Concentration Definition and 550 Threads

Ok hydrogen ion gradient drives ATP synthase. In secondary active transport the preexisting concentration gradient drives the molecules. My question is what do they mean when they say concentration gradient provides energy to do this. Is it the movement of ions like hyrdogen from high to low...

How does one calculate the intrinsic carrier concentration Ni for silicon as a function of temperature? I know the equation ni^2 = Nc*Nv exp(-Eg/kT) can be used, but then another equation is needed to find the energy band gap Eg. The effective density of states values Nc and Nv are well...

Homework Statement Is there any way to calculate a solution's concentration (mass percentage - that is, the percentage of the solute mass to the solution mass) just by knowing its index of refraction? If it helps, the solute is NaCl, so I know the molar mass of the solute. I also have the...

Homework Statement Show that concentration of a substance obeys the diffusion equation if the rate at which substance leaves a region is proportional to the concentration gradient. Homework Equations Diffusion equation: \nabla2\phi = (1/a) (d(phi)/dt) where Phi is a function of r, t...

Homework Statement Consider the reaction with the rate law, Rate = k[BrO3-][Br-][H+]2 By what factor does the rate change if the concentration of H+ is decreased by a factor of 3? Just put in the number as a whole number or fraction. Homework Equations The Attempt at a Solution...

Hello all, I am trying to revise over acids and bases before my exams, but there is one question I am stuck on, and I am not sure how to approach it. Any hints would be great ^^ "100mL of HCL of pH of 4.0 is mixed with 100mL of HCL of PH of 5.0. Whats the resulting pH of the solution...

Homework Statement trying to work out the answer for the temperature T from the equation... (1012)2=(2.8*1019)(1.04*1019)(T/300)3exp(-1.12/KT) Homework Equations the equation was derived from ni2=NcNv(T/300)3exp(-Eg/KT) The Attempt at a Solution Only simplified the equation to...

A tank contains 4000L of pure water. Brine that contains 30g of salt per liter of water is pumped into the tank at a rate of 25L/min. Show that the concentration of salt after t minutes (in grams per liter) is C(t) = 30t/160+t What happens to the concentration as t --> infinity lim C(t)=...

I have recorded cross sections of a surface layer on a substrate in a scanning electron microscope (SEM), and took EDX (energy dispersive x-ray spectroscopy) linescans across the layer. These are typically given in counts or cts per second. Now, I know the average thickness of the layer...

We know that Vmax depends on enzyme concentration since Vmax = k2[E] However, what I have trouble grasp is that why Km does not depend on enzyme concentration if Km is the substrate concentration where V = 1/2 Vmax. If you increase Vmax, shouldn't Km increase as well since it is dependent on...

iron(ii) can be determined by redox titration with a cerium (iv) solution. the oxidation reduced reaction is fe2+ + ce2+ = fe3+ + ce3+ what is the concentration of fe2+ if it requires 21.35mL of .3136 ce4+ to titrate a 10.00mL aliquot to the endpoint.

the question is at below. 320ml of 29wt% of ammonium hydroxide 1210ml of 31wt% of hydrogen peroxide 30190ml of water mixed together. What is the concentration of ammonium hydroxide and hydrogen peroxide now? Is there any reaction occurs between them?

Hi, I've been pondering over the properties of a beam of light and I'm curious if the concentration of photons in eg. a laser beam can be calculated. To elaborate on this question, let me ask if we can calculate the number of photons in a beam of light x distance long with a given cross...

Hello!.. I would like to ask something. How should I calculate the concentration of a solution?or how to set (by the use of calculation) concentration of a solution. We are about to start our research and we are assigned to set up concentration of a solution but we don't know to do it. We...

Homework Statement Calculate the concentration of Hg+2 at equilibrium in a solution that is initially 0.10M in Hg+2 and 0.50M in CN-. K instab for [Hg(CN)4]2- = 3.0 x 10 -42 Homework Equations K instab The Attempt at a Solution [Hg(CN)4]2- --> Hg2+ + 4 CN- Initial Conc...

Hi all: I'm working in a air pollutant level sensing system, to measure the common air pollutants and their level. I begun with this some months ago (In fact I've taken the others work's in my hands), and used electrochemical gas sensors for low ppm sensing (Up to 50ppm) and with 0.1ppm...

