Posts by Dr Russ

Total # Posts: 1,609

I need correct answers for all please !
This is a site for home work help. We do not do the work for you.

Chemistry
This looks very much like the S104 TMA04 question?

Chemistry
we will assume that the aqueous solutions fill the 1 L flask. At start 1 mol A + 2 mol B and 0 mol C At equilibrium 1-2x mol of A and 2-x mol of B and 3x mol of C so x=0.2 M K=x^3/(1-2x)^2(2-x) K=(0.2)^3/(0.6)^2(1.8) K=0.008/(0.36)(1.8) K=0.012 (with no units)

Chemistry
2C:6H or 1C:3H

Chemistry-help needed
I tend to put the mixture in the developing chamber a while before I run the TLCs. Not too important if all you are doing is looking for the disappearance of starting materials/appearance of product. Getting the chamber saturated can be important with prep-TLCs where you want ...

chemistry
So lets say we have 100 mL of air then this will contain 20.9 mL oxygen. Thus 100 mL/20.9 of air will contain 1 mL of oxygen. So how many mL of air contain 150 mL of oxygen?

AP CHEMISTRY NEED HELP PLEASE!
You need to set these up so that if you add up the equations you get the equation in the question. So we need to get to C3H6 (g) + 9/2 O2 (g) -> 3CO2 + 3H2O C(s)+O2 (g) -> CO2 (g) dH= -394kJ and we need three of these so A. 3C(s)+3O2 (g) -> 3CO2 (g) dH= -1182kJ H2 (g...

chemistry
If we take the specific heat of water as 4.18 j/g/K Do this by heat balance Heat before water 250x(25+273)x4.18 metal 41.6x(100+273)xk after water 250x(26.4+273)x4.18 metal 41.6x(26.4+273)xk so 311410J + 15516.8k J = 312873J + 12455k J solve for k I got 0.4778 J/g/k so B

Chemistry
Yes, from general knowledge A is exothermic B is exothermic C is endothermic (the reverse reaction is exothermic!) D is the formation of F2(g) from its elements in their standard states. All elements in their standard states have a standard enthalpy of formation of zero, as ...

Chemistry
1. You will have results for this. 2. You need the correct formula which is Na2CO3. To decide if there is a linear relation ship plot the number of moles of CO2 produced (y-axis) against moles of Na2CO3 used (x-axis) To calculate the number of moles this is mass/molar mass. ...

science
Again this has come up before http://www.jiskha.com/display.cgi?id=1191713796

scientist
This one has coem up before http://www.jiskha.com/display.cgi?id=1270701200

10th Grade Chem
See if you can find one of the periodic table on the internet that shows pictures of the elements. If you do you will see that the vast majority of the elements are shiny metal solids. Those that are not shiny metal solids are the exceptions. There are only two elements (...

Chemsitry
Better of you gave an answer for us to comment on. Lets sat we have the decay of uranium (mass=235, atomic number=92) to thorium (mass=231, atomic number=90) plus He nucleus(mass=4, atomic number=2) Note that the mass number (235=231+4) and atomic number balances (92=90+2) So ...

science
Making the ice surface rough so that it scatters the incoming light is most effective to slow down melting. Alternatively if you can change the colour of the surface under the ice this will affect the rate of melting. Ice on a black road melts faster than that on a white surface.

scientific notation
Unless you have been told otherwise I would recommend that you include the units in a conversion such as this. While it might seem pedantic here, it can help a great deal when the units are less familiar. 365 d y^-1 x 24 h d^-1 x 60 min h^-1 x 60 s min^-1 = ___ s y^-1

Chemistry
I'll get you started.... 8.00 mass percent means that 100 g of the solution as 8.00 g of ammonia and 94.00 g of water. The 100 g of solution will have a volume of 100 g / 0.9651 g/ml =103.61 ml Thus (based on NH3) the 8.00 g represents 8.00 g /17 g mol =0.4706 mol so ...

chemistry
use PV=nRT where n is the total number of moles. Use V=25.00 L P =1.00 atm you needed to calculate n for the first part. Make sure that use the correct value for R based on the units.

Science
Your question doesn't make sense

science
The key here is 'what do YOU think....'

chemistry
Please try to get into the habit of using the correct symbols as this aids your communication on the topic. (I will assume here that the reaction is going to completion) Start from a balanced equation 3H2 + N2 -> 2NH3 then calculate the number of moles of each of the ...

