Tuesday

July 29, 2014

July 29, 2014

Total # Posts: 741

**chemistry**

A block of copper of unknown mass has an initial temperature of 66.7 ∘ C . The copper is immersed in a beaker containing 95.5g of water at 20.6 ∘ C . When the two substances reach thermal equilibrium, the final temperature is 26.0 ∘ C .What is the mass of the...

**math**

At Dora's donut shop, dora makes 15 different varieties of donuts. Seven of these varieties are filled with jelly or cream. Officer sweetooth was sent to dora's shop to choose a dozen donuts, all different, with six filled and six unfilled. How many different assortmen...

**math **

Indicate whether the following statement is true or false. If a figure can be translated, then it will tessellate. I say false am I right?

**physics**

an electron in the second energy level absorbs a photon of energy 6 ev what's the speed of the ejected electron? I have tried to manipulate and use the kinetic energy equation, c= lamba x f, and many other ways, but I don't know why can't get the answer, which is v...

**math**

Use integers from-3 to 3 to graph the equation. y=1/3|x|-2. Please help me how it would be on a graph

**math**

I forgot to put use the integers -3 to 3 to graph the equation.

**math**

What would a graph look like with the equation y=-2(x)2+3.the two next to the x means to the second power. Please help me

**math**

Your description helped me understand thank you. It is D

**math**

Is it A

**math**

The vertices of ABC are A(2,-5), B(-3,5), and C(3,-3).the triangle is reflected over the x-axis.use arrow notations to describe the original triangle and its reelection. A) A(2,-5),B(-3,5),C(3,-3)->(2,-5),(-3,5),(3,-3) B) A(2,-5),B(-3,5),C(3,-3)->(-2,5),(3,-5),(-3,3) C) ...

**math**

Can't you just tell me if its a,b,c, or d? I'm stressed out please

**math**

The point C(3,-1) is translated to the left 4 units and up 1 unit.write a rule to describe the translation.what are the coordinates of the image point? A) (x,y)->(x+4,y+1);(7,-2) B) (x,y)->(x-4,y-1);(-1,0) C) (x,y)->(x+4,y-1);(7,0) D) (x,y)->(x-4,y+1);(-1,0) Is it d

**math**

what is the correct description for the translation of A to A? A(10,3)->A(1,6) a) right 9; up 3 b) left 9; down 3 c) right 9; down 3 d) left 9; up 3 Is it C

**math**

y=1/3|x|-2 use integer values of x from-3 to 3 to graph the equation. Please help me graph this

**math**

y= -2x+3.the x has a 2 above it

**math**

I'm only in seventh grade and I don't understand any of this.what does a parabola look like

**math**

y=2x^+3 use integer values of x from -3 to 3 to graph the equation. Someone please tell me how to graph this

**Alg**

order your answers from smallest to largest x, then from smallest to largest y. If there is no solution, enter NO Solution 2x^2+3y^2=48 x^2-y^2=4 (x,y)= ( , ) (, ) (x,y)= ( , ) (, ) (x,y)= ( , ) (, ) (x,y)= ( , ) (, )

**statistics**

Data were collected on 100 students regarding their class and major. The data are summarized in the following contingency table. What is the probability of randomly selecting a sophomore or an undeclared student?

**Alg**

A car with good tread can stop in less distance than a car with poor tread. A model for the stopping distance d, in feet, of a car with good tread on dry cement is d = 0.04v2 + 0.5v, where v is the speed of the car in miles per hour. If the driver must be able to stop within 6...

**graphing**

(0,-2)is the vertex- what is the domain and range??? State the domain and range of the function. (Enter your answers using interval notation.)

**Intermediate algebra**

Can you show the work of how to work this word problem ? A local electronics store will sell 7 ax adapters and 2 rechargeable flashlights for $86 or 3 ac adapters and 4 rechargeable flashlights for $84. What is the price of a single ax adapter and a single rechargeable flashli...

**Chem; States of Matter**

Thanks! My book suggests that: Steam = [[(175)(4.18)(100)] /1000] + 175(1mol/18.015)(-40.7/1mol) Where -40.7 is the Hvap ... I think. So I'm still super lost with that one weird extra step! Everything else is the same!

**Chem; States of Matter**

To an insulated container with 100.0 g H2O (l) at 20.0 degrees C, 175 g steam at 100.0 degrees C and 1.65 kg of ice at 0.0 degrees C are added. a) What mass of ice remains unmelted after equilibrium is reached? b) what additional mass of steam should be introduced into the ins...

