| 单词 | reactant |
| 例句 | Once the temperature is sufficiently low, the concentration of the reactant gases on the catalyst surface increases and the reaction picks up speed again. Discovery made about Fischer Tropsch process could help improve fuel production 2023-10-05T04:00:00Z In some reactions, a single reactant substrate is broken down into multiple products. Concepts of Biology 2013-04-25T00:00:00Z The rate constant k is independent of the reactant concentrations, but it does vary with temperature. Chemistry 2019-02-14T00:00:00Z Enzymes do this by binding to the reactant molecules, and holding them in such a way as to make the chemical bond-breaking and bond-forming processes take place more readily. Biology for AP Courses 2022-06-09T00:00:00Z These reactions extract energy and produce the reactant that allows the cycle to start again. Miller & Levine Biology 2018-01-01T00:00:00Z That is, as the temperature of the reaction goes up due to its heat production, the reactant gases lose contact with the catalyst surface and their reaction slows down, which reduces the temperature. Discovery made about Fischer Tropsch process could help improve fuel production 2023-10-05T04:00:00Z Enzymes do this by binding to the reactant molecules and holding them in such a way as to make the chemical bond-breaking and -forming processes take place more easily. Concepts of Biology 2013-04-25T00:00:00Z This method involves measuring reaction rates for multiple experimental trials carried out using different initial reactant concentrations. Chemistry 2019-02-14T00:00:00Z For this reason, reactant molecules don’t last long in their transition state, but very quickly proceed to the next steps of the chemical reaction. Biology for AP Courses 2022-06-09T00:00:00Z Water is a lubricant and cushion, a heat sink, a component of liquid mixtures, a byproduct of dehydration synthesis reactions, and a reactant in hydrolysis reactions. Anatomy and Physiology 2013-06-19T00:00:00Z Finally, the site selectivity of the thianthrenation step is governed entirely by the electronic and structural properties of the reactant molecule. Molecular-decoration technique offers boost to medicinal chemists 2019-03-12T04:00:00Z The quicker-diffusing reactant — called the inhibitor — pushes back against the slower one, called the activator, effectively corralling the resulting product into a pattern of spots or stripes. Water filter inspired by Alan Turing passes first test 2018-05-02T04:00:00Z To illustrate the point with minimal complexity, only the simplest second-order reactions will be described here, namely, those whose rates depend on the concentration of just one reactant. Chemistry 2019-02-14T00:00:00Z The reactant and the product are the same in a circular pathway but different in a linear pathway. Biology for AP Courses 2022-06-09T00:00:00Z A substrate is a reactant in an enzymatic reaction. Anatomy and Physiology 2013-06-19T00:00:00Z Their internal bonds weaken after prolonged exposure to heat and collisions with reactant molecules, and their ligands start disintegrating. The new breed of cutting-edge catalysts 2016-09-05T04:00:00Z I: The order of a reaction refers to the influence of changes in reactant concentration on the rate of reaction. Tackle Chemistry on the MCAT With a Sample Question 2015-03-17T04:00:00Z This expression may be rearranged to express the concentration of the intermediate in terms of the reactant NO: Chemistry 2019-02-14T00:00:00Z ‘The amount of reactant present in the fiber is miniscule, and molecular transport and reaction processes are quite different,’ he says. New Molecular Sieve Offers Greener Way to Filter Chemicals 2014-07-09T04:00:00Z Synthesis reactions bond reactants together, a process that requires energy, whereas decomposition reactions break the bonds within a reactant and thereby release energy. Anatomy and Physiology 2013-06-19T00:00:00Z Treating graphene as a reactant rather than a product opens up other possibilities for novel and unexpected things. Perspective: A means to an end 2012-03-14T22:50:50.120Z And while methane is the standard reactant, any carbon source will do: Tour has even put cockroach legs on top of copper and produced a thin graphene film. Production: Beyond sticky tape 2012-03-14T22:50:43.050Z What will happen to the concentration of each reactant and product at equilibrium if more C is added? Chemistry 2019-02-14T00:00:00Z Finally, they devised an intermittent approach, allowing the membrane to grow under static conditions, then periodically replenishing the reactant supply. New Molecular Sieve Offers Greener Way to Filter Chemicals 2014-07-09T04:00:00Z For oxidative phosphorylation to occur, oxygen is used