Math
3x^7 = 81x^4 divided both sides by 3 x^7 = 27x^4 divided both sides by x^4 x^3 = 27 take the cube root of each side x=3

Chemistry
You weigh out 196.07mg ferrous ammounium sulfate (FW 392.14) to prepare 250mL of solution which is 0.002M with respect to that compound. The salt is quantitatively transferred into a 250mL volumetric flask and 8mL of 3M H2SO4 is added and then diluted to the mark (call this ...

Math
So we need to factorise x^3+2x^2-x-2=0 If we start off by guessing that one of the solutions is x=-1, i.e. one of the factors is (x+1) then by division (x^3+2x^2-x-2)/(x+1) = (x^2+x-2) for which the factors are (x-1)(x+2) so the solutions are x=-1, x=+1, x=-2

chemistry! URGENT
We need the molarity so we will need to be working in moles and therefore need the molar mass of the steroid. I make this C. 12 x 20 = 240 H. 29 x 1 = 29 F. 19 x 1 = 19 O. 3 x 16 = 48 total = 336 i.e. 336 g mol^-1 If 10.0 mg is dissolved taken then this is 0.0100 g /336 g mol...

Site not working correctly/Physics
Try high lighting the whole text and copying and pasting to say a Word page.

Science
There are no electrons in the first free level of any element. But I suspect it is a typo and it means the first three levels? Silicon has electronic configuation of 1s2 2s2 2p6 3s2 3p2 So I suspect the answer that is being looked for is 10.

URGENT chemistry
As we are not given Kw in the question, my answer would have d)

chemistry
Thank you DrBob, I missed that. Dr Russ

chemistry
Use P=nRT/V n=27 g /18 g mole^-1 V and T are in the question. You need to find the correct value for R

chemistry
if you react 37.0ml of .762M sulfuric acid..... with what??

Chemistry
Not solveable You need to know: what the reaction was quantities of materials used units of 5.70 (g, kg, lb, oz, mole?)

Organic Chem
There are a couple of possible reasons. I don't know what red leaf extract is?? Is it red tea extract? I take it that the stationary phase of the TLC is silica gel? It is quite likely that the extact contains a number of nitrogen containing compounds, such as alkaloids (it...

chemistry
Be sure your answer has the correct number of significant digits.. As both the starting values are to 2 sig figs, and assuming that you use molar masses that have 3 sig figs or greater then the answer should be to 3 sig figs.

science-biology
Answered below

science-biology
My understanding is that is not possible. The only blood groups from an O mother are O, A or B, depending on the blood group of the father, but not AB. The mother would have to be A, B or AB. So I would conclude that the mother is not the child's natural mother. Unless I ...

chemistry
If a solution is 1.54% w/w then for 100 g of solution 1.54 g of the soluton is NaCl and the other 98.46 g is water. If we have 2 x 1.54 g of NaCl we must have 2 x 98.46 g of water. So if we have 6.96 g of NaCl how much water?

science
Assume 4 tyres and mass evenly distributed. Then use pressure= force/area 1 Pa = 1 N m^-2 force = mass x acceleration I would assume that g= 9.8 m s^-2

science
I take we are taking about the visible spectra (Balmer Series)? The two spectra have similar number of lines as below, although some are very feint. That a line apears in the visible spectrum will depend on the separation of the energy levels. We do not see transitions to ...

science
For the first one Use Ke = 0.5 mv^2 Ke = 200 MJ or 2 x 10^8 J m= 100,000 tonnes or 1 x 10^8 kg substitue and solve for v. the same approach will answer the second one. Note that speed is in km per hour not Km per hour.

Earth Science
You have essentially two possibilities, life started on Earth abiogenesis ((Broken Link Removed) or it arrived here from elsewhere (Panspermia see (Broken Link Removed) If you google abiogenesis or panspermia you will get more information. The above two wiki pages will get you...

Chemistry
You need to choose an atom. Helium is the easiest which has protons, neutrons and electrons. I presume you are looking for a Bohr/Rutherford Model ((Broken Link Removed) Thus for helium you will need a nucleus of 2 protons and 2 neutrons around which there is a circle ...

