1. G

    Need help with calculating change in enthalpy

    I’ve got an assignment to solve this problem: Calculate the change in Enthalpy when 50cm3 if 0.2moldm-3 NaOH is added to 250cm3 of HCl. The initial temperature is 21.6C and it rose to 32.8C. I tried solving it by doing: Change in Enthalpy = ((250*4.18*11.2)/1000)/0.01 (0.01 from doing 0.05*0.2...
  2. 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...
  3. S


    i forgot the concepts understanding word by word without practical imaginative thinking. how to understand chemistry like a story. can anyone can tell me
  4. S

    Enthalpy & Hess's Law

    Hello everyone, I need quite urgent help. I have carried out experimentally two reactions as follows: 1. CaO + H2O -> Ca(OH)2 2. Ca(OH)2 + 2HNO3 -> Ca(NO3)2 + 2H2O to prove Hess's Law for this reaction: 3. CaO + 2HNO3 -> Ca(NO3)2 + H2O How do I do calculate the enthalpies? Is q=mcΔT enough...
  5. 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...
  6. JasonHerbalExt

    The enthalpy of formation, ∆Hf˚, equals zero at 25 °C for which of the following in t

    The enthalpy of formation, ∆Hf˚, equals zero at 25 °C for which of the following in t The enthalpy of formation, ∆Hf˚, equals zero at 25 °C for which of the following in their standard states? (A) elements (B) compounds (C) gases (D) solids
  7. S

    Enthalpy problem please help

    the enthalpy of solution of NAOH is -44.4 kj/mol when a sample of NAOH dissolves in 250 cm3 of water, the temperature of water changes by 14k. what is the mass of NAOH used in the experiment. answer is 13.9 g please show me the solution to get the answr. thanks
  8. 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...
  9. 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...
  10. K

    Molar enthalpy?

    I've learnt previously that Molar enthalpy is in terms of kJ per mole of the limiting reagent, but my school's chemistry notes said that it is in fact kJ per mole of the limiting reagent times the coefficient of the limiting reagent in the stoichiometric equation. so instead of just Q/n, it is...
  11. M

    The structure and reaction of benzene- enthalpy question

    1.) The average enthalpy of hydrogenation of a single c=c bond is -20J/mol. Predict the enthalpy change or complete hydrogenation of a benzene ring and write the name of the product formed. 2.) The actual enthalpy of hydrogenation of bezene is -250J/mol. using this information and your answer...
  12. I

    Does this reaction have a critical temperature?

    2 CCl4 (g) + O2 (g) --> 2COCl2(g) + 2Cl2(g) Predict the sign of ΔS, as the reaction proceeds to the right: the products have a higher ΔS because there are more mols of gaseous products than reactants. ΔG and ΔH are also positive at room temp. (it's not spontaneous). So does this reaction have...
  13. J

    farmation enthalpy and born-haber-cycle

    How can I calculate the enthalpy of formation for hematite(Fe2O3) with using of the born-haber-cycle? I have to select the values I need: lattice enthalpy=150*10^5 J/mol sublimation energy=4,18*10^5 J/mol hydration energy Fe3+=-43,3*10^5 J/mol hydration energy H+=-10,8*10^5 J/mol ionisation...
  14. D

    Help with enthalpy

    I am having trouble with question 6. My attempt: How do I do this? Nobody in my class understands and my teacher refuses to help. Please help.
  15. S

    Enthalpy of ionization?

    If the heat of neutralization of aqueous benzoic acid (a weak monoprotic acid) is -54.6 kJ/mol , what is the enthalpy of ionization of benzoic acid? I know that the formula for delta H = qrxn/ moles reacting I'm not sure how to find it. Any help appreciated!
  16. J

    Adiabatic Enthalpy Change

    I got a bit stuck on a practice question I was doing regarding enthalpy change: The temperature of one mole of gas was increased adiabatically from 273K to 548K (Cvm = 20.8J/k/mol). For the system calculate the change in enthalpy (∆H). So obviously ∆Q = 0 as it is adiabatic and therefore the...
  17. D

    Enthalpy reaction of NaHCO3 and HCL

    Could someone help me with the last part of calculating the enthalpy? This is what I have so far A 100 cm3 of 2 mol dm-3 hydrochloric acid was poured into a polystyrene cup. 14 grams of sodium bicarbonate was added with. Initial temperature was 21.0 C and final temperature was 12.0 C. The...
  18. S

    Enthalpy change of autoionization of water

    Why is the enthalpy change of the autoionization of water positive? Why does the pH of pure water increase with decreasing temp? Not sure.
  19. S

    Standard enthalpy question

    The choice highlighted and the fourth choice is wrong. I know the formula is 2CO+ O2===> 2CO2. Is choice 5 correct? I dont think so since they both have two as a coefficient that the answer would be choice 2 since the formula is products - reactants and itt would be CO2- CO not CO - CO2...
  20. L

    What is the enthalpy in kj/mol for the following?

    A reaction is peformed in which 50 ml of .400M silver nitrate and 75 ml of .100M hydrochloric acid are mixed together. The initial temperature of the solutionn was 25 C and the final temperature was 27.2 C. What is the enthalpy, in kj/mol, for the formation of the precipitate (silver chloride)...