

Liam fires a bullet into a block suspended by two cables, embedding the bullet in the block. The mass of the bullet is 5g and the mass of the block is 1g. 1) If the maximum height of the block is ,h, is 35 cm, how fast was the bullet originally moving? (can you explain the ...

*December 5, 2011*

**Calculus**

I need help finding the derivative of this function: f(x)=(X^2+2)^4/5 Thanks in advance! Any help would be greatly appreciated!

*November 20, 2011*

**Grade 12- Advanced Funtions**

what about this question: Determine the roots algebraically by factoring. a) x^3-8x^2-3x+90=0

*October 13, 2011*

**Grade 12 Advanced Functions**

what about this question: Determine the roots algebraically by factoring. a) x^3-8x^2-3x+90=0

*October 13, 2011*

**math**

How to do polynaimals in 5th grade in the easyest form. How do you do problems like X+6=10 using all the steps instead of just Oh i now its 4

*September 28, 2011*

**Math**

I have posted the question again.. sorry it was "using L and w" A printed page is to have a total area of 100 square inches. The top and bottom margins are to be 1 inch and the side margins to be 1.5 inches. Let l represent the total length of the page and w ...

*September 27, 2011*

**Math**

A printed page is to have a total area of 100 square inches. The top and bottom margins are to be 1 inch and the side margins to be 1.5 inches. Let l represent the total length of the page and w represent the total width of the page. a) Write an equation, using and , to ...

*September 27, 2011*

**Math**

A printed page is to have a total area of 100 square inches. The top and bottom margins are to be 1 inch and the side margins to be 1.5 inches. Let l represent the total length of the page and w represent the total width of the page. a) Write an equation, using and , to ...

*September 27, 2011*

**Calculus**

How would you factor this? f(x)=x^3-2x^2-4x-4

*September 6, 2011*

**Epidemiology**

Identify the study design best described by the scenarios or research questions presented below. Provide a two-sentence rationale for your answer. Choose from: • Ecologic • Cross-sectional • Case-control • Retrospective (Historical) Cohort • ...

*August 8, 2011*

**health**

like u ate at 12 so when can you eat tuna next

*June 20, 2011*

**health**

when can you eat tuna after you ate egg?

*June 20, 2011*

**physics**

Thanks, my book provides the answer as 21.2 m/sec, I calculated the vertical component 28sin37=16.85 but since it did not match the correct answer I thought I needed another step. There has to be because your answer isn't even a choice.

*June 11, 2011*

**physics**

Determine the vertical component of a baseball's velocity if the ball is thrown at 28 m/sec at an angle of 37 degrees with the horizontal. The answer is 21.2 m/sec but I have no clue on how to solve this problem.

*June 11, 2011*

**Statistics**

please help

*May 5, 2011*

**Statistics**

jenny is 5'10" tall. the heights of the girls in the school are approximately normally distributed with a mean of 5'5" and a standard deviation of 2.6". What is the percentile of jenny's height?

*May 5, 2011*

**calculus**

The function f is twice differentiable, and the graph of f has no points of inflection. If f(6)+3, f'(6)=-1/2, and f"(6)=-2, which of th following could be the value of f(7). A.)2 B.)2.5 C.)2.9 D.)3 E.)4 the answer is A. but what are the steps to reach this answer?

*April 26, 2011*

**calculus**

The sides and diagonal of the rectangle above are strictly increasing with time. At the instant when x=4 and y=3, dx/dt=dz/dt and dy/dt=k(dz/dt). What is the value of k at that instant. solved for z with pythagorean theorem and stuck at that step. z=5

*April 26, 2011*

**statistics**

A professor knows that in her class 37% of the students have passed an Algebra course, 29% have passed an English course, and 21% have passed both courses. If one student is selected at random from this class, find the probability that: c) the student did not pass algebra.