as a reactant and carbon dioxide is released as a waste product. Anatomy and Physiology 2013-06-19T00:00:00Z A Gaussian wave packet with the ground rovibrational state OH reactant was launched in the N + OH channel and propagated in time with the split-operator method. [Report] Revealing Atom-Radical Reactivity at Low Temperature Through the N + OH Reaction 2011-12-15T18:56:09.327Z In order to keep a reaction moving in the forward direction, we must supply reactant molecules and remove product molecules; in effect, we must provide a small driving force. The Fundamental Physical Limits of Computation 2011-06-01T17:45:02.143Z What will happen to the concentration of each reactant and product at equilibrium if H2O is removed? Chemistry 2019-02-14T00:00:00Z When they realized this setup wasn’t supplying enough reactant, they pumped the inner solution through the fiber, getting better coatings but struggling to control thickness and quality. New Molecular Sieve Offers Greener Way to Filter Chemicals 2014-07-09T04:00:00Z No matter what distance or reactant I assume, nothing we know will fit. Masters of Space Captain Strong took his place in the pilot's chair next to Tom and strapping himself in snapped out, "Feed reactant!" On the Trail of the Space Pirates Once, when a rocket scout crew was threatened with exploding reactant mass, he calmly told them to blast off into a desolate spot in space and blow up. Danger in Deep Space What will happen to the concentration of each reactant and product at equilibrium if CO is added? Chemistry 2019-02-14T00:00:00Z "If you so much as smell that grub, I'll come down and feed you into the reactant chamber!" Stand by for Mars! "Secure the Polaris, Tom, and tell Astro to get the reactant pile from the firing chamber ready for dumping when the hot-soup wagon gets here." The Revolt on Venus "Empty the reactant fuel tanks of all but enough for us to raise ship and touch down over to the fairgrounds," said Strong. On the Trail of the Space Pirates "And the reactant power of the Space Devil placed in the right spot would be the trigger to make it let go!" commented Roger. Danger in Deep Space What will happen to the concentration of each reactant and product at equilibrium if the temperature of the system is increased? Chemistry 2019-02-14T00:00:00Z Astro, how much could you get out of this baby by opening the by-pass between the cooling pumps and the reactant chamber? Stand by for Mars! The Solar Guard officer referred to the lead-lined jet sled that removed the reactant piles from all ships that were to be laid up for longer than three days. The Revolt on Venus On the power deck, the big cadet turned to his control panel, took a deep breath, and opened the reactant feeders wide. On the Trail of the Space Pirates On the morning of the fourth day he walked into the radar bridge where Roger and Alfie had been working steadily for seventy-two hours on an electronic fuse to trigger the reactant units. Danger in Deep Space What will happen to the concentration of each reactant and product at equilibrium if more Fe is added? Chemistry 2019-02-14T00:00:00Z "We could always open the reaction chamber and fill that," suggested Astro, indicating the hatch in the floor of the power deck that lead to the reactant chamber. Stand by for Mars! Knowing how to operate an atomic rocket motor was one thing, but understanding what went on inside the reactant pile was something else entirely. The Revolt on Venus "I don't know who's going to be first, but I can't even strip my ship by tomorrow morning, let alone soup up the reactant." Treachery in Outer Space We have to prepare reactant fuses and we have to build new reactor units. Danger in Deep Space What will happen to the concentration of each reactant and product at equilibrium if H2O is removed? Chemistry 2019-02-14T00:00:00Z "By the moons of Jupiter, we've run out of reactant fuel!" Stand by for Mars! And far below on the power deck, Astro began to feed the reactant energy into the firing chambers. The Space Pioneers "Then it must be the reactant," said Tom. Treachery in Outer Space Why, sir," he stammered, "it'd take—take—a ton of reactant fuel to pull something that size away from Tara. Danger in Deep Space What will happen to the concentration of each reactant and product at equilibrium if H2 is added? Chemistry 2019-02-14T00:00:00Z When we got rid of that hot tube back in space," explained Astro grimly, "we dumped the main reactant mass. Stand by for Mars! "One more lesson on the differential potential between chemical-burning rocket fuels and reactant energy and I'll blast off without a spaceship!" The Space Pioneers "From the sound of those rockets," said Astro, "Kit's