Chemistry, 18.02.2020 05:33 donuteatingcat

The 1995 Nobel Prize in chemistry was shared by Paul Crutzen, F. Sherwood Rowland, and Mario Molina for their work concerning the formation and decomposition of ozone in the stratosphere. Rowland and Molina hypothesized that chlorofluorocarbons (CFCs) in the stratosphere break down upon exposure to UV radiation, producing chlorine atoms. Chlorine was previously identified as a catalyst in the breakdown of ozone into oxygen gas. Using the enthalpy of reaction for two reactions with ozone, determine the enthalpy of reaction for the reaction of chlorine with ozone.1) ClO(g) +O₃(g) > Cl(g) +2O₂(g); Hrxn = -122.8 kJ/mol
2) 2O₃(g) ---> 3O₂(g); Hrxn = -285.3 kJ/mol
3) O₃(g) + Cl(g) > ClO(g) + O₂(g); Hrxn =

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Answer from: dbenjamintheflash5

The $\Delta H^o_{rxn}$ for the reaction is -162.5 kJ/mol

Explanation:

Hess’s law of constant heat summation states that the amount of heat absorbed or evolved in a given chemical equation remains the same whether the process occurs in one step or several steps.

According to this law, the chemical equation is treated as ordinary algebraic expressions and can be added or subtracted to yield the required equation. This means that the enthalpy change of the overall reaction is equal to the sum of the enthalpy changes of the intermediate reactions.

The given chemical reaction follows:

$O_3(g)+Cl(g)\rightarrow ClO(g)+O_2$ $\Delta H^o_{rxn}=?$

The intermediate balanced chemical reaction are:

(1) $ClO(g)+O_3(g)\rightarrow Cl(g)+2O_2(g)$ $\Delta H_1=-122.8kJ/mol$

(2) $2O_3(g)\rightarrow 3O_2(g)$ $\Delta H_2=-285.3kJ/mol$

The expression for enthalpy of the reaction follows:

$\Delta H^o_{rxn}=[1\times (-\Delta H_1)]+[1\times \Delta H_2]$

Putting values in above equation, we get:

$\Delta H^o_{rxn}=[(1\times (-(-122.8))+(1\times (-285.3))=-162.5kJ/mol$

Hence, the $\Delta H^o_{rxn}$ for the reaction is -162.5 kJ/mol

Answer from: Quest

The answer to your question really depends on three things: how much water you have, how cold it is to start out, and how cold the things around it are. water actually freezes when it gets to 32 degrees fahrenheit (0 degrees celsius), but the time it takes to get there may be different. let's start with the first. if you take two glasses, and fill one with a tiny bit of water, and the other about halfway, then put them both in the freezer, the one with less water will freeze first (you can try this at home, but i recommend using plastic cups and not glass ones). now let's move on to the second part. let's say you have two glasses, and you fill one with really cold water that has been in the refrigerator, and the other with really hot water from the sink. if you put both of them in the freezer, the one that started out colder will freeze first. for the third part, let's imagine that you have two glasses with the same amount of water in them, and the water is at the same temperature. imagine putting one outside on a really really cold day in georgia, and having a friend in alaska put one outside on the same day. since it would be so much colder in alaska, the glass of water there would freeze before yours. so, if you took a tiny bit of really cold water in a glass, and put it outside on a cold day in alaska, it would freeze a lot faster than a big glass of hot water outside on a cold day in georgia.

Answer from: Quest

Ais stronge