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| [[Image:Hess cycle.svg|thumb|A representation of Hess' law (where H represents enthalpy)]]
| | If you are distrustful of standard diets, you are happier with a healthy eating plan that we have created oneself. Lucky for you, these are really very easy to make with simply a little of research concerned.<br><br>Another method [http://safedietplansforwomen.com/bmr-calculator bmr calculator] is to avoid carb counting on individual foods altogether plus merely employ the carb counts found in low-carb diet booksand estimate the carb consumption by adding up all of the carbs, according to their counts, inside a day.<br><br>We could be man or female, nevertheless you nevertheless require muscle mass to raise the basal metabolic rate. This is a measure of how various calories your body burns every day. Already you understand which too many unused calories are bad for the wellness, so you want to begin to pay attention to how much muscle is on the body. It is worth it.<br><br>While supplementing with pyruvate, you needn't go on an overly stringent diet. But, should you eat anything you wish without regard to calories or fat consumption or without exercising, you'll only receive fatter. Your right bet is to follow a moderate, well-balanced however, low-fat diet and exercise plan that decreases your calories by no over 500 a day, either by exercise, a slight reduction in food, or perhaps a mixture of the 2. At www.ShopPharmacyCounter.com you sell best fat reduction supplements. Suppose you need an consumption of 2,200 calories a day to keep a weight. To lose fat, you need to cut 500 calories daily, for a caloric intake of 1,700 calories a day.<br><br>Then let's calculate the number of calories a have to help the daily escapades. Just multiply the calculated bmr by 1.2 should you don't exercise at all, 1.375 should you exercise lightly 1 to 3 occasions per week, 1.55 if you exercise moderately 3 to 5 occasions per week, 1.725 should you exercise hard 6 to 7 instances per week, or 1.9 if you have a physically demanding job and exercise each day or are training for a sports competition like a marathon.<br><br>At any given moment, 25 percent of all guys plus 33 percent of all ladies are on some kind of formal diet in the United States. More than 55 percent gain back all of their fat plus over what they started with.1 Unfortunately, most diets are a one-size-fits-all approach. With any diet book you pick off the bookstore shelf, or any older diets passed down by the terrific aunt, there are the same diet for everyone. Some of those are completely unsound nutritionally whilst others might be backed by superior nutrition principles. Yet, even those with wise nutrition principles don't personalize their approach to fit every person's body makeup. These are generally unluckily a one-size-fits-all dieting approach.<br><br>So you're suggesting which when a metabolic style workout I will eat whatever I need? Absolutely not! The kinds of foods we eat are as important as the sort of exercise you do. When you eat is just because significant because what we eat. In the next limited blogs I is discussing foods to consume and those to avoid, also the appropriate instances to consume for the many lucrative fat reduction. Be found on the lookout for the modern N-Motion Fitness recipe section on nmotionfitnessllc.com. |
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| '''Hess's Law of Constant Heat Summation''', also known as '''Hess's law''', is a relationship in [[physical chemistry]] named after [[Germain Henri Hess|Germain Hess]], a [[Swiss]]-born [[Russia]]n [[chemist]] and [[physician]] who published it in 1840. The law states that the total enthalpy change during the complete course of a reaction is the same whether the reaction is made in one step or in several steps.<ref name= "Aakash1">{{cite book|title=Chemistry for ISEET - Volume 1, Part A|year=2012|publisher=Varsity Education Management Limited|location=[[Hyderabad, India]]|author=Mannam Krishnamurthy|edition=2012|coauthors=Subba Rao Naidu|editor=Lokeswara Gupta|page=244|chapter=7}}</ref><ref>{{cite web|title=Hess's Law - Conservation of Energy|url=http://www.science.uwaterloo.ca/~cchieh/cact/c120/hess.html|publisher=University of Waterloo|accessdate=12 January 2014}}</ref>
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| Hess's law is now understood as an expression of the principle of conservation of energy, also expressed in the [[first law of thermodynamics]], and the fact that the [[enthalpy]] of a chemical process is independent of the path taken from the initial to the final state (i.e. enthalpy is a [[state function]]). It applies to the special case of paths consisting of chemical reactions (or changes of state) at constant temperature and pressure. Hess's law can be used to determine the overall energy required for a chemical reaction, when it can be divided into synthetic steps that are individually easier to characterize. This affords the compilation of standard [[enthalpy of formation|enthalpies of formation]], that may be used as a basis to design complex syntheses.
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| ==Definition ==
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| Hess's law states that the enthalpy or heat change accompanying a chemical reaction is independent of the pathway between the initial and final states.
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| In other words, if a chemical change takes place by several different routes, the overall enthalpy change is the same, regardless of the route by which the chemical change occurs (provided the initial and final condition are the same).