feeders are clogged, or there's something in his reactant that the strainers are not filtering out." Treachery in Outer Space When they reached an altitude of a thousand miles above the surface of the planet, Loring maneuvered the jet boat into position outside the ship and placed the crude reactant bomb inside. Danger in Deep Space What will happen to the concentration of each reactant and product at equilibrium if the volume of the reaction vessel is decreased? Chemistry 2019-02-14T00:00:00Z The power deck has the rocket motors where the master panel should be and the panel is ready to go into what's left of the reactant chamber. Stand by for Mars! The bar charts in Figure 13.6 represent changes in reactant and product concentrations for three different reaction mixtures. Chemistry 2019-02-14T00:00:00Z "What kind of reactant is Quent Miles using in that ship of yours?" asked Walters sharply. Treachery in Outer Space Four hours later Loring and Mason came out of the reactant chamber carrying a small lead box. Danger in Deep Space What will happen to the concentration of each reactant and product at equilibrium if the temperature of the system is increased? Chemistry 2019-02-14T00:00:00Z Many systems, however, involve two or more coupled equilibrium reactions, those which have in common one or more reactant or product species. Chemistry 2019-02-14T00:00:00Z Many of the useful equilibrium calculations that will be demonstrated here require terms representing changes in reactant and product concentrations. Chemistry 2019-02-14T00:00:00Z "Back at the Academy, I failed to register a protest about someone dumping impure reactant into my feeders." Treachery in Outer Space "We're having a hard time getting the correct amount of reactant power we need in a unit this small." Danger in Deep Space Hydrogen ion cannot appear as a reactant because its concentration is essentially zero. Chemistry 2019-02-14T00:00:00Z Chemical equilibria are dynamic processes characterized by constant amounts of reactant and product species. Chemistry 2019-02-14T00:00:00Z This important reaction class is defined by changes in oxidation states for one or more reactant elements, and it includes a subset of reactions involving the transfer of electrons between reactant species. Chemistry 2019-02-14T00:00:00Z They cool the reactant fuel to keep it from getting too hot and wildcatting. Treachery in Outer Space Tom's worked out the ratios and the amount of reactant fuel needed in each unit for escape tangent. Danger in Deep Space Propane is an example of a hydrocarbon reactant: Chemistry 2019-02-14T00:00:00Z Negative values for electrode potentials are simply a consequence of assigning a value of 0 V to the SHE, indicating the reactant of the half-reaction is a weaker oxidant than aqueous hydrogen ions. Chemistry 2019-02-14T00:00:00Z A larger reduction potential means that it is easier to reduce the reactant. Chemistry 2019-02-14T00:00:00Z At a D-9 rate the reactant is hot enough to create power for normal flight. Treachery in Outer Space Likewise, the rate of a chemical reaction is a measure of how much reactant is consumed, or how much product is produced, by the reaction in a given amount of time. Chemistry 2019-02-14T00:00:00Z An equation is balanced when the same number of each element is represented on the reactant and product sides. Chemistry 2019-02-14T00:00:00Z The rate of reaction is the change in the amount of a reactant or product per unit time. Chemistry 2019-02-14T00:00:00Z Reaction rates are therefore determined by measuring the time dependence of some property that can be related to reactant or product amounts. Chemistry 2019-02-14T00:00:00Z If you return here with less than a quarter supply of reactant fuel, you will be disqualified. Treachery in Outer Space Compared with the reaction rate for large solid particles, the rate for smaller particles will be greater because the surface area in contact with the other reactant phase is greater. Chemistry 2019-02-14T00:00:00Z When a system has reached equilibrium, no further changes in the reactant and product concentrations occur; the forward and reverse reactions continue to proceed, but at equal rates. Chemistry 2019-02-14T00:00:00Z The reaction orders in a rate law describe the mathematical dependence of the rate on reactant concentrations. Chemistry 2019-02-14T00:00:00Z A later chapter section on reaction mechanisms will explain how a reactant’s concentration can have no effect on a reaction rate despite being involved in the reaction. Chemistry 2019-02-14T00:00:00Z The lead baffles around the reactant chambers had become loose and the reactant was spilling out, starting to wildcat. Treachery in