Thursday
April 17, 2014

Posts by GK


Total # Posts: 644

Chemistry
This question has already been posted and answered, but I have a comment on the last part. The reason the spectral color lines are different for each element is that the photons produced by the dropping of electrons to lower energy levels within an atom are different for each ...

Chemistry
1. A flame heats the sample and may produce a flame color that helps us detect the presence of a certain element. Some elements cause the flame to glow a certain color which tells us that element is present in the sample. For example, a very bright yellow-orange flame color te...

Chemistry
1. The weight loss from 45.850g to 45.351g is the mass of oxygen, O2, gas released. The molar mass of O2 is 16.00x2 = 32.00g. This information should enable you get the moles of O2. 2. The volume of O2 = volume of water displaced. volume = mass/density. The density of water is...

physics
Electrical potential is the force experienced by a unit test charge at a particular point. In this case that potential on the test charge is generated by the positive and the negative charges placed in the two corners of the square. There are two possible configurations for th...

physics
To get the coordinates of each point you can use: (x1, y1) ---> x1=r1*cosA, y1=r1*sinA (r1 = 1.2km, A = 33deg) (x2, y2) ---> x2=r2*cosB, y2=r2*sinB (r2=2.0km, B = 75deg) The displacement is: d = sqrt[(x2-x1)^2 + (y2-y1)^2] The direction of the resultant, angle C is: C = ...

Chemistry
The graph of volume v. pressure should be a hyperbola since the volume and pressure of a gas vary inversely. However a small variation in pressure (i. e. 100cm H2O / 13.55 H2O/cmHg=7.4 cm of mercury which you have) would produce a near straight line with a negative slope. You ...

Physics
The velocity of the particle increases by a constant 5 m/s each second in the same direction. If we graph velocity v. time, we get a straight line with a positive slope. This line goes through the origin.

Chemistry
This question has already been answered. Enough hints have been given in that answer to complete it yourself. The assistance provided here is designed to help you learn enough to answer your own questions.

Chemistry
The vocabulary and symbols in this question are covered in any chemistry textbook with many examples. You should look them over.

Chemistry
The number of neutrons is: (mass number) - (atomic number) The mass number of the most common isotope of phosphorus is 31 (the rounded off atomic mass). I will let you look up the atomic number and do the subtraction.

Chemistry
The question is asking you (in a confusing way) to compare ionic bonds to INTERMOLECULAR attractions (attractions between neighboring molecules). The answer to that should not be much of a challenge. Consider the melting point of an ionic solid like sodium chloride to a molecu...

Chemistry
The least common multiple of 3 and 2 is 3x2=6 For each of the two elements, valence x subscript = 6 Based on that, the formula would be A2B3

chemistry
1. Since Zn is higher on the activity series than lead, the reaction would be: Zn(s) + Pb(NO3)2(aq) ---> ZnCl2(aq) + Pb(s) The zinc container would dissolve displacing Pb from the solution. Not a good choice of container. 2. Ag(s) + PbSO4(aq) ---> No reaction (Ag is lowe...

chemistry
I think I have seen these questions before. The net ionic equations look OK. The following are comments on the explanations: #1) OK #2) There fewer ions in the products (not reactants) which accounts for the decrease in electrical conductivity. #3) We start with one ion (Cu++)...

chemistry
This is not a chemistry question and we don't have access to page 86 of the unnamed textbook. The best advice is offered right in the question: Read the Bead Bar Consultant Information .... etc.

Chemistry
The equation I would set up based on the information given is: 2.56g Benz. Acid /100cm^3 water = 1.00g Benz. Acid / x cm^3 Without the units, 2.56 /100 = 1.00 / x Solve the above equation for "x" to get the minimum volume of water in cm^3 that would be needed to diss...

Chemistry
The solid must have high solubility at high temperature and much lower solubility at low temperature in the solvent or mixture of solvents chosen. The solid is dissolved at high temperature in the least volume of solvent, then cooled off. Unless the solution becomes supersatur...

Chemistry
The salt contains the conjugate base or acid of the corresponding acid or base on the list. Since most buffers are combinations of a weak acid and its conjugate base, or a weak base and its conjugate acid, the combination of the salt and the related acid or base make a buffer ...

Chemistry
Here are the two partial chemical equations with one formula for you to fill in in each one: Please note: *SO2 in a water solution is equivalent to sulfurous acid, H2SO3 -------------------- NaOH + HBr ---> NaBr + ______ 2NaOH + SO2 ---> Na2SO3 + ______

chemistry
(a) Coefficients represent molecules, or formula units, or moles, depending on the situation. (b) Removing air from a sealed container reduces the pressure inside it. How this affects the container, depends on the strength and rigidity of the container. (c) Polar solvents diss...

chemistry
multiply the 5 moles of zinc by the factor: (1.00/0.85)

chemistry
The reaction is: Zn + 2HCl --> ZnCl2 + H2 1 mole of any gas at STP is 22.4 L 112L of H2 / 22.4 L/mol = 5 moles H2 (5 mol H2)(1 mol Zn / 1 mol H2) = 5 moles of Zn The above relationship assumes that the reaction is 100% efficient. Since the reaction is only 85% efficient, MO...