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| Hess's law allows the [[enthalpy]] change (ΔH) for a reaction to be calculated even when it cannot be measured directly. This is accomplished by performing basic algebraic operations based on the [[chemical equation]] of reactions using previously determined values for the enthalpies of formation.
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| Addition of chemical equations leads to a net or overall equation. If enthalpy change is known for each equation, the result will be the enthalpy change for the net equation. If the net enthalpy change is negative (ΔH<sub>net</sub> < 0), the reaction is exothermic and is more likely to be spontaneous; positive ΔH values correspond to [[endothermic]] reactions. [[Entropy]] also plays an important role in determining spontaneity, as some reactions with a positive enthalpy change are nevertheless spontaneous.
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| Hess's law states that enthalpy changes are additive. Thus the ΔH for a single reaction
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| : <math>\Delta H_{reaction}^\ominus = \sum \Delta H_{\mathrm f \,(products)}^{\ominus} - \sum \Delta H_{\mathrm f \,(reactants)}^{\ominus}</math>
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| where the <sup><s>o</s></sup> superscript indicates standard state values.
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| ==Examples==
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| 1) Given:
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| *B<sub>2</sub>O<sub>3</sub> (s) + 3H<sub>2</sub>O (g) → 3O<sub>2</sub> (g) + B<sub>2</sub>H<sub>6</sub> (g) (ΔH = 2035 kJ/mol)
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| *H<sub>2</sub>O (l) → H<sub>2</sub>O (g) (ΔH = 44 kJ/mol)
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| *H<sub>2</sub> (g) + (1/2)O<sub>2</sub> (g) → H<sub>2</sub>O (l) (ΔH = -286 kJ/mol)
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| *2B (s) + 3H<sub>2</sub> (g) → B<sub>2</sub>H<sub>6</sub> (g) (ΔH = 36 kJ/mol)
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| Find the ΔH<sub>f</sub> of:
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| *2B (s) + (3/2) O<sub>2</sub> (g) → B<sub>2</sub>O<sub>3</sub> (s)
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| After the multiplication and reversing of the equations (and their enthalpy changes), the result is:
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| *B<sub>2</sub>H<sub>6</sub> (g) + 3O<sub>2</sub> (g) → B<sub>2</sub>O<sub>3</sub> (s) + 3H<sub>2</sub>O (g) (ΔH = -2035 kJ/mol)
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| *3H<sub>2</sub>O (g) → 3H<sub>2</sub>O (l) (ΔH = -132 kJ/mol)
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| *3H<sub>2</sub>O (l) → 3H<sub>2</sub> (g) + (3/2) O<sub>2</sub> (g) (ΔH = 858 kJ/mol)
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| *2B (s) + 3H<sub>2</sub> (g) → B<sub>2</sub>H<sub>6</sub> (g) (ΔH = 36 kJ/mol)
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| Adding these equations and canceling out the common terms on both sides, we get
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| *2B (s) + (3/2) O<sub>2</sub> (g) → B<sub>2</sub>O<sub>3</sub> (s) (ΔH = -1273 kJ/mol)
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| 2) a) C<sub>graphite</sub>+O<sub>2</sub> → CO<sub>2</sub> (g) ;(ΔH = -393.5 kJ) (direct step)
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| :b) C<sub>graphite</sub>+1/2 O<sub>2</sub> → CO (g) ; (ΔH = -110.5 kJ)
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| :c) CO (g)+1/2 O<sub>2</sub> → CO<sub>2</sub> (g); (ΔH = - 283.02 kJ)
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| →In the reactions b) and c), the total ΔH = -393.5 kJ which is equal to ΔH in a)
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| The difference in the value of ΔH is 0.02 kJ which is due to measurement errors .
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| ==Extension to entropy and free energy==
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| The concepts of Hess's law can be expanded to include changes in [[entropy]] and in [[Gibbs free energy]], which are also [[state function]]s. The [[Bordwell thermodynamic cycle]] is an example of such an extension which takes advantage of easily measured [[Chemical equilibrium|equilibria]] and [[redox potential]]s to determine experimentally inaccessible [[Gibbs free energy]] values. Combining ΔG<sup><s>o</s></sup> values from Bordwell thermodynamic cycles and ΔH<sup><s>o</s></sup> values found with Hess's law can be helpful in determining entropy values which are not measured directly, and therefore must be calculated through alternative paths.