SCIENCE
Please do not write in capitals, it is considered to be the equivalent of shouting. Roots cannot be decomposers as they are not an organism. A decomposer is an ORGANISM whose ecological function involves the recycling of nutrients by performing the natural process of ...

chemistry
You are calculating w/w%, which is mass (A) x100%/(total mass A + M) From the density we can find the mass of ethanol M=0.789 g/ml x 175 ml A=42.9 g

Organic Chemistry
This sounds like an elimination reaction problem, in which case the answer is usually a discussion of E1 v E2 so see http://en.wikipedia.org/wiki/Elimination_reaction

chemistry
How about suugesting an answer?

chemistry
You need to know the Kw for water at the temperature of the fruit. There is a table of Kw versus temperature here http://www.chemguide.co.uk/physical/acidbaseeqia/kw.html then use [H+][OH-]=Kw to find [H+] the find pH Alternatively find pOH find pKw then pH=pKw-pOH

chemistry
Nitrous acid is HNO2

chemistry
from the equation HCl + KOH -> KCl + H2O 1 mole of HCl reacts with 1 mole of KOH Then if we use M1V1=M2V2 42.5 ml x 0.110 M = 25.0 ml x X X=42.5 ml x 0.110 ml/25.0 ml [Incidently you can use 'school boy logic' here to eliminate amswers. If we only have 25.0 ml and ...

basic question
There are a number of tutors who volunteer to answer questions and who are in various time zones/countries. Consquently there may not be always be a specialist available for some questions. The easiest way for us to spot an unanswered question is a single posting, if there is ...

chemistry
You need to know the Kw for water at the temperature of the wine. There is a table of Kw versus temperature here http://www.chemguide.co.uk/physical/acidbaseeqia/kw.html then use [H+][OH-]=Kw to find [OH-]

World Geography
Nigeria? Again you need to decide which classification of biomes you are using. Is this list in your text book/notes? Take a look at a map of Nigeria and you will see that there are a number of biomes represented. Below are the WWF 14 biomes, which of these are represented in ...

World Geography
If we take the definition of biome as "A major regional or global biotic community, such as a grassland or desert, characterized chiefly by the dominant forms of plant life and the prevailing climate" The highest population density would depend on whether the ...

chemistry
Products of alkynes with what? Alkynes will undergo addition reactions so will give similar products to alkenes where the reagent has added twice across the triple bond. Alkynes will under go Diels Alder reactions with a diene to give a cyclohexadiene. Alkynes also under go ...

Math
This crosses the y axis when x=0 so y=16 This crosses the x axis when y=0 0=9x^2+24x+16 0=(x+4/3)^2 so x=-4/3

Mathematics
By symbols A-B=9 AxB=162 so A=9+B (9+B)B=162 9B+B^2=162 B^2+9B-162=0 so B=-18 or 9 correspondingly from AxB=162 A=-9 or 18 check against A-B=9 -9--18=9 18-9=9

chemistry
The question is asking for pressure so 29.0 L cannot be correct. P1/T1 =P2/T2 where P is the pressure and T is the temperature in kelvin. 35.0C is (273.15+35.0) K =308.15 K 76.0C is (273.15+76.0) K =349.15 K P1=1.00 atm so 1.00 atm / 308.15 K = P2 / 349.15 K P2 = 1.133 atm ...

strategic manaement
Can't really help with this one as you know what business you are looking at and hence the rival businesses. I would be tempted to introduce the rival businesses over a couple of slides, but very generally. Then use a separate PowerPoint slide for each of the ...

fp/101
You should discuss risk in terms of probability and consequence. One good way to present the results is to do a chart or grid with probability (low, med, high) on one axis and consequence (none, medium, severe) on the other. This gives a 3x3 grid, but you could do say 5x5. The...

Algebra
Revenue – Cost = Profit substitute the terms [4x(x+6)] - [5x(x-4)] = 160,000 expand 4x^2 + 24x - 5x^2 + 20x = 160,000 combine like terms -x^2 + 44x - 160,000 = 0

Chemistry
OK so you need to convert the mass of 225 lb to mg. if we take 1 lb =454 g, or the conversion factor is 454 g lb^-1 then 225 lb is 225 lb x 454 g lb^-1 which in mg is M = 225 lb x 454 g lb^-1 x 1000 mg g^-1 volume = mass/density volume = M/(25.0 mg/mL)

Chemistry
You can't without knowing the mass. or do you mean How do you convert 25.0 mg/mL to mg/cc?