*April 24, 2011*

**math**

A professor knows that in her class 37% of the students have passed an Algebra course, 29% have passed an English course, and 21% have passed both courses. If one student is selected at random from this class, find the probability that:

*April 24, 2011*

**statistics**

a) are the outcomes on the two cards independent? why? b) find P(3 on 1st card and 10 on 2nd) c) find P(10 on 1st card and 3 on 2nd) d) find the probability of drawing a 10 and a 3 in either order.

*April 15, 2011*

**statistics**

you draw two cards from a standard deck of 52 cards, but before you draw the second card, you put the first one back and reshuffle the deck.

*April 15, 2011*

**vectors and physics**

A 40 kg weight is suspended at P which is held up By the ropes PQ and PR the ropes make angles at 160 degrees and 130 degrees respectively with the vertical, find the tension in the ropes

*April 13, 2011*

**algebra**

How to solve for the unknown: 2/3/10 = 1.8/r

*April 12, 2011*

**biology**

if a man is a hetero zygote for a trait but the woman is homozygous recessive, what are the chances that their children will be homozygous dominant

*April 11, 2011*

**algebra**

(2x(tothe2ndpower)-3x+4)-(3x(tothe2ndpower)-x+2= ????

*February 4, 2011*

**math (perimeter)**

i need to find the perimeter of a triangle with the demensions : 2(q^2-3q) , q+10 , and q^2 .

*January 23, 2011*

**physics**

A particle travels horizontally between two parallel walls separated by 18.4m. It moves towards the opposing wall at a constant rate of 7.2m/s. Also, it has an acceleration in the direction parallel to the walls of 2 m/s^2. a) What will its speed be when it hits the wall? b) ...

*December 29, 2010*

**physics**

THANK YOU!!!

*December 29, 2010*

**computers**

What ideas can you propose for the future of processor design? What do you think the limit of clock speed for a processor will be? How could a CPU communicate more quickly with memory? What could future cache designs look like? I've been looking in Google search, Google ...

*December 13, 2010*

**math(trig)**

1) What's the linear velocity of a point on the tip of a 6-ft propeller turning at 1200 revolutions per min? 2) A gear is driven by a chain that travels 90m/min. Find the radius of the gear if it makes 50 revolutions per minute.

*December 6, 2010*

**math(trig)**

1) A 6-ft propeller turns at 1200 revolutions per minute. Compare the angular velocity of the tip with the angular velocity at a point 10 in. from its center. 2) What is the angular velocity of a point on the tread of a 15-in. diameter tire on a car traveling 55 mph?

*December 6, 2010*

**Chemistry Cell notations**

also shouldn't it be the coefficient of H^+ in the second equation be 14?

*December 2, 2010*

**Chemistry Cell notations**

Okay so the problem I had with this is like...I did't understand that when it was written say on the left of the double vertical line how you know H2O --> O2 + H+ will it always be written in the order of how you write the reaction? or like could you also right it like ...

*December 2, 2010*

**Chemistry Cell notations**

Enter the balanced chemical equation including states that describes the electrochemical cell that is represented by the cell notation as shown. Pt(s) l H2O(l) l O2(g) l H+(aq) ll H+(aq), Cr2O72-(aq), Cr3+(aq) l Pt(s)

*December 2, 2010*

**math**

The 2 pulleys in the figure have radii of 15 cm and 8 cm, respectively. The larger pulley rotates 25 times in 36 seconds find the angular velocity of each pulley in radians per second. Find angular velocity of each pulley in radians per second.

*December 2, 2010*

**math**

find v for the following question.. the tip of the airplane propeller 3m long, rotating 500 times per minute (hint r=1.5m)

*December 2, 2010*

**chemistry half reactions**

How do i solve this half reaction with Mg(OH)2(s) --> Mg(s)? Complete and balance the displayed half reaction in basic aqueous solution taking into account the electrons. Mg(OH)2(s) → Mg(s)

*November 23, 2010*

**physics**

Sprinting near the end of a race, a runner with a mass of 70 kg accelerates from a speed of 6 m/s to a speed of 9 m/s in 2 s. (a) What is the runner's average acceleration during this time? (b) To gain speed the runner produces a backward force on the ground, so that the ...

