Need Science Help?

[Death]

What volume of 0.500 mol/L calcium acetate contains 0.300 mol of acetate ions?

6.0 g of ammonium phosphate is dissolved in sufficient water to produce 300 mL of solution. What are the concentrations (in mol/L) of the ammonium ions and phosphate ions present?

 

[AltF4]

2) and 3) seem alright. You are right for 1) in a mathematical sense, but I was looking for a descriptive sense. You don't have to worry, its simplist definition is "mass/inertia in motion".

Thanks for the help.

Hey! I haven't answered anything in here yet. And since this was a physics question, I'll take a stab.

Momentum, conceptually, can be though of as "if the object hit you, how much would it push you?" Momentum is mass times velocity. That means that both the mass of the object, and the velocity matters. Just think about it for a moment...

A fly (the insect) can travel really fast. Up to 36 mph is what a quick google search told me. But when a fly runs into you, do you get knocked down? No. Why? Because it has very little mass. Momentum is a measure of both velocity AND mass, so a fly would need to be going WAY faster than 36 mph to knock you down.

Conversely, if a car going 36mph hit you, you would know about it! Why? Because a car has a lot of mass. Way more than the fly.

However, if you were to get hit by a glacier, very little would happen. A glacier is a giant mass of ice. But it moves startlingly slowly. It's velocity is so slow that it has very little momentum.

You might try to think of it like "What would hit a baseball further?". A fly would not hit a baseball very far. Neither would a glacier. But a car going 36 mph would! Does that help?

 

[SuperBowser]

For Death.

1) The first question is more of a maths question and you could solve it in a few different ways.

I think the easiest way to look at it is that you find 0.5 moles in 1 litre, by definition. Therefore, you would find 0.3 moles in 0.6 litres of solution. The numbers reduce by the same fraction.

2) Umm, your second question is a little more involved. I kinda sucked at chemistry in school but I'll give it a shot (sorry if it's wrong lol). The formula for ammonium phosphate is (NH4)3PO4. To work out concentration you need to know the number of moles present and the volume of solution (you are already given volume).

Number of moles = mass (g)/Molar mass

We know the mass is 6g. The Molar mass for ammonium phosphate is roughly 150. This makes 0.04 moles.

Now that we have the number of moles, you can work out the concentration! This is number of moles/volume (0.30 Litres).

Concentration of ammonium phosphate 0.133 mol/L. Now if we look at the original formula, you can see for 1 molecule of ammonium phosphate there is 1 phosphate ion and 3 ammonium ions.

Therefore, the concentration of phosphate ions is 0.13 mol/L.
The concentration of ammonium ions is 0.133 x 3 = 0.40 mol/L.

The numbers are kinda fugly, so I may be wrong. Hopefully someone else can say if that's right or if not where I went wrong

 

[GoldShadow]

What volume of 0.500 mol/L calcium acetate contains 0.300 mol of acetate ions?

SuperBowser's approach would be okay if this question were asking for moles of calcium ions, but it's asking for acetate ions. Acetate has a (-1) charge; calcium has a (+2) charge. Therefore, there are two moles of acetate ion per mol calcium acetate (or 1.00 mol/L acetate ion). So 0.300 L contains 0.300 mol of acetate ions in this case.

6.0 g of ammonium phosphate is dissolved in sufficient water to produce 300 mL of solution. What are the concentrations (in mol/L) of the ammonium ions and phosphate ions present?

SuperBowser is correct on this one.

 

[SuperBowser]

Whoops, I misread that question. Funny I get the easy one wrong

 

[metalmonstar]

Two large metal plates are parallel and close to each other. On their inner faces, the plates have excess surface charge densities of opposite signs and magnitude 7.00E-23 C/m^2. In unit vector notation what is the electric field at points to the left of the plats, to the right of them and between them?

 

[Death]

Agh! Some more physics problems I don't get!

It is estimated that one kilogram of body fat provide 3.8x10^7 J of energy. A 68 kg mountain climber decides to climb a mountain 4200 m high.

How much work does the climber do against gravity in climbing the mountain? (2.8 x 10^6 J).