Outer Space In each succeeding half-life, half of the remaining concentration of the reactant is consumed. Chemistry 2019-02-14T00:00:00Z Thus, hydrogen ion should not appear as a reactant or product in basic solution. Chemistry 2019-02-14T00:00:00Z The decomposition of hydrogen peroxide is a first-order reaction, and, as can be shown, the half-life of a first-order reaction is independent of the concentration of the reactant. Chemistry 2019-02-14T00:00:00Z How this energy compares to the kinetic energy provided by colliding reactant molecules is a primary factor affecting the rate of a chemical reaction. Chemistry 2019-02-14T00:00:00Z "Almost a full tank of reactant!" replied the young engineer. Treachery in Outer Space The frequency factor, A, reflects how well the reaction conditions favor properly oriented collisions between reactant molecules. Chemistry 2019-02-14T00:00:00Z It is helpful to view the process with regard to each individual reactant, that is, to represent the fate of each reactant in the form of an equation called a half-reaction: Chemistry 2019-02-14T00:00:00Z For example, a unimolecular reaction involves the reaction of a single reactant species to produce one or more molecules of product: Chemistry 2019-02-14T00:00:00Z By this convention, and the definitions of “reactant” and “product,” a chemical equation represents the reaction in question as proceeding from left to right. Chemistry 2019-02-14T00:00:00Z "But someone dumped impure reactant into my—" "What?" Treachery in Outer Space When the rates of the forward and reverse reactions are equal, the concentrations of the reactant and product species remain constant over time and the system is at equilibrium. Chemistry 2019-02-14T00:00:00Z What is the limiting reactant when 1.50 g of lithium and 1.50 g of nitrogen combine to form lithium nitride, a component of advanced batteries, according to the following unbalanced equation? Chemistry 2019-02-14T00:00:00Z The product concentration and the numerator of Qc decrease with time, the reactant concentrations and the denominator of Qc increase, and the reaction quotient consequently decreases until it becomes constant at equilibrium. Chemistry 2019-02-14T00:00:00Z A reaction exhibiting a large K will reach equilibrium when most of the reactant has been converted to product, whereas a small K indicates the reaction achieves equilibrium after very little reactant has been converted. Chemistry 2019-02-14T00:00:00Z If the system is stressed by adding reactant, either H2 or I2, the resulting increase in concentration causes the rate of the forward reaction to increase, exceeding that of the reverse reaction: Chemistry 2019-02-14T00:00:00Z The same logic can be used to explain the left shift that results from either removing reactant or adding product to an equilibrium system. Chemistry 2019-02-14T00:00:00Z Since the provided amount of KClO3 is less than the stoichiometric amount, it is the limiting reactant and may be used to compute the enthalpy change: Chemistry 2019-02-14T00:00:00Z Raising the temperature of the system is akin to increasing the amount of a reactant, and so the equilibrium will shift to the right. Chemistry 2019-02-14T00:00:00Z Because only the reactant is present initially Qc = 0 and the reaction will proceed to the right. Chemistry 2019-02-14T00:00:00Z A system at equilibrium is characterized by constant reactant and product concentrations, but the values of the reactant and product concentrations themselves need not be equal. Chemistry 2019-02-14T00:00:00Z If the reaction is endothermic the heat added can be thought of as a reactant. Chemistry 2019-02-14T00:00:00Z Next, we see that F2 is also needed as a reactant. Chemistry 2019-02-14T00:00:00Z The numbers of H atoms on the reactant and product sides of the equation are equal, but the numbers of O atoms are not. Chemistry 2019-02-14T00:00:00Z Each half-reaction will contain one reactant and one product with one element in common. Chemistry 2019-02-14T00:00:00Z An alternative approach to identifying the limiting reactant involves comparing the amount of product expected for the complete reaction of each reactant. Chemistry 2019-02-14T00:00:00Z Comparing these ratios shows that Si is provided in a less-than-stoichiometric amount, and so is the limiting reactant. Chemistry 2019-02-14T00:00:00Z Rate laws may exhibit fractional orders for some reactants, and negative reaction orders are sometimes observed when an increase in the concentration of one reactant causes a decrease in reaction rate. Chemistry 2019-02-14T00:00:00Z Redox reactions involve a change in oxidation number for one or more reactant elements. Chemistry 2019-02-14T00:00:00Z Coefficients from