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| For the free energy:
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| :<math>\Delta G_{reaction}^\ominus = \sum \Delta G_{\mathrm f \,(products)}^{\ominus} - \sum \Delta G_{\mathrm f \,(reactants)}^{\ominus}.</math>
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| For [[entropy]], the situation is a little different. Because entropy can be measured as an absolute value, not relative to those of the elements in their reference states (as with ΔH<sup><s>o</s></sup> and ΔG<sup><s>o</s></sup>), there is no need to use the entropy of formation; one simply uses the absolute entropies for products and reactants:
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| :<math>\Delta S_{reaction}^\ominus = \sum S_{(products)}^{\ominus} - \sum S_{(reactants)}^{\ominus}.</math>
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| ==Applications==
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| Hess's law of constant heat summation is useful in the determination of enthalpies of the following:<ref name=Aakash1 />
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| #Heats of very slow reactions
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| #Heats of formation of unstable intermediates like CO<sub>(g)</sub> and NO<sub>(g)</sub>.
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| #Heat changes in phase transitions and [[allotropy|allotropic]] transitions.
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| #[[Lattice energy|Lattice energies]] of ionic substances by constructing [[Born-Haber cycle]]s if the [[electron affinity]] to form the anion is known, or
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| #Electron affinities using a Born-Haber cycle with a theoretical [[lattice energy]]
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| ==See also==
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| *[[Thermochemistry]]
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| *[[Thermodynamics]]
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| ==References==
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| {{reflist}}
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| {{refbegin}}
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| *{{cite book
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| | last = Chakrabarty
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| | first = D.K.
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| | title = An Introduction to Physical Chemistry
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| | publisher = Alpha Science
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| | year = 2001
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| | location = Mumbai
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| | pages = 34–37
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| | isbn = 1-84265-059-9}}
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| {{refend}}
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| ==Further reading==
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| *{{cite journal | doi = 10.1021/ed028p581 | author = Leicester, Henry M. | title = Germain Henri Hess and the Foundations of Thermochemistry | journal = The Journal of Chemical Education | year = 1951 | volume = 28 | issue = 11 | pages = 581–583 |bibcode = 1951JChEd..28..581L }}
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| ==External links==
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| *[http://www.chemteam.info/Chem-History/Hess-1840.html Hess' paper (1840) on which his law is based] (at ChemTeam site)
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| *[http://www.adamequipment.com/education/Documents/experiment_6.pdf a Hess’ Law experiment]
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| [[Category:Chemical thermodynamics]]
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| [[Category:Physical chemistry]]
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| [[Category:Thermochemistry]]
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If you are distrustful of standard diets, you are happier with a healthy eating plan that we have created oneself. Lucky for you, these are really very easy to make with simply a little of research concerned.
Another method bmr calculator is to avoid carb counting on individual foods altogether plus merely employ the carb counts found in low-carb diet booksand estimate the carb consumption by adding up all of the carbs, according to their counts, inside a day.
We could be man or female, nevertheless you nevertheless require muscle mass to raise the basal metabolic rate. This is a measure of how various calories your body burns every day. Already you understand which too many unused calories are bad for the wellness, so you want to begin to pay attention to how much muscle is on the body. It is worth it.
While supplementing with pyruvate, you needn't go on an overly stringent diet. But, should you eat anything you wish without regard to calories or fat consumption or without exercising, you'll only receive fatter. Your right bet is to follow a moderate, well-balanced however, low-fat diet and exercise plan that decreases your calories by no over 500 a day, either by exercise, a slight reduction in food, or perhaps a mixture of the 2. At www.ShopPharmacyCounter.com you sell best fat reduction supplements. Suppose you need an consumption of 2,200 calories a day to keep a weight. To lose fat, you need to cut 500 calories daily, for a caloric intake of 1,700 calories a day.
Then let's calculate the number of calories a have to help the daily escapades. Just multiply the calculated bmr by 1.2 should you don't exercise at all, 1.375 should you exercise lightly 1 to 3 occasions per week, 1.55 if you exercise moderately 3 to 5 occasions per week, 1.725 should you exercise hard 6 to 7 instances per week, or 1.9 if you have a physically demanding job and exercise each day or are training for a sports competition like a marathon.
At any given moment, 25 percent of all guys plus 33 percent of all ladies are on some kind of formal diet in the United States. More than 55 percent gain back all of their fat plus over what they started with.1 Unfortunately, most diets are a one-size-fits-all approach. With any diet book you pick off the bookstore shelf, or any older diets passed down by the terrific aunt, there are the same diet for everyone. Some of those are completely unsound nutritionally whilst others might be backed by superior nutrition principles. Yet, even those with wise nutrition principles don't personalize their approach to fit every person's body makeup. These are generally unluckily a one-size-fits-all dieting approach.
So you're suggesting which when a metabolic style workout I will eat whatever I need? Absolutely not! The kinds of foods we eat are as important as the sort of exercise you do. When you eat is just because significant because what we eat. In the next limited blogs I is discussing foods to consume and those to avoid, also the appropriate instances to consume for the many lucrative fat reduction. Be found on the lookout for the modern N-Motion Fitness recipe section on nmotionfitnessllc.com.