If the body is 25% efficient at converting chemical potential energy stored as fat to mechanical energy, deter mine the amount of fat the climber will use doing the work to climb the mountain. (0.29 kg). ???

A 50 kg cyclist on a 100kg bike speeds up from 5.0 m/s to 10.0 m/s.

What was the total kinetic energy before acceleratin? (7.5 x 10^2 J)

Ek = 1/2mv^2 But this will not give the correct answer???


What was the total kinetic energy after accelerating? (3.) x 10^3 J)

How much work was done to increase the kinetic energy? (2.2 x 10^3 J)
Is it more work to speed up from 0 - 5.0 m/s or from 5.0 - 10.0 m/s?



A high jumper of mass 55 kg wishes to jump over a bar 1.8m above the ground. her centre of mass is located 1.00 m above ground.

If she wishes to clear the bar while travelling at a speed of 0.4 m/s how fast must she be travelling the instant her feet leave the ground? (4.0 m/s).

She lands on her back on a foam pad that is 0.4 m thick. At what speed wil she be travelling when she first makes contact with the pad? (5.3m/s).

Shortly after, she is at rest. What happened to the mechanical energy she had moments earlier?

 

[Lixivium]

Agh! Some more physics problems I don't get!

It is estimated that one kilogram of body fat provide 3.8x10^7 J of energy. A 68 kg mountain climber decides to climb a mountain 4200 m high.

How much work does the climber do against gravity in climbing the mountain? (2.8 x 10^6 J).

Work done against gravity = gravitational potential energy = mass * displacement * g

mass = 68 kg
displacement = 4200 m
g = 9.8 ~= 10 m/s^2

Do the math.

If the body is 25% efficient at converting chemical potential energy stored as fat to mechanical energy, deter mine the amount of fat the climber will use doing the work to climb the mountain. (0.29 kg). ???

If the body is 25% efficient, then actual energy produced from fat is:

1 kg fat = 0.25 * 3.8 x 10^7 J = 9.5 x 10^6 J (per kg of fat)

2.856 x 10^6 J * (1 kg fat / 9.5 x 10^6 J) = 0.29 kg fat

A 50 kg cyclist on a 100kg bike speeds up from 5.0 m/s to 10.0 m/s.

What was the total kinetic energy before acceleratin? (7.5 x 10^2 J)

Ek = 1/2mv^2 But this will not give the correct answer???


What was the total kinetic energy after accelerating? (3.) x 10^3 J)

How much work was done to increase the kinetic energy? (2.2 x 10^3 J)
Is it more work to speed up from 0 - 5.0 m/s or from 5.0 - 10.0 m/s?

I don't know about this one, the answers given seem wrong.

A high jumper of mass 55 kg wishes to jump over a bar 1.8m above the ground. her centre of mass is located 1.00 m above ground.

If she wishes to clear the bar while travelling at a speed of 0.4 m/s how fast must she be travelling the instant her feet leave the ground? (4.0 m/s).

She lands on her back on a foam pad that is 0.4 m thick. At what speed wil she be travelling when she first makes contact with the pad? (5.3m/s).

Shortly after, she is at rest. What happened to the mechanical energy she had moments earlier?

Let's assume that to clear the bar she just has to raise her center of mass above it (from 1.00 m to 1.8 m).

At a height of 1.8 m, (the change in) her gravitational potential energy will equal the kinetic energy she puts into jumping:

m * g * (delta)h = 1/2 * m * v^2
g * h = 1/2 * v^2
v = sqrt(2 * g * h)

Do the math.

 

[Death]

Oh, thanks a lot. Whoops! A 100 kg bike seems a little too heavy, no? It should be 10 kg which means it now works out. Thanks anyway though

 

[Proud_Smash_N00b]

"Will a grandfather clock that is accurate at 20 degrees C run fast or slow when the temperature is 30 degrees C? The clock uses a pendulum that is supported on a long thin brass rod."

Does it run faster because the brass expands as the temperature rises?