Chemistry
This question has been answered before. "the value of Kw is 2.92 10-14" ?? units are missing Given that [H+][OH-]=Kw and that [H+] = [OH-] for pure water then [H+][OH-]=[H+][H+]=2.92 x 10^-14 [H+]^2= 2.92 x 10^-14 [H+] = sqrt(2.92 x 10^-14) but this is missing the ...

Maths
If the field has sides of length L then the total distance around the field is 4L. If our field uses 4L of fencing at a cost of 10 per metre then 4L x 10 = 400 solve for L

Math (linear algebra)
x- 2y+ 3z = 5 3x + y = -5 -2x+y + z = 8 First thing to check is that we have three equations and three unknowns, which is fine. If there are more unknowns than equations then there is a problem with the question. x- 2y+ 3z = 5 3x + y = -5 -2x+y + z = 8 we need to eliminate one...

SCIENCE
The wikipedia page is good http://en.wikipedia.org/wiki/Sonar

Chemistry
Not hard to find see http://en.wikipedia.org/wiki/Isotopes_of_molybdenum or the table of isotopes in 'Handbook of chemistry and physics' Mo-86 is a positron emitter with a half life of 19.6 s

earth
Acceleration due to gravity on the moon is 1.63 m s^-2 If acceleration due to gravity on the Earth is 9.8 m s^-2 then the weight of the man on the moon is 720 N x 1.63 m s^-2/9.8 m s^-2

CHEMISTRY
ch3-ch2-ch2-ch(c triple bond CH)-CH2-CH2-CH2-CH3 Doesn't make sense, do you mean CH3-CH2-CH2-C(triple bond)C-CH2-CH2-CH2-CH3 9 carbon chain so a nonane derivative. The triple bond starts at C4 so non-4-yne (or 4-nonyne)

physics
"A load of mass 80kg fell dwn from d floor of a lorry whch is 1.2m high.calculate wrk dne by gravity on d land " If you can write the question in normal plain english you are more likely to get a correct answer. You should also get in the habit of correctly spacing ...

JavaScript
You are probably best to post the method so far. However, switch statements are shorthands for a group of if statements that all relate to the same quantity as: if (x == 0) doSomething0(); else if (x == 1) doSomething1(); else if (x == 2) doSomething2(); else if (x == 3) ...

Solubility of gases
I used to use the handbook of chemistry and physics "Rubber book" for this sort of problem, I presume there must be one available on-line or you could check you college library. So for the gases above CO2 is partially soluble in water but can be collected by downward...

Chem
Seawater contains approximately 3.5% by mass and has a density of 1.02 g/mL. What volume of seawater contains 5.5g of sodium. What a badly worded question! There is no way you can calulate the mass of sodium from the information given as you need to know what proportion of the...

Geometry-Please Help
If the garden is square and has sides of n metres, then each side will require 2+(n-1) posts with the 2 posts at the corners. As the corner posts are common with adjacent sides then the total number of posts is 4 sides of n-1 plus 4 corner posts. 4(n-1) + 4. if n=10 then the ...

venn
Draw one large circle (B) and with in this draw two smaller circles (A and C) so that A and C are within B and do not intersect.

chem
Calculate molar mass of C2H6 = 30 g mole Number of moles is then 275 g/30 g mol^-1 = 9.2 mole 1 mole contains 6.02 x 10^23 molecules (Avogadro's number) So number of molecules = 6.02 x 10^23 molecules mole^-1 x 9.2 mole =

Science
The focus of an earthquake is the point below the Earth's surface from which the earthquake (seismic waves) appear to originate. The epicentre is the point on the Earth's surface directly above the focus.

chemistry
This is not a site where we do the home work for you. Have a go at the questions and we will comment/correct as needed.

chemistry
This is a repeat

chemistry
Calculate the number of moles of Zn from M=10g/molar mass of Zn calculate molar mass of ZnCl2 mass produced is then M x molar mass of ZnCl2

chemistry
Relative atomic mass = 20.8 g Let the fraction that is element 20 = x thus the fraction that is element 21=1-x so 20x +21(1-x) = 20.8 20x + 21 -21x=20.8 -1x=-0.2 x=0.2 and 1-x=0.8 so 20% element 20 and 80% element 21.

