change

  1. R

    CO2 solubility and temperature change and climate

    I am a cycles researcher. There are cycles in climate. There are correlations between atmospheric CO2 and temperature. The connection is not as many people make out. I am not a chemist although I did some chemistry study a very long time ago. I have been researching the relationship between...
  2. P

    Change atomic model

    Atomic model(another way to understand atomic model) can connect together by one way as direction. Just counting electronic and atom as frame 1+1=2. (Energy means the group of atomic model). So when we separate atom and electronic, then the one way is changed into another direction. So we can...
  3. R

    Determine Enthalpy Change

    Please help me answer and understand this: Chloroform, CHCl3, is formed by the following reaction: CH4(g) + 3 Cl2(g) → 3 HCl(g) + CHCl3 (g) Determine the enthalpy change for this reaction (ΔH°rxn), using the following: enthalpy of formation of CHCl3 (g), ΔH°f = – 103.1 kJ/mol...
  4. M

    Chromatography, Change of efficency required to double the resolution?

    I've stumbled upon a problem which I think i've misunderstood. The question at hand is "How do you change the efficency(or number of "bottoms" as its called in swedish) to double the resolution?" Naturally, i thought it was just to expand the formula by multiplying by 2 on both sides of the...
  5. U

    inorganic salt phase change materials

    hello new here . i have moved this post from the new user section. hope this is ok. please tell me if it isn't! my question relates to using sodium sulphate as a PCM i am using the decahydrate form at the moment but the anhydous form is a lot cheaper in bulk. is there a way to convert it to the...
  6. U

    salt phase change materials

    hello new here . my question relates to using sodium sulphate as a PCM i am using the decahydrate form at the moment but the anhydous form is a lot cheaper in bulk. is there a way to convert it to the decahydrate form easily? one report says just leave it in the damp air,but can i just add...
  7. F

    Is there any change in mass as the electron changes energy levels.

    Does anything happen to the electron, as it changes energy levels, does its mass increase, or decrease, or velocity speed up, or slow down.? The electron will speed up when its away from the nucleus, when its in a higher shell like shell level 3. But is there anything like a visible sign that...
  8. F

    Is it known to science why electron energy levels change, as atoms become molecules,

    Is it known to science why electron energy levels change, as atoms become molecules, or why electron voltage requirement changes when the electron is from the nucleus in higher shell levels. So can it just he observed that electrons need a certain electron voltage to move to higher shell...
  9. T

    How does the electromotive force effect the electron for the band gap to change, to i

    How does the electromotive force effect the electron for the band gap to change, to increase, and decrease.? someone told me on a forum, "It takes energy, either in the form of light, heat or electromotive force to move electrons from one energy level to a higher one, while they will typically...
  10. J

    Change in Enthalpy

    Using the balanced equation for the heat of formation of water and the following thermonuclear equation, calculate the amount of heat released when 27.9 grams of C(s) is incompletely combusted to give CO(g). C(s) + H2O(g) → CO(g) + H2(g) ΔH°rxn = 131.3 kj/mol I think that I know...
  11. JasonHerbalExt

    what change will increase the quantity of CO(g) for the reaction at equilibrium?

    If the reaction is at equilibrium with excess C(s) remaining, what change will increase the quantity of CO(g) for the reaction at equilibrium? I Adding C(s) II Increasing the temperature III Increasing the pressure (A) I only (B) III only (C) I, II, and III (D) None of these
  12. M

    Hydrogen Atom : Change in Energy & Wave Function

    If the proton in hydrogen is replaced by a positron-how does it effect Energy and Wave Function ? Help please !
  13. D

    entropy change adiabatic expansion

    Hello all, this may be a silly question , but for some reason I can't seem to find an explanation anywhere... When an adiabatic process is reversible, why is the entropy=0 (which is not true for an irreversible) using equation, I understand why this is true (since Q=0) but conceptually I'm...
  14. S

    Figuring out enthalpy change when NaNO3 is dissolved in water

    [SOLVED] When 15.3g of sodium nitrate, NaNO3, was dissolved in water in a constant-pressure calorimeter, the temperature fell from 25.00 degrees Celsius to 21.56 degrees Celsius. If the heat capacity of the solution and the calorimeter is 1071 Joules per degrees Celsius, what is the...
  15. S

    Calculating Standard Enthalpy Change

    Hello! :) I have honestly no idea on how to approach this seemingly easy question, can somebody please provide me with some assistance? I'm adding the enthalpy values up and then entering that as the answer (along with numerous other attempts that have been unsuccessful) and I just don't know...
  16. T

    Simple Change in Molar Volume Question

    Hi, The question states: "Calculate the change in molar volume for the reaction of corundum (Al_2O_3) in liquid water to from gibbsite (Al(OH)_3). My question would be, is when I look at the table that was provided, (Al(OH)_3) is listed in aquas form but does not list a molar volume. But if I...
  17. S

    Direction and Extent of Chemical Change Question

    Can a mixture of 2.2 mol O2, 3.6 mol SO2, and 1.8 mol SO3 be maintained indefinitely in a 7.2 L flask at a temperature at which Kc = 100 in this reaction? 2SO2(g) + O2(g) <-> 2SO3(g) I found the Reaction Quotient and it was less than the equilibrium constant of 100. Q<K so the...
  18. C

    Calculate volume of HCl needed to change buffer pH by 1 unit???

    How do you calculate the amount of HCl needed to change the pH of a NH3/NH4+ buffer by 1 unit? There was 100mL of NH3 2M and 10.698g of NH4 0.5M and then this was mixed with 400mL of water to make 500mL buffer solution. Only 80mL of this was used for each trial. HCl was 1M. Starting pH was...
  19. P

    Adiabatic entropy change

    For an adiabatic process dQ=0, there is no heat exchange with the surroundings, therefore dS(surroundings)=0. For expansion of an ideal gas, so the dS(total) must either be = 0 (in the case of a reversible change) or it must increase (second law). In the case of the dS(total) increasing the...
  20. H

    Need help with a heat change problem

    A 300 gram piece of iron (you can look up the specific heat capacity of iron) is heated to 200ºC in an oven and “instantly” transferred into 600 grams of water at 5ºC. Assuming that all of the heat from the hot metal is transferred to the cold water, what will the final temperature be? Show all...