Thanks

 

[Knyaguy]

"Will a grandfather clock that is accurate at 20 degrees C run fast or slow when the temperature is 30 degrees C? The clock uses a pendulum that is supported on a long thin brass rod."

Does it run faster because the brass expands as the temperature rises?

Thanks

I'm not in physics but here goes; If the brass expands than the mass would still be the same, so it wouldn't move any faster. It would just take up more space. I'm probably wrong but thats what I think.

 

[Lixivium]

The frequency of a pendulum depends on its length but not its mass.

The thin brass rod would lengthen (a tiny bit), but the mass remains the same, so the clock would slow down.

 

[Niiro]

um, anyone know how to use scientific evidence to evaluate Darwin's theory of evolution by natural selection?

 

[GoldShadow]

um, anyone know how to use scientific evidence to evaluate Darwin's theory of evolution by natural selection?

Not entirely sure what you're asking, but check out my posts from this:
http://www.smashboards.com/showthread.php?p=6024694#post6024694

 

[Niiro]

i actually used that in my paper/homework/test thingy, and i just got a ****in 98. pwnage.

 

[Proud_Smash_N00b]

Another question:
What do you guys think are good extra credit projects regarding heat, gases (ideal gas laws etc.), and thermodynamics? I can't think of any off the top of my head and I might need a little help. Thanks =]

 

[Death]

I Need some chemistry help QUICK!! I have a test tomorrow but I was sick when we covered all these question and I don't know how to do them/I can't get the correct answer.

An aqueous solution of a certain salt contains chloride ions. A sample of this solution was made by dissolving 17.59 g of the salt in a 1 L volumetric flask. Then 25.00 mL of the solution was treated with excess silver nitrate. The precipitate, AgCl was filtered and dried. IF the mass of the dry precipitate was 47.35 g, what was the mass percent of chloride ions in the solution?

The active ingredient in some rat poisions in thallium sulfate, Tl2SO4. A chemist takes a 500 mg sample of this and adds potassium iodide to precipitate thallium iodide. When the precipitate is dried its mass is 200 mg. What is the mass percent of Tl2SO4 in the poison?

To generate hydrogen gas, a student adds 5.77 g of mossy zinc to 80.1 mL of 4.00 mol/L HCL in a flask. When the reaction is over, what is the concentration of aqueous zinc chloride in the flask?

PLEASE HELP!!

 

[SuperBowser]

Well they're all plays on the formula no. of moles = mass/Molar mass and ratios.

Sometimes it helps to focus on what the question wants and work backwards from there. The first question is basically asking you to find the mass of chloride ions in the solution.

To do this, you need to first find the mass of chlorine in the compound of AgCl (remember the silver nitrate was added in excess, therefore all the chloride ions had to be used up from the solution). The molar mass of AgCl (adding them up from a periodic table) is roughly 143. The molar mass of chlorine is 35.5. From this you can infer that a sample of 47.35 grams contains 11.75 grams.

11.73/25 (the original solution's mass) = roughly 47%.

Hopefully that's the right answer . You should try applying the same principles to the other questions.

edit: i was wondering, does anyone around here know a good site for learning human anatomy? I hate using textbooks and wikipedia is pretty terrible for this...

 

[Death]

Ok thanks. And about the human anatomy, really, even if you detest studying from books, try to find "Principles of Anatomy and Physiology" ~ Tortora and Grabowski. It is possibly the BEST book I have ever read in terms of the human body. Check it out, seriously.

 

[AltF4]

Another question:
What do you guys think are good extra credit projects regarding heat, gases (ideal gas laws etc.), and thermodynamics? I can't think of any off the top of my head and I might need a little help. Thanks =]

Maybe something playing with supercooled or superheated water? Both are freakin' awesome.

 

[Proud_Smash_N00b]

Maybe something playing with supercooled or superheated water? Both are freakin' awesome.

Man those are good ideas but idk how to do the supercooled experiment and the superheated one may be dangerous lol

and now for some help on electrons: (if anyone can answer it that will be awesome)
How many electrons does it take to make a -30 x 10^-6 C?
do just multiply (or divide) it by 1.6 x 10^-19 C?
Thanks =]

 

[AltF4]

Supercooling water is really easy, relatively. You just have to get the settings right. The Wikipedia page is fairly informative, as is just "googling around".