algebra
a) L = 60/(3+17e^-0.1t) Substitute t=0, remember that any number to the power 0=1 b) L = 60/(3+17e^-0.1t) substitute L=10 10=60/(3+17e^-0.1t) 3+17e^-0.1t=6 17e^-0.1t = 3 e^-0.1t=3/17 ln(e^-0.1t)=ln(3/17) -0.1t=ln(3/17)=-1.7346 0.1t=1.7346 t=17.346 hours But check the maths!

science
Give examples of how humans have increased their food supply and what effects these methods have on the environment overall. This is really one where you need to give ideas and we will comment if you like. I am sure this question has been answered before on here. Anyway you ...

Chemistry
I assume we are talking about pure (=glacial) acetic acid? In this case you need to know the density, which is 1.05 g cm^-3, and the molar mass which is 60 g mole^-1 Thus the 50 ml has a mass of 1.05 g cm^-3 x 50 cm^3 = 52.5 g hence the number of moles is 52.5 g/60 g mole^-1...

science chemistry
The general formula for alkanes is CnH(2n+2) n=1 methane (CH4) n=2 ethane (C2H6) and so on to C100H202 or hectane I don't understand what is meant by "enumerate the 100 alkanes"

Org Chem. I
They are drawn on the wikipedia page http://en.wikipedia.org/wiki/Carvone I would be tempted to redraw them using a Fisher projection http://en.wikipedia.org/wiki/Fischer_projection to demonstrate you understand the application of the C-I-P rules.

math
h(x)=2x-5 h(0)= here we substitute 0 for x h(0)= 2.0+5=5 h(-8)= here we substitute -8 for x I'll let you do this one.

Chemistry
Not a great deal of chemistry here as it is by proportion. He melted 30 grams of Au (gold) with 30 grams of Pb. This melting process resulted to 42 grams of an Au-Pb alloy and some leftover Pb. So assume all the gold is incorporated then (42-30) g of lead used, which is 12 g. ...

chemistry
Molarity = number of moles/total vol (L) number of moles = 2.24 g/40.0 g mole^-1 volume = 0.5000 L hence calculate molarity (take care with sig figs)

chemistry
As from the equation the ratio is 1:1 Use M1V1=M2V2 (i.e. working in mmoles) thus 43.50 ml x 0.105 M (NaOH) = 5.00 ml x X where X is the molarity of the vinegar and taek care with the sig figs.

Science
A salinity meter placed in a tidal pool shows a dramatic decrease in salinity between 2 A.M. and 3 A.M it rained? This decrease is followed by a gradual rise in salinity from 11 A.M. until 4 P.M. the next day. evaporation? Although if it is low tide between 2 am and 3 am then ...

organic chemistry--please help me!!!
This is related to an interesting reaction that has been popular as a lab practical experiment in various forms for the last 20+ years. Addition reaction of the acid with the alkene will produce 4 methylcyclohexanol and 3 methyl cyclohexanol, both as cis/trans mixtures. These ...

geography
It is most clear at Greenwich where there is a brass line on the ground to show which is west and east.

Chem
Any suggestions? This is not hard.

Chem
You do not state the physical state of the oxygen. If it is a gas jar of oxygen then this site might help. It is a good site for MSD information. http://msds.chem.ox.ac.uk/OX/oxygen.html

Chem
Distillation?

chemistry
Do you mean diborane? Not the usual method to make NaBH4! 2NaH + B2H6 -> 2NaBH4 work out the number of moles of each of the two starting materials so to find out if one is a limiting reagent. Then base your theoretical yield on the limiting reagent. Once you have the ...

Quantitative Methods
It is not that helpful to post a reference to a problem in a text book to which there is no access. You are also unlikely to get answers to a multiple part problem unless you are asking for comment on your own answers.

chemistry -- help
I am not exactly sure what 'with few amounts..' means. The sugar drops out of solution quite rapidly from the supersaturated solution. I suspect that if you add a small amount of solid sugar to to a large container of supersaturated solution then you end up with a ...

Chemistry
It depends on what the 'products' are. Excess acetic acid (ethanoic acid) is usally removed from a material by shaking the mixture (that has been taken up in an organic solvent) with an aqueous carbonate solution or a NaOH solution. Depending on the scale, how much ...

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