Wednesday
April 23, 2014

Posts by andy


Total # Posts: 803

SCIENCE?CHEMISTRY***
DR Bob, can you go thru the steps to work this out please.... how many grams of alcohol with a density of 0.900 g/cm ^3 (cm cubed) will have the same volume as 20.0g of mercury,with a density of 13.6 g/cm ^3 Do you have to find the volume of mercury first??? I know the answer ...

chemistry
thanks..andy

chemistry
The solubility of MnS was found to be 0.000963 g per 700 mL of water. Calculate the solubility product constant (Ksp) for MnS. MnS (s)=Mn2+ (aq) + S2- (aq)

chemistry
The solubility product constant (Ksp) for the dissolution of PbSO4 as represented by the chemical equation is 1.7x10-8. PbSO4 (s)= Pb2+ (aq) + SO42- (aq) Calculate the mass (g) of PbSO4 that dissolves in 1100 mL of water.

SCIENCE/CHEM
thanks so much....andy

SCIENCE/CHEM
Dr Bob Is it true that only TWO molecules of water are required to balance the equation for the reaction of HCL with Calcium Hydroxide.(calcium chloride is the other product....why??? Thanks andy

SCIENCE/CHEM
thanks.... andy

SCIENCE/CHEM
Dr BOB, Can you show me how to do the balanced equation please I am shocking at them Thanks AndyWhats the simple way to explain balancing equations so i get it please....because i am horrible at them... Thanks andy

SCIENCE/CHEM
the purity of zinc is to be determined by measuring the amount of hydrogen formed when a weighed sample of zinc reacts with an excess of HCL acid.the sample weighs 0.198 grams. what amount of hydrogen gas at STP will be obtained if the zinc is 100% pure? need a metric answer p...

SCIENCE/CHEM
thanks..... andy

SCIENCE/CHEM
the volume of a sample of gas is 650.ml at STP. what volumes will the sample occupy at 0.0degrees celsius and 950.torr??? is it 650.ml?

SCIENCE/CHEM
thanks so much ...andy

SCIENCE/CHEM
so 2 X4 ^2 = 32 so 32 is correct ....... thanks andy

SCIENCE/CHEM
thanks...andy

SCIENCE/CHEM
how many electrons can be contained in all orbitals with n=4??????

SCIENCE/CHEM
thanks ...will practice and practice and practice.....andy

SCIENCE/CHEM
I suck at balancing!!!! Sorry Dr BOb you will have to take me on a slow journey on this one....Thanks andy

SCIENCE/CHEM
when the following equation is balanced , what is the sum of the co-efficients? AL2(SO4)^3+Ca(OH)2-->Al(OH)3+CaSO4

science /chem
thanks so much....andy

science /chem
1.250X10^3 ....hows that???

science /chem
thanks I think I acn do that one now...Regards Andy

science /chem
1250.37986 rounded to four significant figures is ??????

SCIENCE/CHEM
thanks...... andy

SCIENCE/CHEM
aha....# of prot and electrons =35 same as atomic number. #of neutons=mass number - atomic number=44 neutrons... so 35 protons,44 neutrons and 35 electrons .....hows that???

SCIENCE/CHEM
does that narrow it down to 35 prot,79 neutrons and 35 electrons? Soory bit lost on electrons... Andy why was there two choices for mass number???

SCIENCE/CHEM
Bromine exists as a mix of bromine 79 and bromine 81 isotopes. an atom of bromine 79 contains: 35 prot.44.neutr.35 electrons 35 prot.and 35 electrons only 44 prot.44 elect and 35 neutr. 35 prot.79 neutr. and 35 electrons 79 protons 79 electrons and 35 neutr. which is correct p...

MATHS !!!
thanks..... andy

MATHS !!!
convert 3.22 mm into cm please

SCIENCE 1
Thanks so much I have always wondered

SCIENCE 1
Does a snails shell grow at the same rate as the snail?? HOW???

chemistry
Thanks Dr bob my brain hurts about this stuff as i try to memorise too much.... thanks for your advice and maybe one day it will all come clear and until then i am still waiting for my AHA...moment sorry till then i need help ....thats why god put brilliant and patient teacher...

chemistry
Dr bob can you help with my last question for tonights home work please A gas mixture consists of equal parts of methane(molecular weight 16.0) and argon (atomic weight40.0). if the partial pressure of argon is 26.6 kPa what is that of methane in the same units? 10.7 26.7 66.7...

maths
thanks so much

maths
which of the following statements is incorrect? 1 microlitre=10^-6 litres 1 megagram=10^6 grams 1 millimetre=10^3 metres 1 kilogram=10^3 grams 100 centimetres=1 metre thanks andy

CHEMISTRY
so its a trick question as the unwary would say that CH4 and Ar under ideal behavior would be the same and the answer would be 26.7....?? But its obviously worded to catch out the unwary about partial pressure questions? Finally i can rest and the answer is 66.7 NOT 26.7!!!!! ...