Homework Statement Calculate the [H3O+] concentration (in M) in a 0.1 M aqueous solution of NH3. [Kb = 1.8 x 10–5 ] (a) 7.5 x 10–12 M (c) 1.8 x 10–6 M (b) 3.0 x 10–10 M (d) 1.3 x 10–3 M Homework Equations ΔTb = Kb x m The Attempt at a Solution So... I'm kind of at a loss here...

Homework Statement calculate the formate ion concentration and pH of a solution that is 0.05m in formic acid (HCOOH;Ka=1.8x10^-4) and 0.10M in HNO3. hey guys just wondering how the equation goes?? like this?? HCOOH + HNO3>>?

Should I take a concentration with my physics major? What are the benefits? I'm interested in astrophysics, should I take a materials science or astronomy concentration?

sorry i already made a similar topic before but i didnt get any response so i decided to be more specific. i am an applied physics major freshman. i have to pick a concentration of studies but i don't know what to pick. what are some possible career paths for dual majoring in applied...

A "concentration" degree vs a "regular" degree Good afternoon everyone. I'm new here and it's great to be here. I have a very large interest in Physics and plan on getting a degree in said field. I do have one big question; Is there a big difference between having a BS in Physics and a BS in...

Homework Statement Calculate the molarity and mole fraction of acetone in a 1.00 m solution of acetone, CH3COCH3 (d=0.788 g/mL) in ethanol, C2H5OH (d=0.789 g/mL). Assume that the volumes of acetone and ethanol add. Homework Equations The Attempt at a Solution I'm not sure if I'm...

Homework Statement In this experiment you will find the ionization constant for ammonia, a weak base. I have completed the experiment, and have the following: Initial concentration of NH3: 3.708mol/L Initial pH of NH3: 10.26 Homework Equations NH3(aq) + H2O(l) <--> NH4+(aq) +...

1. COCl2(g) D CO(g) + Cl2(g) Kp = 6.8 x 10-9 at 100oC What will be the equilibrium concentrations of all 3 gases if 1.0 atm of phosgene (COCl2) is placed into 5.0L reaction vessel? The answer is [COCl2]eq = 0.033M [CO]eq = [Cl2]eq = 2.69 x 10-10M I don't get how the second one...

Homework Statement At 300 K, kp = 1.5 x 1018 for the reaction 3NO --> N2O + NO2 If 0.030 mol of NO were placed in a 1.00 L vessel and and equilibrium was established, find the equilibrium concentrations of NO, N2O and NO2. Homework Equations The Attempt at a Solution First, I...

Is it possible to find out the relative concentration of c02 by looking at the emission or absorption from a hot gas, T = 1000K, containing among other C02? What I want to find out is if the emission depends linearly on the concentration. (in the IR region) What theoretically equations may I...

Hi! In my lab we're preparing a toxicity bioassay using nitrate (NO3-) as the test toxicant. The tests we're doing are range-finding tests, to help determine the lethal concentration (LC50) for that species with nitrate. We are following the lead of another work...

Homework Statement hey guys I've got a problem, could you tell us where i went wrong Lithopone is a brilliant white pigment used in water-based interior paints. It is a mixture of barium sulfate and zinc sulfide produced by the reaction BaS(aq) + ZnSO4(aq) ZnS(s) + BaSO4(s) What mass of...

Homework Statement You are provided with a solution of hydrogen peroxide which is known to be approximately ‘100-volume’. Plan two experiments that would enable you to determine the exact concentration of H2O2 in mol dm-3, in this solution Homework Equations 2H2O2 (aq)...

To determine the Fermi Energy for metals such as sodium, copper, gold, ect., one needs the Electron Concentration per cubic meter for the metal of interest. I am curious how this quantity can be determined. I referred to my physics textbooks and did search the Internet. However, the...

Homework Statement You are provided with a solution of hydrogen peroxide which is known to be approximately ‘100-volume’. Plan two experiments that would enable you to determine the exact concentration of H2O2 in mol dm-3, in this solution. One of your experiments should involve a redox...

Homework Statement CH4 (g) + H2O (g) <- -> CO (g) + 3 H2 (g) .2 M CH4 and .2 M H2O are added to an empty 4 L sealed vessel at 1400 K. When equilibrium is established, the concentration of H2 is .444 M. Calculate Kc... which I did and got 4.8 which is the given answer. The real problem I...

Homework Statement Insects do not have lungs as we do, nor do they breathe through their mouths. Instead, they have a system of tiny tubes, called tracheae, through which oxygen diffuses into their bodies. The tracheae begin at the surface of the insect's body and penetrate into the...