*November 22, 2010*

**physics**

1. How much acceleration does a 747 jumbo jet of mass 31600 kg experience in takeoff when the thrust for each of four engines is 30000 N? 2. Two boxes are seen to accelerate at the same rate when a force F is applied to the first and 5F is applied to second. What is the mass ...

*November 22, 2010*

**Physics**

A bullet of mass 5.15 g is fired horizontally into a 2.74 kg wooden block at rest on a horizontal surface. The coefficient of kinetic friction between block and surface is 0.185. The bullet comes to rest in the block, which moves 1.84 m. (a) What is the speed of the block ...

*November 21, 2010*

**physics**

What is the acceleration of a 23 kg pail of cement that is pulled upward (not sideways!) with a force of 300 N?

*November 21, 2010*

**chemistry**

If 0.0490 mol of solid CaCO3 and 380 mL of 0.135 M aqueous H2SO4 are reacted, what volume (L) of gaseous CO2 measured at 1.1 atm pressure and 301 K is produced. H2SO4(aq) + CaCO3(s) → CO2(g) + CaSO4(s) + H2O(l)

*November 21, 2010*

**Limiting reagent**

If 270. mL of 0.08089 M aqueous Pb(NO3)2 and 710. mL of 0.05493 M aqueous Na+ are reacted stoichiometrically according to the equation, what mass (g) of Na+ remained? Pb(NO3)2(aq) + 2 NaI(aq) → PbI2(s) + 2 NaNO3(aq)

*November 21, 2010*

**Reaction rates**

oooh, righteous! Thanks so much I appreciate the time you take out to help!

*November 20, 2010*

**Reaction rates**

so... k=Ae^(Ea/RT) Do I set it up as ratios? I.e. 0.0000100s-1=Ae^(-Ea/R * 636) ____________________________ 0.000479s-1=Ae^(-Ea/R * 700) A cancels out ...and then solve from there?

*November 20, 2010*

**Reaction rates**

The reaction, C2H5Br --> C2H4 + HBr, has a rate constant k = 0.0000100 s-1 at 363 °C and k = 0.000479 s-1 at 427 °C. What is the rate constant for the reaction at 725 K? Round your answer to 3 significant figures.

*November 20, 2010*

**Concentration and Reaction**

The rate of the following reaction: Radioactive decay of 90Sr, is characterized by the rate constant k = 0.024 year-1. What is the half-life (in years) for this reaction at the same conditions when the initial concentrations are 0.0356 M? (Round your answer to 3 significant ...

*November 20, 2010*

**chemistry**

What is the rate of the following reaction (M/s) if the rate constant for the reaction is 0.500 L•mol-1•s-1 and the concentration of each reactant is 0.0628 M. (The units for the rate constant depend upon the rate law). CO + NO2 --> CO2 + NO

*November 20, 2010*

**social studies**

How do elections in a single-member district differ from elections in states that fill their seats at-large?

*November 20, 2010*

**chemistry**

If 380. mL of 0.4294 M aqueous CaBr2 and 250. mL of 0.5880 M aqueous SO42- are reacted stoichiometrically according to the equation, how many mol of CaBr2 remained? Al2(SO4)3(aq) + 3 CaBr2(aq) → 2 AlBr3(aq) + 3 CaSO4(s) ----------------------------------------- If 270. ...

*November 17, 2010*

**BIOLOGY GR.12**

What are the differnt conditions for yest fermentation. i have to make a hypothesis and experment based on yeast fermentation. I WANT TO KNOW WHAT EFFECTS THE FERMENTATION. for example using a higher temp to put my yeast in will make the fermentation faster. WHAT OTHER FACTORS...