chemistry
Kinetic energy for a single molecule is Ek=(1/2)mv^2 [m = molecular mass, v = molecular velocity] The average of all the individual molecular kinetic energies is what you are asking for. The temperature of a substance is proportional to the average molecular kinetic energy: (1...

chemistry
When you have gases at the same temperature and pressure, the volume ratio is equal to the mole ratio. The ratio of the coefficients in the chemical equation can be used as mole ratios OR volume ratios: (11L CS2)(3 L O2 / 1 L CS2) = 33 L O2 *needed* Since only 18 L O2 are *ava...

chemistry
What 2 to 1 ratio? The reaction is: P4+6H2-->4PH3. The limiting reagent is the reactant that you don't have enough of. Read my response to your question more carefully.

chemistry
Convert grams of phosphorus to moles of P4. Do likewise for grams of hydrogen, H2. To convert grams to moles you divide grams by the formula mass of that substance. The mole ratio of H2 reacting with P4 is 6/1. If the number of moles of H2 is 6 times (or greater) the moles of ...

Chemistry
moles OH- = (liters)(molarity) (0.115 mol NaOH/L)(0.03383L) = 3.89x10-3 mol OH- used to reach the end point Moles acid = moles OH- moles of acid neutralized = 3.89x10-3 mol 0.288 g acid/0.03383L = 8.513g/L (8.513g/L)/(0.115 mol/L) = ________g/mole

Chemistry
C2H2 + O2 ---> CO2 + H2O (assuming complete oxidation) H-C---C-CH(CH3-CH3 + H2 ---> 3-methylbutene or 2-methylbutane, depending on the degree of hydrogenation (reduction) CH3CH2Cl + NaOH ---> NaCl + _____?

chemistry boiiii
To find the number of moles, you divide the number of grams by the formula mass expressed in grams/mole: #moles = #grams / (formula mass)

chemistry
1 mole of CaO = 40.08 + 16.00 = 56.08g/mol 1 mol Hg = 200.6 g/mol (a) Convert 36.0 gHg to moles: (36.0gHg)/200.6gHg/molHg = 0.1795 mol Hg (b) It takes 4 mol CaO to produce 4 moles Hg, so.... (0.1795 mol Hg)(4 mol CaO / 4 mol Hg) = 0.1795 mol CaO (c) Convert 0.1795 mol CaO to g...

chemistry
(a) Look up the molar mass of Fe (= the atomic mass of Fe labeled "gFe/mol") (b) Divide16.7gFe by (a) to get moles of Fe (c) Multiply (b) by 2molFe2O3/4molFe (or 2/4) to get moles of Fe2O3 produced. (d) multiply (c) by the formula mass of Fe2O3* *To find the formula ...

chemistry
The metal composition of the electrodes doesn't matter as far as generating H2 and O2 gases initially. However, it is desirable for the composition of the two electrodes to remain constant so that their performance will not change during electrolysis. Platinum works very w...

Chemistry
Yes, melting ice is a physical change.

Chemistry
All oxidations are exothermic

chemistry - please help!
#1) Your answer is OK. It can be rewritten as 1.201x10^24 carbon atoms. #2) If you have 3.67 mol H2SO4, mols of hydrogen=(3.67)(2)=? mols of sulfur=(3.67)(1)=? mols of oxygen=(3.67)(4)=? Multiply each of the answers above by Avogadro's number, 6.02x10^23.

chemistry
When an electron moves closer to the nucleus, its potential energy decreases.

chemistry
Each electrode defines a half cell. Two half cells make up a complete electrochemical cell. The assignment of 0.00 volts for the hydrogen electrode potential is arbitrary. It was chosen because it is easy to construct, it behaves in a consistent, reproducible manner, and it di...

chemistry
This does not look like a complete question. How many grams of Fe2O3 are there?

Chemistry
Limestone can be heated in a furnace to convert it to quicklime which can be mixed with water to make lime (calcium hydroxide). Calcium hydroxide cam be mixed with sand and water to make lime mortar. Cement, which contains lime and other ingredients can also be used to make mo...

Chemistry
Write rate law expressions? 2NOCl(g) --> 2NO(g) + Cl2(g) rate=k[NOCl]^2 based on the Law of Mass Action. That is not necessarily the actual rate law, which must be determined by experiment. The effect of pressure depends on how the pressure is increased. IF it is increased ...

chemistry
a) [Ne] 3s^2, 3p^4 shows (2+4)=6 valence electrons. That is Group VI (O, S, etc.) in the "p-block" (last 6 columns) b) [Kr] 4d^10, 5s^2, 5p^2 shows (2+2)=4 valence electrons, Group IV (C, Si, etc.) in the "p-block" (c) [Xe] 4f^14, 5d^10, 6s^2, 6p^5, 7 valen...

Science
Atmospheric conditions are also called weather.

chemistry
Na: 1s^2, 2s^2, 2p^6, 3s^1 or, Na: [Ne] 3s^1 Sr: 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^10, 4p^6, 5s^2 or, Sr: [Kr] 5s^2 P: 1s^2, 2s^2, 2p^6, 3s^2, 3p^3 or, P: [Ne] 3s^2, 3p^3

physics
That depends on the design of the machine. Any design will violate at least one law of thermodynamics (1st, 2nd, or 3rd). Having said that, most people think that it is the 1st or 2nd law that would have to be violated in designing a perpetual motion machine. The first law sta...

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