**Chemistry**

For example, when a question asks about two equivalents of bromine, does that mean Br2 OR 2Br2? Thanks

**Chemistry**

Thanks :) so just to be clear, does it matter what the Mg is reacting with, or is it always going to have the coating of the MgO on it?

**Chemistry**

When a student doesn't polish a sample of Mg ribbon before massing it, what happens when calculating the molar volume? Is it that the Mg ribbon doesn't completely react therefore less volumes of gas are produced?

**Chemistry**

How would you define pressure in the unit of thermodynamics? Is it just a force basically?

**physics**

I think it would just be Fg x m, so 70kg times 9.81 m/s^2, and then multiply all of that by 2.9m, and the negative is just saying what direction the man is falling, meaning downwards

**BUSINESS**

Do you believe economic principles like competition apply in both private and public organizations? Why?

**Science**

suppose that a population of skunks lives on an isolated island is 500 skunks are present today and the birth rate is 65 per week and the death is 47 per week how many skunks to you predict will be on the island 105 days from now and what would a graph population versus time l...

**chemistry**

ok, so i did a lab called: measurements using electrochemical cels and electroplating, and one of the post lab questions asks,if the student fails to dry the electrode, in this case (Cu+2), what effect does it have on the calculated value of Faraday? and what affect does it ha...

**Chemistry**

how can you tell if something with oxidize or reduce some other thing, based on the standard reduction potential table?

**Chemistry**

how can you tell if something with oxidize or reduce some other thing, based on the standard reduction potential table?

**Chemistry(DrBob222)**

thanks for your help :)

**Chemistry(DrBob222)**

the procedure is no more precise really, I understand the lab, if i can ask a different question then, when delta g is negative and becoming less negative (or more positive), why is this happening over a decrease in temperature (increase in volume)

**Chemistry(DrBob222)**

yes I understand, and this helps a lot, but what I don't understand, is why in one trial the delta s was higher than in another trial, could you explain why that happened?

**Chemistry(DrBob222)**

it went back up to 116.4*

**Chemistry(DrBob222)**

So, i did this lab, a solubility and thermodynamics lab of KNO3, and in it we had to determine the delta h delta g and delta s, the question i have is what is the relationship of the signs delta h, delta s, and delta g, to the dissociation of the salt and the temperature chang...

**Chemistry(DrBob222)**

for a thermodynamics lab, I have to graph the ln K vs. 1/T, so does the ln K go on the y-axis and the 1/T go on the x-axis?

**AP Chemistry**

for a thermodynamics lab, I have to graph the ln K vs. 1/T, so does the ln K go on the y-axis and the 1/T go on the x-axis?

**Physics help please**

A crate is dragged 5.0 along a rough floor with a constant velocity by a worker applying a force of 125N to a rope at an angle of 30degrees to the horizontal. Calculate the work done by the tension in the rope, the force of friction, and the net force. I know the work don on t...

**Chemistry (DrBob222)**

Is the relationship between delta G and Temperature inverse or direct?

**AP US History**

When the south Carolina seceded in 1860 they seceded because Abe Lincoln was elected president. But, is the secession of South Carolina also an example of state's rights? if so, how?

**physics**

A 70.5kg football player is gliding across very smooth ice at 2.05m/s . He throws a 0.470kg football straight forward. What is the player's speed afterward if the ball is thrown at 14.5m/s relative to the ground? What is the player's speed afterward if the ball is thro...

**chemistry (Dr.Bob222)**

Ok, so when doing a serial dilution, would you day that the first well with no ppt represents a perfectly saturated solution, why or why not?

**chemistry (Dr.Bob222)**

Do serial dilutions start out as saturated solutions?, Meaning when it starts out ppt forms, but there is a point where ppt stops forming, so when the ppt stops forming does that mean it is representing a saturated solution, and that when the ppt is not forming the solution ha...

**Physics**

A fire truck attaches two fire hoses to a hydrant to fight a fire. Each hose has a diameter of 20 cm. The underground water pipe going to the hydrant has a diameter of 100 cm. In the underground pipe, the water has a speed of 2.0 m/s.

**Please help!- Physics**

i dont get it

**Chemistry(Dr.Bob222)**

Does the [H+]=[OH-] at the midpoint or the equivalence point?

**Chemistry(Dr.Bob222)**

What does it mean for something do to be neutralized? Is that when the [H+]=[OH-]? or is that totally wrong?