CHEMISTRY
ok so P ch4 = 13.67 kPa where do i go from there??

CHEMISTRY
a gas mixtuer consists of equal masses of methane(molecular weight 16.0) and argon (atomic weight 40.0) if the partial pressure of argon is 26.6 kPa, what is that of methane in the same units? 10.7 26.7 66.7 34.1 I am going with 26.7 Do you agree and why please Thanks Andy

CHEMISTRY
I am confused about this statement about water Which of the following is TRUE regarding water only covalent bonds are broken when ice melts (dont think so) all of the staements (A-D) are false energy must be given off in order to break down the crystal lattice of ice to a liqu...

biology
Non vasculaar plants are those that dont use a vascular system to transport fluids around the plant..such as moss Hope this helps

CHEMISTRY
although helium atoms do not combine to form He2 molecules is it fair to say that London dispersion forces (induced dipole forces)are what attract He atoms weakly to one another? The other choices are dipole-induced dipole forces Hydrogen bonding Ion-dipole forces dipole-dipol...

CHEMISTRY
Wow great!!! thanks very muchyou are right when you look at the shape in the book...it actually becomes obvious Andy

CHEMISTRY
do you agree that HCL is the beast choice for a substance that has both dipersion forces and dipole-dipole forces ? The choices I have are : Br2 HCl H2 CO2 BCl3 HCL is the most sensible answer. Do you reckon so too? thanks andy

Chemistry
thank you so much for that wonderful chart Andy

Chemistry
That would be great if i could see the chart thanks Andy

Chemistry
Dr Bob Can you please confirm for me that only NH3 has a boiling point that does not fit the general trend from these choices NH3 PH3 SbH3 AsH3 many thanks andy I am picking NH3 because of the reason that the larger the compound the greater the boiling point Am I right with my...

science/chemistry
thanks andy

science/chemistry
Dr Bob Although helium atoms do not combine to form He2 molecules. is it true to say that He atoms are weakly attracted to one another from London dispersion forces (induced dipole forces) or is there another force at play? It cant be Hydrogen bonding(there is no hydrogen here...

CHEMISTRY!!/science
A mixture of CO2 and an unknown gas was allowed to effuse from a container. The carbon dioxide took 1.25 times longer than the unknown gas to escape.Which of the following gases could the unknown one be Choices A: Cl2 B: CO C: HCl D: H2 E: SO2 I am going B for this reason: CO...

science/chemistry
Oh I see now that you explained it that way!!!! OOPS....sorry yes I took a stab in the dark.....One day I may get this stuff....its going to be a long trip....How do YOU remember all this??? My heads about to explode and I am too young to die!!!!!!!!

science/chemistry
Aha its actually A??? Correct???

CHEMISTRY!!
Which of the following is NOT a postulate of the kinetic molecular theory? A; the average kinetic energy of the particles is directly proportional to the absolute temp. B;the forces of attraction and repulsion between the particles are insignificant C:the moving particles unde...

CHEMISTRY!!
Can someone check my answer please: Magnesium metal(0.100 mol)and a volume of aqueous HCL that contains 0.500 mol are combined to react to completion. how many litres of hydrogen gas (measured at STP) are produced choices: 4.42 11.1 22.7 2.27 5.53 I like 2.27... Is this right?...

CHEMISTRY!!
I believe that you are right due to the conversion difference and the fact that none of the other answer are even remotly close !!! Thanks DR BOB

CHEMISTRY!!
Calculate the mass in grams of 2.74L of CO gas at 33 degrees celcius and 126.0 kPa I got 3.75 grams Is this right please Thanks

CHEMISTRY
Thanks Dr Bob You rock!!!! Andy

CHEMISTRY
Dr Bob Can you confirm please Given a cylinder of fixed volume filled with one mole of Ar gas,which of the following is CORRECT? (assume that all gases obey the ideal gas laws) A: if the cylinder temp. is changed from 20 to 25 deg.C the pressure will double B:a cylinder of ide...

science
For the following reaction if the reaction temperature was increased would the equilibrium shift to the right or the left,not shift at all,or you cant answer the question because Keq is not given? 2SO3(g)<-->2SO2(g)+O2(g)..(deltaH degrees =198kj) Why???