the equation are used to derive stoichiometric factors that subsequently may be used for computations relating reactant and product masses, molar amounts, and other quantitative properties. Chemistry 2019-02-14T00:00:00Z What is the limiting reactant in a reaction that produces sodium chloride from 8 g of sodium and 8 g of diatomic chlorine? Chemistry 2019-02-14T00:00:00Z These coefficients yield equal numbers of both H and O atoms on the reactant and product sides, and the balanced equation is, therefore: Chemistry 2019-02-14T00:00:00Z To remedy this, use the first step’s rate laws to derive an expression for the intermediate concentration in terms of the reactant concentrations. Chemistry 2019-02-14T00:00:00Z The N atom balance has been upset by this change; it is restored by changing the coefficient for the reactant N2 to 2. Chemistry 2019-02-14T00:00:00Z Some redox reactions involve the transfer of electrons between reactant species to yield ionic products, such as the reaction between sodium and chlorine to yield sodium chloride: Chemistry 2019-02-14T00:00:00Z An equation must represent equal numbers of electrons on the reactant and product sides, and so both atoms and charges must be balanced. Chemistry 2019-02-14T00:00:00Z This substance is the limiting reactant, and the other substance is the excess reactant. Chemistry 2019-02-14T00:00:00Z It interacts with a reactant to form an intermediate substance, which then decomposes or reacts with another reactant in one or more steps to regenerate the original catalyst and form product. Chemistry 2019-02-14T00:00:00Z Identifying the limiting and excess reactants for a given situation requires computing the molar amounts of each reactant provided and comparing them to the stoichiometric amounts represented in the balanced chemical equation. Chemistry 2019-02-14T00:00:00Z Hydrogen, therefore, is present in excess, and chlorine is the limiting reactant. Chemistry 2019-02-14T00:00:00Z Each reactant amount is used to separately calculate the amount of product that would be formed per the reaction’s stoichiometry. Chemistry 2019-02-14T00:00:00Z The reactant yielding the lesser amount of product is the limiting reactant. Chemistry 2019-02-14T00:00:00Z Notice that NO is a reactant in the first step of the mechanism and a product in the last step. Chemistry 2019-02-14T00:00:00Z This illustration shows a reaction in which hydrogen is present in excess and chlorine is the limiting reactant. Chemistry 2019-02-14T00:00:00Z Since silicon yields the lesser amount of product, it is the limiting reactant. Chemistry 2019-02-14T00:00:00Z This may seem counterintuitive, since the reaction rate certainly can’t be finite when the reactant concentration is zero. Chemistry 2019-02-14T00:00:00Z For a second-order reaction, is inversely proportional to the concentration of the reactant, and the half-life increases as the reaction proceeds because the concentration of reactant decreases. Chemistry 2019-02-14T00:00:00Z Tripling the concentration of a different reactant increases the rate of a reaction three times. Chemistry 2019-02-14T00:00:00Z When reactant species collide with both proper orientation and adequate energy, they combine to form an unstable species called an activated complex or a transition state. Chemistry 2019-02-14T00:00:00Z If temperature or reactant concentration is increased, the rate of a given reaction generally increases as well. Chemistry 2019-02-14T00:00:00Z The half-life of a reaction is the time required to decrease the amount of a given reactant by one-half. Chemistry 2019-02-14T00:00:00Z The half-life of a zero-order reaction decreases as the initial concentration of the reactant in the reaction decreases. Chemistry 2019-02-14T00:00:00Z Tripling the concentration of a reactant increases the rate of a reaction nine-fold. Chemistry 2019-02-14T00:00:00Z These reactant collisions must be of proper orientation and sufficient energy in order to result in product formation. Chemistry 2019-02-14T00:00:00Z Set the initial temperature and select the current amounts of each reactant. Chemistry 2019-02-14T00:00:00Z Doubling the concentration of a reactant increases the rate of a reaction four times. Chemistry 2019-02-14T00:00:00Z What is the order of the reaction with respect to that reactant? Chemistry 2019-02-14T00:00:00Z Increasing the concentration of a reactant by a factor of four increases the rate of a reaction four-fold. Chemistry 2019-02-14T00:00:00Z What is the order of the reaction with respect to that reactant? Chemistry 2019-02-14T00:00:00Z What are the orders with respect to each reactant? Chemistry 2019-02-14T00:00:00Z |
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