**History Quote**

“Man is not made better by being degraded; he is seldom restrained from crime by harsh measures, except the principle of fear predominates in his character; and then he is never made radically better for its influence.” - Dorothea Dix What exactly does this quote mean?

**Algebra**

Remove the parentheses from the following expression, and combine like terms: 3(ax + b2 – c) + 2 22 A. –3(ax – b2 + 3c – 6 B. 3ax +3b2 – 3c + 2 C. 3(ax + 3b2 – 3c + 6 D. (ax + b2 – c + 5

**Math**

What is a 2 step equation that equals 8 ?

**Chemistry (Dr.Bob222)**

Ok thanks, yes that answer was right, thanks so much for explaining the equation to me, it makes total sense now!

**Chemistry (Dr.Bob222)**

Just Kidding I got 46.51, but that is not one of the answer choices, so which would I pick? or did I do it wrong?

**Chemistry (Dr.Bob222)**

ok, so I got 3.32, so would I just multiply that by the half-life? Because the answer choices are 28 days, 14 days, 42 days, 56 days, and 70 days

**Chemistry (Dr.Bob222)**

The half-life of P-32 is 14 days. How long after a sample is delivered can a laboratory wait to use a sample in an experiment if they need at least 10 percent of the original radioactivity? I need help on how to set up this problem. What is the general equation to use for a ha...

**Chemistry (Dr.Bob222)**

How can you tell if a salt is neutral? Like the examples you gave: NaCl, KCl and KNO3, how do you know their anions or cations won't hydrolyze

**Chemistry (Dr.Bob222)**

The generic equation: Base− + H2O -> HBase+ OH− can be used to account for the pH of which salt? 1)CaI2 2)NH3 3)KCN 4)Al(NO3)3 5)NaCl Ok, so I know NH3, won't work because it is not a salt. The answer is KCN, but I don't understand why, could you explain...

**Chemistry (Dr. Bob222)**

How can you tell if something is highly concentrated or lowly concentrated? For example: H2CO3, H+, HCO3-, CO3(2- charge), is in order of highest concentration to lowest concentration, can you explain why it is that order? Thanks for your help :)

**physics**

A flower pot is thrown out of a window with a horizontal velocity of 8 m/s. If the window is 1.5 m off the ground, how far from the window does it land?

**Chemistry**

Hello Dr. Bob, I'm also having issues with a similar problem. I was able to calculate the XAr, but am unable to find the correct answers for H2 and N2, can you please help this Blake kid and I out? My book shows no problems of this sort, in order for me to work out and i&#...

**Chemistry help (DrBob222)**

ok will do, I just honestly had no idea how to do this. Can you explain how you got "2012 kJ/5*32 g oxygen. Therefore, for 320 g (10*32 g O2) you will get (2012 kJ/160) x 320 = ? " this part? thanks :)I don't understand where the grams came from, like I know it i...

**Chemistry help (DrBob222)**

propane (c3h8) is burned in oxygen to produce carbon dioxide and water. The heat of combustion of propane is -2012 kJ/mole. How much heat is given off when 3.0 mol C3H8 are react with 10.0 mol O2? Thanks, and please if possible show all steps!

**algebra**

-48x^3 + 32x^2 -8x

**chemistry (DrBob222)**

A student fails to fill the cuvette 2/3 full with the reaction mixture ( CV+ and OH-). What effect does this error have on the measured absorbance values? Thank you :)

**chemistry (Dr.Bob222)**

In a reaction, if the concentration decreases faster, that means the reaction has a larger rate constant, and a faster reaction, and a shorter half-life. Is that a correct statement? If not, please correct me, thanks for your help :)

**Physics Changing Acceleration **

Derive position, velocity, and acceleration kinematics equations for an object undergoing a changing acceleration? I understand that somehow we need to get (∆a/∆t) as the change in acceleration into the kinematic equations but I really don't know where to start.

**Physics (pls help mr.bobpursley or drbob222)**

A block is resting on top of a rough incline with coefficients of kinetic and static friction of 0.25 and 0.45 respectively. The angle of the incline is gradually increased until the block just begins to slip. How long will it take the block to slide to the bottom of the incli...

**chemistry**

We have to mixed 2 hydrated compounds each in a separate beaker filled with water, and then dump one of the solutions into the other and mix that, then filter the 1 solution out, so that the precipitate is caught in a filter paper, and the water is caught in an erlynmeyer flas...