chemistry
Thanks DR BOB, You had me worried for a second there!! Thanks for all your great help on this one Regards Andy

chemistry
Doess this mean I fluked the write answer?? Could you write it out as I have above please with your logical answers so I can go away and study if we are right..I am never comfortable not knowing I have the right workings Thanks andy

chemistry
Can you please check if I came up with the right answer for this please. A 4.30L container had 55.10 moles of N2O4 added to it. When equilibrium was established the concentration of N2O4 was found to be 1.69M.What is the Kc for the following reaction? N2O4(g)<-->2NO2(g) ...

chemistry
is the above equation balanced? 3CIO2-(aq)<-->2CIO3-(aq)+cl- if not how do you balance it (I suck at this) thanks Andy

chemistry
Dr Bob NO I dont know how too do Keq.. Can you give me some starts on this problem please.Thanks andy

chemistry
Write the equilibrium expression Qc for the following: 3CIO2-(aq)<-->2CIO3-(aq)+Cl-(aq) Choices: 3[CIO2-]/2[CIO3-][Cl-] 2[CIO3-][Cl-]/3[CIO2-] [CIO2-]^3/[CIO3-]^2[Cl-] [CIO3-]^2[Cl-]/[CIO2-]^3 I dont even know where to start with this one can you help please. Thanks andy

chemistry
DR BOB Can you check my answer at Monday may 10 2010 at 7:12 pm at Chemistry -andy(Page 2) I think I may have got it !!! Thanks andy

Intermediate Algebra
thanks

Intermediate Algebra
How would I figure out this math problem? (a video game was $49.95. The price dropped to $45.50. what was the percent of decrease.)

science
Dr bob, can you check my reply to chem question from andy thanx

chemistry
Dr bob, can you check out my theory on previous post....thanx Andy

chemistry
for the equilibrium H2+CO2<-->H2O+CO Kc=3.18 at 1106K. if each of the four species was initially present at 3.000M calculate the equilibrium concentration of the CO at this temperature..... OK I can get as far as equilibrium (final) H2O=3.000-x CO=3.000-xx H2=3.000+x CO2...

chemistry
Thanks Dr Bob, I am horrible at algebra.... But since reading your reasoning I have now got ammunition to be able to reason out the answer....I will try harder and study more.. Thanks for all your advice it was great Andy

chemistry
Dr BOB, How this (3+0.844)^2/(3-0.844)^2=3.18(rounded) sqrt(3.18)=1.7832 So there fore answer=0.844 which is one of the answers! Am I on the right track? Andy

chemistry
DR Bob, If I plug in 0.01 for x then the answer is (3.000+0.01)times(3.000+0.01)divided by (3.000-0.01)times(3.000-0.01)answer according to my calculator says 9.0601.....ok how does that relate to the answer??am I to keep guessing what X isuntill I get the answer? or is there ...

chemistry
DR bob I got that far no probs...But dont know how to do the last bit could you expand please Thanks andy

chemistry
For the equilibrium H2(g)+CO2(g)<-->H2O(g)+CO(g) Kc=3.18 at 1106 K.If each of the four species was initially present at a concentration of 3.000M,Calculate the equilibrium concentration of the CO (g) at this temperature. Choices 0.844 3.268 3.844 3.460 2.156 Thanks anyon...

Chemisty 11 U
Determin the number of oxygen atmos in 1.75kg of potassium sulfate.

Chemisty 11 U
where??

Chemisty 11 U
Determin the number of oxygen atmos in 1.75kg of potassium sulfate.

Chemisty 11 U
Determin the number of oxygen atmos in 1.75kg of potassium sulfate.

Chemisty 11
thank you

Chemisty 11
Why is it important to use the correct salt-sand mix on highways during storms? Help please this is for my Chemisty Project

physics helpppp
Figure 10-35a shows a disk that can rotate about an axis at a radial distance h from the center of the disk. Figure 10-35b gives the rotational inertia I of the disk about the axis as a function of that distance h, from the center out to the edge of the disk. The scale on the ...

physics please help
Find Beta and Gamma for an electron that has a kinetic energy of 6.00 keV. gamma = KE/MoC^2 + 1 Beta = 1/gamma^2 + 1 gamma = 1.011723381 Beta = 1.9769592 I am getting gamma right but I am getting Beta wrong what I'm I doing wrong??