Homework Statement Find the required mass of Al2(SO4)3.18H2O (molar mass = 666 g/mol) to prepare 50 mL of an aqueous solution, concentration = 40 mg of Al3+ per mL The Attempt at a Solution 0.04 grams of Al3+/1mL = x g / 50 mL x = 2g I think this is the required mass of Al3+, now I...

*urgent* Finding unknown acid concentration Homework Statement Construct an experimental procedure in in order to determine the unknown concentration of an acid. Be sure to describe the standardization process. Homework Equations The Attempt at a Solution I think a viable...

% by mass concentration Homework Statement An aqueous CaCL2 solution has a vapor pressure of 80.8mmHG at 50 degree C . The vapor pressure of pure water at this temperature is 92.6 mmHG . What is the concentration of CaCl2 in mass percent? Homework Equations % by mass = mass solute/mass...

% at. concentration unit? hi all i wonder if someone can help me to know about the concentration measurement unit (% at. ), what does that mean?? thanks

Homework Statement How many mL of 50.0% by mass HNO3 solution, with a density of 2.00 g/mL is required to make a 500 mL of a 2.00 M HNO3?Homework Equations initial Molarity X initial Volume = final Molarity X final VolumeThe Attempt at a Solution (50 g HNO3)(1 mL/2.00 g)(0.001 L/1 mL) =...

Homework Statement Hello. I have a lab procedure that I am supposed to write, and since my teacher is on a two-week sick leave and the substitute does not know anything, I seriously need some assistance. Please note that for the following problem, a titration is NOT allowed. It must be...

I solved an assignment problem and I came to the conclusion that the % ionization of a strong acid decreases as the initial concentration of the ionized acid is increased. I don't fully understand why this is..? Any clarification would be greatly appreciated! Thanks in advance!

Homework Statement If 0.12 g of magnesium hydroxide Mg(OH)2 is dissolved in sufficient water to make 500. mL of solution, what is the hydronium ion concentration in the solution? (Assume that all of the magnesium hydroxide dissolves.) Homework Equations pH = -log [OH-] pOH = -log...

Homework Statement The phosphoric acid in a 100.00 mL sample of a cola drink was titrated with 0.1029 M NaOH. The first equivalence point was detected after 13.34 mL of base added, and the scond equivalence point after 28.24 mL. Calculate the concentration of H2PO4- in mol/L. (Hint: if only...

lmax or 1max ?? Homework Statement I have a graph of concentration vs Absorbance like below, for PNP. http://img512.imageshack.us/img512/2614/pnpgraphexfa7.jpg problem is that I have to find the unknown concentration, so I use the graph to determine that. The equation to find it is...

I was wondering if someone could help me understand how to measure different concentrations of dye in water. My experiment is to test out different concentrations of dye, that will be able to change the color of a flower. I didnt want to use the simple way of putting 1 drop, 2 drop, etc...in...

Homework Statement suppose that for a 10 mL sample of Ba(OH)2 solution, the mass of the cubicle with precipitate is 17.539g and the mass of the empty cubicle is 17.410g. calculate the concentration of the Ba(OH)2 solution from this data. Homework Equations The Attempt at a Solution

Homework Statement given a 10.0mL sample of Ba(OH)2 solution, calculate the concentration of the solution if it took 7.85mL of a .102 M H2SO4 to reach the equivalence point Homework Equations The Attempt at a Solution

Do any of you have experience with medication designed to increase concentration, directly or indirectly? I've continually pondered if this is something I should be seriously interested in. Anti-depressants have taunted me for many years, but I've managed to get by without them out of fear of...

I am performing an experiment where I am spiking my product with various % of CTAB. I have made stock solution of 2% (w/v) CTAB in 40 mM NaCl. I also need to make sure that I maintain the NaCl conentration at 40 mM. The product that the stock solution is being added to doesn't have any NaCl...

Homework Statement 6CO2 + 6 H2O → C6H12O6 + 6 O2 Now suppose the above reaction is allowed to proceed in both directions, and has reached equilibrium. How would increasing the concentration of oxygen change the concentrations of carbon dioxide and sugar? Homework Equations The Attempt at a...

Homework Statement A 20.00 ml stock sample of HBr is diluted to 50 mL. If 18.76 ml of 0.1345 M KOH was required to reach the equivalence point, what is the concentration of the stock HBr solution? Homework Equations KOH + HBr --> KBr + H20 M = conc. = mol./L n = V * conc. The...