**chemistry**

So I did an experiment at school in which we had to form 2.00 grams of precipitate by mixing 2 hydrated compounds. So for the products, obviously one of it is water, and the other 2 products are compounds, one of which, is insoluble. So when I measured the amount of precipitat...

**chemistry**

Oh! That makes much more sense, so the chemical factor is used to keep the atom of interest equal, which in this case was the Fe, and when we look at the atom of interest we don't need to worry about the rest of the formula being balanced, meaning in the example, as long a...

**chemistry**

So the bottom line is, that the chemical factor is used to make the amount of atoms equal?

**chemistry**

So when you wrote the balanced equation, how did you know that you had to add O2 in the equation? Thanks, sorry for the trouble

**chemistry**

Why is the molar mass of Fe3O4 being multiplied by 2? and why is the molar mass for Fe2O3 being multiplied by 3? Thanks

**chemistry**

An ore contains Fe3O4 and no other iron. The iron in a 38.9-gram sample of the ore is all converted by a series of chemical reactions to Fe2O3. The mass of Fe2O3 is measured to be 12.5 g. What was the mass of Fe3O4 in the sample of ore? Please show all work, not just the answe...

**chemistry**

Haha ok, thanks :)

**chemistry**

Isn't it 2 moles of KCL, from the balanced equation? for the 2nd step (mole ratio)

**chemistry**

A 1.24 gram sample of potassium chlorate was heated with manganese dioxide until no addition reaction was visible. THe potassium chloride residue was found to be .72 grams. What was the mass of the oxygen evolved in the experiment? If there is a balanced equation, if you could...

**chemistry**

Those are not the right answers

**chemistry**

A solution is 40% acetic acid by mass. The density of this solution is 1.049 g/mL. Calculate the mass of pure acetic acid in 170 mL of this solution at 20 C. Answer in units of g The density of a solution of sulfuric acid is 1.29 g/cm3 and it is 38.1% acid by mass. What volume...

**US History**

What is the Puritan concept of "calling" and how does it relate to the Puritan beliefs? Thanks for you help :)

**Physics**

A car travels in a straight line with an average velocity of 80 km/hr for 2.5 hours and then with an average velocity of 40 km/hr for 1.5 hours. a. Calculate the largest displacement for the 4-hour trip. b. Calculate the largest average velocity for the total trip in kilometer...

**Health**

d is wrong

**Chemistry**

A volume of 150mL of 0.35M HCl is to be prepared from 80% HCl stock solution. (Density of HCl = 1.191g/mL). Calculate the molarity of 80% HCl stock solution.

**Physics**

A 1.0 x 10^3 kg elevator carries a maximum load of 800.0 kg. A constant frictional force of 4.0 x 10^3 N retards the elevator's motion upward. What minimum power, in kilowatts, must the motor deliver to lift the fully loaded elevator at a constant speed of 3.0 m/s? Please ...

**reproduction**

why doesn't a women body reject the sperms since it is an external organism , instantly i.e, it should have produced the antibodies against it right?

**Physics**

thank you a lot

**Physics**

A small coin is inside a bowl. The bowl is a surface of revolution of the curve y=100x4 m−3. This coin slides around the inside of the bowl at a constant height of y=0.01 m above the bottom of the bowl. What is its angular velocity in rad/s? please just say the method , ...

**Physics**

how do we calculate speed ? time i know

**maths**

A ship is sailing due east at 18 knots runs into a 3 knot current moving 40 East of North. The resultant speed an direction of the ship are:

**math**

Explain, please?

**chemistry**

Thank you Dr. Bob

**chemistry**

Ok, so using Le Chatelier's Principle If you add heat to an exothermic reaction, the equilibrium will shift to the left. If you remove heat to an exothermic reaction, the equilibrium will shift to the right. What is it for an ENDOTHERMIC reaction? If you add a substance, t...

**Finance**

What does "loan amortization requirements" mean?

**Chemistry**

Yes, so in other terms, you are saying that exothermic reactions usually generate more, but endothermic reactions store more?

**Chemistry**

Ah ok, makes sense, thank you :) Also one more question if you don't mind, which produces more energy, exo or endo? Or does it depend on the delta H it gives you in the equation?

**Chemistry**

Ok, so in an when an endothermic reaction occurs, is it hot or cold? and why? Also what is it for an exothermic reaction? Thank you

**Chemistry**

Ok, so in an when an endothermic reaction occurs, is it hot or cold? and why? Also what is it for an exothermic reaction? Thank you

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