Essentially, you have to get really pure water, then bring it below freezing temperature very slowly. Taking tap water (even bottled water... which very often IS just tap water!) won't work. There are particulates which the ice will freeze to. And sticking it in the freezer won't work, it needs to chill much slower. (Though the second restriction, in practice, might be less strict)

 

[cman]

Does anyone know why charges gather at sharp points? My text books declares that it must "assert without proof" for now, and none of the physics teachers in my school know exactly why. I'm in a high school AP class btw, not college.

 

[Death]

I have a question on lung capacity and volume:

Why might a doctor deliberately deflate a patient's lung?

He may do so to collapse the lung which would allow it to rest and heal rapidly after surgery or during treatment of tuberculosis. The lung can be re-inflated by the doctor breaking the seal and filling the lung with oxygen.

My teacher said that we had to find ANOTHER reason but I can't think of anything else??

 

[SuperBowser]

That's a pretty difficult question. The only indications I can think of from the top of my head are during cardiothoracic surgery...

Surgeons might use one lung ventilation (ie. deflating the other side) for a fair few reasons. It can be to: prevent contamination of one lung to the other in a haemorrhage or infection, washing out of a single section of a lung (bronchopulmonary lavage) and in upper lobectomies/pneumonectomies.

btw, i already have an anatomy textbook and i want no more! it's just sooooo slow to take out a massive textbook and find a page to learn 5 facts .

 

[¯\_S.(ツ).L.I.D._/¯]

If someone swallowed a small sealed container with dry ice in it and it exploded inside them, would they die?

(I'm not trying to troll I actually always wondered this since I learned about Dry Ice in 5th grade.)

 

[Death]

Does anyone know where I can purchase a bell jar? I need one to demonstrate how the respiratory system works. This is for a 2% increase in my final mark so I kinda need to know!

 

[Deleted member]

How many ATPs are made in that Electron Transport thing? Trying to help my nephew and I forget all this stuff.

 

[.CMW.]

Well I was gone for the last few weeks from my Chemistry class and we are having a test TOMORROW! AHHH!!! I was in the hospital with a broken arm (typing with one hand woot woot) and I understood none of the material I had with me, and now we have a test. I really need your help, our teacher gave us an assignment to study for the test and I was wondering if some of you smarties could help me. I really need these problems explained to me, I may be able to pass at least if I see these problems done with explanation. Sorry to ask so much.

For each of the following unbalanced equations, calculate how many milligrams of each product would be produced by complete reactions of 10.0 mg of the reactant indicated in italics. Indicate clearly the mole ratio used for the conversion.
a. FeSO4 (aq) + K2CO3 -> FeCO3(s) + K2SO4(aq)
b. Cr(s) + SnCl4(l) -> CrCl3(s) + Sn(s)
c. Fe(s) + S8(s) -> Fe2S3(s)
d. Ag(s) + HNO3(aq) + H20(l) + NO(g)


Small quantities of oxygen gas can be generated in the lab by the decomposition of hydrogen peroxide. The unbalanced equation for the reaction is
H202(aq) -> H20 + 02(g)
Calculate the mass of oxygen produced when 10.00g of hydrogen peroxide decomposes.

Ammonium nitrate has been used as a high explosive because it is unstable and decomposes into several gaseous substances. The rapid expansion of the gaseous substances produces the explosive force.
NH4NO3(s) -> N2(g) + 02(g) +H20(g)
Calculate the mass of each product gas if 1.25 g of ammonium nitrate reacts.

Elemental fluorine and chlorine gases are very reactive. For example, they react with each other to form chlorine monofluoride.
Cl2(g) + F2(g) -> 2ClF(g)
Calculate the mass of chlorine gas required to produce 5.00 + 10^-3g of chlorine monofluoride given an excess of fluorine gas.