physics
Find Beta and Gamma for an electron that has a kinetic energy of 6.00 keV. â? gamma = KE/MoC^2 + 1 Beta = 1/gamma^2 + 1 gamma = 1.011723381 Beta = 1.9769592 I got gamma correct but my answer but im getting gamma incorrect can anyone explain what could be wrong

physics
Spaceship I, which contains students taking a physics exam, approaches Earth with a speed of 0.640 c, while spaceship II, which contains instructors proctoring the exam, moves away from Earth at 0.280 c, as in Figure P26.27. If the instructors in spaceship II stop the exam aft...

physics
Spaceship I, which contains students taking a physics exam, approaches Earth with a speed of 0.640 c, while spaceship II, which contains instructors proctoring the exam, moves away from Earth at 0.280 c, as in Figure P26.27. If the instructors in spaceship II stop the exam aft...

physics
Can a person, in principle, travel from Earth to the galactic center (which is about 2.3e4 lightyears distant) in a normal lifetime? Explain, using either time-dilation or length contraction arguments. If they want to make the trip in 24 y what distance would the person travel...

physics
drwls you are awesome!!

physics
The average lifetime of muons at rest is 2.20 us. A laboratory measurement on muons traveling in a beam emerging from a particle accelerator yields an average muon lifetime of 19.668 us. What is the speed of the muons in the laboratory? u=((1-(2.2e-6/19.688e-6)^2))^(1/2)=0.994...

chemistry
When CO(g) (38.11 grams) and 96.48 grams of Cl2(g) in a 140.0 L reaction vessel at 782.0 K are allowed to come to equilibrium the mixture contains 0.4080 mol of Cl2CO(g). What is the equilibrium concentration (mol/L) of CO(g)? CO(g)+Cl2(g) = Cl2CO(g) Can anyone help with the s...

chemistry
When CS2(g) (545.0 grams) and 57.71 grams of H2(g) in a 200.0 L reaction vessel at 961.0 K are allowed to come to equilibrium the mixture contains 2.447 mol of CH4(g). What concentration (mol/L) of CS2(g) reacted? Molar Mass CS2(g) 76.15 H2(g) 2.016 CH4(g) 16.043 H2S(g) 34.086...

physics
is rest mass energy 9.11e-31 * (3e8)^2 ?? and do I need to convert from J to ev to KeV? Thanks for the help

physics
How much work must be done to increase the speed of an electron from 0.200c to 0.210c? In (MeV)

physics
A.An observer moving at a speed of 0.810 c relative to a rod measures its length to be 2.00 m and sees its length to be oriented at 30.0 degrees with respect to the direction of motion. What is the proper length of the rod? B.What is the orientation angle in a reference frame ...

chemistry
The value of the equilibrium constant (Kc) as represented by the first chemical equation is 2.70 x 10-3 at 1200 K. Calculate the value of the equilibrium constant (Kc) for the second equation at the same temperature. Express answer in scientific notation. F2(g) = 2F(g) 2F(g) =...

chemistry
How do you figure out the answer for the reverse reaction? At 350 K the value of Kp for the equilibrium represented by the balanced equation is 2.87 x 10-2. Calculate the value of Kc for the reverse reaction at the same temperature. Express answer in scientific notation. 2NOBr...

biology
1. Some photosynthetic bacteria are able to harvest 900-nanometer light (4 points). A. What is the energy in kilocalories of a mole (an einstein) of 900-nanometer light? B. What is the minimum number of 900 nanometer photons needed to form one molecule of ATP from ADP and inor...

chemistry
Calculate the value of the equilibrium constant (Kp) for the reaction shown, if F(g) was found to be 96.80 % decomposed at 1000 K when its initial pressure was 4.638 atm. The initial pressure of the reaction products is 0 atm. 2F(g) = F2(g)

chemistry
On this problem I keep getting the wrong answer. I am subtracting the initial concentration of Cl2 by the equilibrium concentration then using the difference to subtract for the rest using the mole ratios. Then i used the keq constant equation of concentration of products over...

chemistry
I keep getting the wrong answer for this one can someone help. The initial concentration for the compounds involved in the reaction displayed were determined to be [NOCl(g)] = 0.1738 mol/L, [NO(g)] = 0.1991 mol/L, [Cl2(g)] = 0.000005938 mol/L. Calculate the value of the equili...

chemistry
I was having trouble with this problem. initial pressure for the compounds involved in the reaction displayed were determined to be P(CO(g)) = 0.5794 atm, P(H2O(g)) = 0.5662 atm, P(CO2(g)) = 0.7950 atm, P(H2(g)) = 0.2754 atm. Calculate the value of the equilibrium constant (K...

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