*October 20, 2010*

**chemistry**

Also other information Answer they gave: 0.000148571182 Molsr Mass: PbSO4 303.26

*October 16, 2010*

**chemistry**

What about this question? Calculate the mass (g) of PbSO4 that will dissolve in 2000 mL of 0.0694 M K2SO4 solution. The equation represents the solubility process. PbSO4 (s) Pb2+ (aq) + SO42- (aq) Ksp = 1.7 x 10-8

*October 16, 2010*

**chemistry**

the standard state free energy of hydrolysis of acetyl phosphat is G= -42.3 kJ/mol. Calculate the free energy change for the acetyl phosphate hydrolysis in a solution of 2mM acetate, 2 mM phospate and 3 nM acetyl phospahte.

*October 6, 2010*

**Chemistry**

An enzymatic hydrolysis of fructose was allowed to proceed to equilibrium at 25 degrees C. The original concentration of fructose-1-p was .2 M, but when the system had reached equlibrium the concentration of fructose 1-p was only 6.52 * 10 -5 M. Calculate the equilibrium ...

*October 6, 2010*

**physics**

If there were no air drag, how fast would drops fall from a cloud 2.4 kilometer above the Earth's surface? answer in m/s.

*October 6, 2010*

**physics**

If there were no air drag, how fast would drops fall from a cloud 2.4 kilometer above the Earth's surface? Answer in m/s.

*October 5, 2010*

**physics**

I think it's the wrong answer because I plugged it in and it was still marked wrong.

*October 5, 2010*

**physics**

What is the acceleration of a vehicle that changes its velocity from 120 km/h to a dead stop in 7 s? Answer in km/h·s

*October 5, 2010*

**Statistics**

P(10 on 1st card and 3 on 2nd)

*September 26, 2010*

**math**

find the other endpoint (x,11) of a segment given the endpoint (5,-4) and a distance of 17.

*September 21, 2010*

**math**

find the domain & range of each relation & identify any relations that define functions y=3(x+1)^2-5

*September 15, 2010*

**physics**

Bertrand Russell wrote, "I think we must retain the belief that scientific knowledge is one of the glories of man. I will not maintain that knowledge can never do harm. I think such general propositions can almost always be refuted by well-chosen examples. What I will ...

*September 12, 2010*

**physics**

1. What is a typical drift speed of electrons that make up a current in a typical DC circuit? (zero, less than 1 cm/s, about 10 m/s, or the speed of light) 2. What is the typical drift speed in a typical AC circuit? (zero, less than 1 cm/s, about 10 m/s, or the speed of light)

*July 16, 2010*

**physics**

1. If the voltage impressed across a circuit is constant but the resistance increases by a factor of 15. By what factor does the current change? 2. If the resistance of a circuit remains constant while the voltage across the circuit decreases by a factor of 12, by what factor ...

*July 16, 2010*

**physics**

1. How much does it cost to operate a 75 W lamp continuously for 1 week if the power utility rate is 7/kWh?

*July 16, 2010*

**physics**

1. (a) How far below an initial straight-line path will a projectile fall in eight seconds? (b) Does your answer depend on the angle of launch or on the initial speed of the projectile? the answer is no. but defend it. 2. Why is it important that a satellite be above Earth'...

*July 13, 2010*

**physics**

1. What did Newton conclude about the force that pulls apples to the ground and the force that holds the moon in orbit? 2. What does the very small value of the gravitational constant G (in standard units) tell us about the strength of gravitational forces? 3. We can think of ...

*July 13, 2010*

**physics**

1. If our sun shrank in size to become a black hole, using the gravitational force equation, explain why the Earth's orbit would not be affected. 2. Strictly speaking, you weigh a tiny bit less when you are in the lobby of a massive skyscraper than you do at home. Why is ...

*July 13, 2010*

**physics**

1)A toy train is initially at rest on a track fastened to a bicycle wheel, which is free to rotate. How does the wheel respond when the train moves clockwise? When the train backs up? Does the angular momentum of the wheel-train system change during these maneuvers? How would ...

*July 9, 2010*

**Finance**

How long would it take to accumulate $2,000,000 at a rate of 5% with the starting amount of $1,150,

*May 31, 2010*