Both propane (C3H8) and butane (C4H10) react with oxygen gas to form carbon dioxide and water. If you have equal masses of each, which will require a greater mass of oxygen to react?


I really appreciate the help, I would prefer passing this class. lol. All the numbers are below the element, you can't raise or lower numbers when typing. The one -3 preceded by a ^ is raised above the element.

Thank you so much, .CMW.
__________________

 

[Seagull Joe]

hehe im a chem major.if i have time ill solve these problems tommorrow afternoon.

 

[GoldShadow]

Hope you've still got time to look this over before your test. I don't have the time or will to answer each question, so I'll just show you how they're done and provide an example.

For each of the following unbalanced equations, calculate how many milligrams of each product would be produced by complete reactions of 10.0 mg of the reactant indicated in italics. Indicate clearly the mole ratio used for the conversion.
a. FeSO4 (aq) + K2CO3 -> FeCO3(s) + K2SO4(aq)
b. Cr(s) + SnCl4(l) -> CrCl3(s) + Sn(s)
c. Fe(s) + S8(s) -> Fe2S3(s)
d. Ag(s) + HNO3(aq) + H20(l) + NO(g)

To solve these problems, first you need to balance the equation so that the moles of each element on the left equal the number of moles of that element on the right. So let's look at c as an example. The balanced equation would be:

16Fe(s) + 3S8(s) -> 8Fe2S3(s)

Next, you use the information you're given to calculate whatever the question asks for. The question says that you have to find the amount of product formed if given 10 mg of the reactant in italics; since you didn't italicize anything, I'll just pick Fe for this example. Say you're given 10 mg (.01 g) of Fe for this reaction. First calculate how many moles that is. The molar mass of Fe is 56g. So you have (0.01g Fe)/(56 g/mol Fe)=0.00018 mols Fe. Assuming that the sulfur (S8) is present in excess, the Fe will react completely to produce the product.
This is where the molar ratios come in. For every 16 mols of Fe in the reactants, you have 8 moles of Fe2S3 produced, so if we have 0.00018 mol Fe, then we will get (0.00018 mol Fe)*[(8 mol Fe2S3)/(16 mol Fe)], which can be written more simply as (0.00018)*(1/2), or 0.00009 mol Fe2S3.
Now that we know the number of mols of product, we need to figure out the mass of the product. To do this, simply multiply the number of moles (in this case, 0.00009) by the molar mass (for Fe2S3, it's 208): 0.00009 mol Fe2S3*208 g/mol Fe2S3 = 0.01872 g Fe2S3, or 18.72 mg Fe2S3.

If you have multiple products, use the exact same process; you just need to figure out how many moles of each product are produced (based on the moles of reactant you're given) and then multiply by that product's molar mass.

Small quantities of oxygen gas can be generated in the lab by the decomposition of hydrogen peroxide. The unbalanced equation for the reaction is
H202(aq) -> H20 + 02(g)
Calculate the mass of oxygen produced when 10.00g of hydrogen peroxide decomposes.

Use the exact same method as above.

Ammonium nitrate has been used as a high explosive because it is unstable and decomposes into several gaseous substances. The rapid expansion of the gaseous substances produces the explosive force.
NH4NO3(s) -> N2(g) + 02(g) +H20(g)
Calculate the mass of each product gas if 1.25 g of ammonium nitrate reacts.

Same process as above.

Elemental fluorine and chlorine gases are very reactive. For example, they react with each other to form chlorine monofluoride.
Cl2(g) + F2(g) -> 2ClF(g)
Calculate the mass of chlorine gas required to produce 5.00 + 10^-3g of chlorine monofluoride given an excess of fluorine gas.

Same process, but this time in the opposite direction. You're given the amount of product. Figure out how many moles that is; then figure out how many moles of Cl2 is needed to make that (hint: for each mole of Cl2, two moles of ClF are produced. You need to use this fact to multiply by the right molar ratio). Once you've determined the moles of Cl2, just figure out the mass of Cl2 by multiplying by the molar mass of Cl2.

Both propane (C3H8) and butane (C4H10) react with oxygen gas to form carbon dioxide and water. If you have equal masses of each, which will require a greater mass of oxygen to react?

