# Posts by K

Total # Posts: 928

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 ...

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.

i don't 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?

english
It's a lot easier than you think!!! You can look up the story and read the whole thing but if you don't feel like doing that there's many summaries and you'll for sure be able to do this one trust me!!(:

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

science
Blah, did you take the test all ready?

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 ...

biology
idk

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 :)

Ed-tech/History question~!

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 ...

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
47

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 ...

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 ...

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 ...

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 ...

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 ...

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...

physics
I believe the car brakes for 4.4 sec.

Biology
No im wrong i think its. A Am i right Mrs. Sue

Biology
I think its C am i right mrs. Sue

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 ...

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

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, ...

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

Eng
A is wrong because it should be its

Trigonometry
wrong man

MATHS

math
Why?

chemistry
Ok, so the shape of the metal affects the reaction rate, correct? And any shape, will increase the rate, right?

chemistry
If you add a metal piece to excess acid, what of listed factors below will increase, decrease, or have no impact on how fast a reaction happens? a) lower molarity (concentration) of a solution b) higher molarity (concentration)of a solution c) increase volume of a solution (...

Chemistry
Ok, so you just do .333/.333 =1 (NO) and .625/.333= 1.87 (O2) So, then you go back to your equation, and you see how 1 < 2(# of moles of NO in the equation), that means it is the limiting reactant Then you do the same thing with 1.87, and 1.87> 1( # of mole of O2), so ...

Chemistry
In order to find the limiting and/ or excess reactant, you have to first convert grams to moles, then once you have that you did the #s by the smallest mole #. Once you have that, you compare that to the coefficients of the balanced equation.

chemistry
Explain how dispersion forces, dipole-dipole forces, and hydrogen bonds (intermolecular forces) affect the 2 states of matter using phase changes and heating curves. What is the effect on vapor pressure with dispersion forces, dipole-dipole forces, and hydrogen bonds?

Chemistry

Chemistry
How many oxygen atoms are in a) 3.21 x 10^22 molecules CH3OH b) .250 mol C6H12O6 Is it a) 3.21 x 10^22 atoms b) 9.03 x 10^23 atoms

Chemistry
A bracelet containing .200 mol of metal atoms is 75% gold. How many particles of gold atoms are in the bracelet?

Chemistry
What are the Oxidation and Reducation reactions for these equations : BaCl2 + NaHCO3 -> BaCO3 + NaCl + HCl (carbon is the reduction reaction, but I don't know what the oxidation reaction is) CaCO3 + HCl -> CaCl2 + CO2 + H2O

chemistry
Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in the floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects (e....

math
What if it is something like 0 = 5?

math
Ok, so when you are solving an equation, and you have an answer such as 5x=0 , does that mean that it is no solution or all real #s? And, when the answer is 4=4 , does that mean it is no solution or all real #s? And when the answer is 2x=2x, does that mean it is no solution or...

chemistry
Use the formula (V1*P1) / T1 = (V2*P2)/ T2

Math
anyone can explain?

Math
Why the possible sets are 2^5?

Geometry

chemistry
Pipette 3 drops of oil into a test tube of water and shake. Describe what takes place and why? - Would it be the oil settles at the top of the water, because the oil is less dense, and its a non-polar substance, so it doesn't mix with a polar substance (water). Add 1 scoop...

chemistry
Ok, well it gives us the equation: CH4 + 2O2 --> CO2 + 2H20 ( I balanced it) And then it asks us to calculate: deltaHf (#of mol) I think we have to do that using the mole ratio and the balanced equation? Sorry if it's confusing :/

chemistry
How do you calculate deltaHf using the # of moles from a balanced equation? How do you connect the Law of Conservation of Energy to a Thermochemical Equation? Thanks so much!

government
What exactly is the war going on between the U.S. and Pakistan? Is it because the U.S. though Bin Laden was in Pakistan? Also is that war and the Afghanistan war still going on? From what I researched, they still are.

government
Is fiscal policy the same thing as a fiscal cliff? If not, then how do they differ? Also what are some important policies in foreign countries that affected citizens their citizens?

organic chemisty
acid based reaction takes place.

World History
Thank you :)

World History
Sorry, I meant the decade of 2000-2010

World History
What policies affected the citizens during the 21st century? For example: In the U.S. we had the Homeland Security Policy

All you have to do is add 16/24 and 15/24

Chemistry
Thanks for your help! Makes lots of sense :)

Chemistry
Ah, ok, so another question I have is how would you determine which elements are oxidized and reduced?

Chemistry
I'm having a little trouble determining oxidation numbers for elements in a redox reaction KMnO4+HCl--> MnCl2+Cl2+H2O+KCl So far what I have for the reactants side is: K= +1 Mn= +7 O4= -2 H= +1 Cl= -1 And for the products side I have: Mn= +2 Cl2= -1 Cl2(diatomic)= 0 H2...

physics
The figure below shows two current carrying wires and the directions of the currents they carry. The wires carry the following currents: I1 = 12.5 A and I2 = 9.8 A. Wire 1 is at (0, 4.0) mm; wire 2 is at (13.3, 0) mm; point P is at (13.3, 4.0) mm. webassign. net/userimages/...

chemistry
If 8.72 grams of oxalic acid, H2C2O4, a diprotic acid, is neutralized when 23.4 mL of a solution of KOH is added, what is the molarity of KOH? the topic is acid-base triation, and i have already converted the mass to moles,but I am having trouble finding the volume for the ...

chemistry
ha :) thanks so much, that helps lots, i don't know why i was over thinking it! you're awesome!

chemistry
how do i predict a conjugate a base? Ex: HBr. The conjugate base is Br- a. NH4+ b. H2O c. H2PO4

Chemistry
use the formula (V1*P1)/T1 = (V2*P2)/T2 and make sure all the units are converted correctly, so i believe you just convert 325ml to .325 L, and then convert -125oC to Kelvin, and once you plug in all yours #s solve, and then convert it back to oC since you will have your ...

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