These are examples of a combustion reaction, so you can easily figure out the balanced equation for each.
For any alkane/hydrocarbon combustion reaction, you have the following equation (where x and y are the subscripts for carbon and hydrogen):
CxHy + ?O2 --> ?CO2 + ?H2O

For propane:
C3H8 + ?O2 --> ?CO2 + ?H2O

First use the fact that all the carbon is converted to CO2, so for each mole of carbon on the left, you'll have the same number of moles of CO2 on the right:

C3H8 + ?O2 --> 3CO2 + ?H2O

Then realize that all the hydrogen on the left goes into making H2O on the right, so all the moles of H on the left find their way into the H2O on the right, which allows us to determine this:

C3H8 + ?O2 --> 3CO2 + 4H2O

Now that we know the number of O on the right, we can fill in the last missing coefficient:

C3H8 + 5O2 --> 3CO2 + 4H2O

Using the same method for butane:
C4H10 + 6.5O2 --> 4CO2 + 5H2O

Now that you have balanced equations for each, you can come up with an answer. Question says that given the same mass of reactant hydrocarbon, which will use up more O2? Arbitrarily pick a mass; say, 100 g. Figure out how many moles of propane are in 100 g and how much O2 will be used (hint: for each mol of C3H8, you will use 5 moles of O2). Then do the same for butane (for each mol of C4H10, you will use 6.5 mols of O2). And there's your answer.

 

[GoldShadow]

Alright, I know these were posted several weeks ago but better late than never, right?

How many ATPs are made in that Electron Transport thing? Trying to help my nephew and I forget all this stuff.

In aerobic cell respiration, about 34-36 ATP are produced per molecule of glucose. 2 from glycolysis, 2 from the TCA cycle, and 30-32 from the electron transport chain. http://en.wikipedia.org/wiki/Cellular_respiration for more info.

If someone swallowed a small sealed container with dry ice in it and it exploded inside them, would they die?

(I'm not trying to troll I actually always wondered this since I learned about Dry Ice in 5th grade.)

Like a dry ice bomb? Yeah, those can be pretty powerful, I imagine it would do one hell of a number on your insides!

 

[Death]

I have a physics question and I'm hoping someone will know something about it...

Draw a sketch to explain how a magnetic circuit-breaker might operate to limit the current flowing through a conductor to 15 A.


????? We did not even learn this stuff.

 

[Death]

I really need help for my DC motor that I built. It is due in 3 days so I would appreciate if someone could answer before then.

So I basically built a motor that resembles the one found here: http://sci-toys.com/scitoys/scitoys/electro/electro3.html#two_coil

The thing is, for a higher mark, I need to get the motor to self-start which is a bit difficult with this motor (I usually have to give the rotor a nudge to get it going). I asked my teacher and he said I should try using paperclips He is purposely not helping people directly and only giving hints.

I know that I need some kind of counter-weight to drag the rotor from the starting position to go through a half-swing.


How can I get it start by itself?

 

[Death]

What natural activity of a leaf might cause the stomata to open?

 

[GoldShadow]

Transpiration, and gas exchange resulting from photosynthesis (CO2 in, O2 out).

 

[Death]

he question is to from ethyl 3-hydroxybutanoate from an alcohol and alkene of my own choice. Now the question is, how can I form 3-hydroxybutanal (which is what I will need to form 3-hydroxybutanoic acid) from an alcohol?

Wouldn't this warrant the controlled oxidation of a secondary alcohol, which CAN'T form aldehydes?? HELP

 

[.Marik]

Subscribed.

I'll be sure to pop in here once in a while.

Nomenclature is pretty fun.

 

[Death]

Hmm so I managed to figure out the problem: 3-hydroxybutanal can be formed from controlled oxidation of 1,3-butanediol. Is this correct/can polyalcohols form aldehydes?

 

[Dark_Bomb]

This topic is so beautiful. Science is truely amazing, especialy biology.
Would it be okay if I jumped in and helped people out here too? I'd love to be able to.