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Catalysts and Catalysis
Catalysts are compounds or elements which take part in a reaction without getting used up themselves.
950 Questions
How does a catalyst usually emerge from a reaction?
A catalyst typically emerges unchanged from a reaction, as it speeds up the reaction without being consumed itself. It provides an alternative pathway for the reaction to occur with lower activation energy, making the reaction proceed faster.
What if your body relies on biological catalysts called what to control cell processes?
Your body relies on biological catalysts known as enzymes to control cell processes. Enzymes facilitate chemical reactions in cells by speeding up the rate of these reactions without being consumed in the process. They play a critical role in maintaining cellular functions and overall health.
Equilibrium position. The catalyst speeds up the rate at which equilibrium is reached by lowering the activation energy for both the forward and reverse reactions equally. The concentrations of reactants and products at equilibrium remain the same.
How many moles of precatalyst are used in this reaction?
The number of moles can be calculated by dividing the given mass of the precatalyst by its molar mass. Just use the formula: Number of moles = Mass of precatalyst (g) / Molar mass of precatalyst (g/mol).
A catalyst lowers the activation energy of a reaction, making it easier for the reactants to form products. It does not change the potential energy of the reactants or products, nor does it affect the overall heat of the reaction.
If a catalyst is added to a system at equilibrium and the temperature and pressure remain constant?
The catalyst will accelerate the forward and reverse reactions equally, therefore not changing the position of the equilibrium. This results in the system reaching a new equilibrium faster but with the same concentrations of reactants and products as before the catalyst was added.
What type of catalyst lowers the energy of activation for a reaction?
A catalyst lowers the energy of activation for a reaction by providing an alternative reaction pathway with lower activation energy. This allows the reactants to more easily overcome the energy barrier and proceed to form products at a faster rate.
Enzymes that act as catalysts for chemical reactions can also be performed by RNA molecules called ribozymes. Ribozymes, like enzymes, can speed up chemical reactions and are capable of catalyzing a wide range of biochemical reactions in living cells.
Which catalyst is used in any esterification?
An acid catalyst is used can be in many forms such as sulfuric acid or ion-exchange resin.
What are Molecules that act as catalysts in biological systems?
Enzymes are molecules that act as catalysts in biological systems by speeding up chemical reactions without being consumed in the process. They are essential for various cellular functions such as metabolism, signaling, and DNA replication. Enzymes have specific shapes that allow them to interact with specific substrates and facilitate their conversion into products.
A. Thermals
A Conductor is a material which allows either heat or electricity to pass easily through it.
A Catalyst is a material which speeds up a chemical reaction without being used up itself.
An Enzyme is a biological catalyst, i.e. a catalyst which occurs in living things.
Chemical Bond refers to the forces which hold atoms together in a molecule or material.
B. Conductors. Conductors are materials that readily transfer thermal energy due to their ability to easily allow the flow of heat through them. Thermals, enzymes, catalysts, and chemical bonds are not typically associated with the transfer of thermal energy.
What compound is more acidic Mn2O7 or MnO2?
Mn2O7 is more acidic than MnO2. This is because Mn2O7 is a peroxide compound that contains more oxygen atoms and can release more H+ ions when dissolved in water, making it a stronger acid than MnO2.
Temperature is the most important factor affecting the reaction rate in this scenario. By increasing the temperature with the lighted match, the kinetic energy of the particles is increased, leading to more collisions and a faster reaction between the match and the candle wick.
A catalyst is added to the fiberglass resin to do what?
A catalyst is added to fiberglass resin to initiate the chemical reaction that causes the resin to harden or cure. This process is known as polymerization, and the catalyst helps speed up the curing time of the resin, allowing it to form a strong and durable composite material.
Enzymes are not typically considered food additives on their own, but they are used in food processing as processing aids to help improve or speed up certain reactions, such as breaking down components like proteins, fats, or carbohydrates. Enzymes are naturally occurring and can sometimes be derived from animal, plant, or microbial sources.
Enzymes are special proteins that act as biological catalysts, speeding up chemical reactions in living organisms. They work by lowering the energy needed for a reaction to occur, allowing processes like digestion and metabolism to happen more efficiently. Each enzyme is specific to a particular reaction, like a key that fits into a specific lock.
Determination of the percentage of MnO2 IN pyrolusite?
Determination of MnO2 in pyrolusite
Author name: Xiaoxiao Zeng
Learner Code: B876496
Abstract: In this paper, employing a back titration of KMnO4 method to determine the content of MnO2 in pyrolusite. The %w/w MnO2 in the sample is 29.41%.
Keywords: pyrolusite; manganese dioxide; titration；sample；determination；accuracy；precision；confidence interval.
1 Introduction
The important component of pyrolusite is manganese dioxide[1]. A sample of pyrolusite was taken from a mine at Heshang area in Guangxi province, which is a very low-grade ore. In order to utilize the low-grade pyrolusite, we must find a good method to solve the problem.
The main component of pyrolusite is manganese dioxide. Is a kind of common manganese mineral. Pyrolusite is very soft, and it softer than people fingernails. The pyrolusite color is gray-black with a metallic luster. Some pyrolusite like arborization on rock surface, it's very amusing. So it is called pseudofossils.
A new hydrometallurgical method has to be developed to produce a chemical material of manganese sulfate. Thus the approximate content of MnO2 in the pyrolusite must be determined. The content of MnO2 in the pyrolusite can be measured using one of the methods of iodimetry[1]，oxalatometry[2]，hydrogen peroxidometry[3]and ferrometry[4]，that all meet the accuracy and precision for the test of MnO2 in the pyrolusite, in theory. Oxalatometry is selected to determine manganese dioxide in the pyrolusite, basing on a standard solution of KMnO4 is stable and convenient to prepare and stock, despite of ferric ion interfering the analyses. The accuracy (relative error) and precision (standard deviation) should be ±5% and ±0.2% in this experiment, respectively.
2 Principle of experiment
Manganese dioxide is a main component in pyrolusite. As a result of manganese dioxide is a strong oxidizer. Obviously, KMnO4 cannot used directly titration method.In the absence of oxidizer conditions, manganese dioxide is hardly dissolved in acid or base. Therefore, we cannot use directly with reducing agents for titration, we adopt the back titrimetry.Under acidic conditions, an excessive sodium oxalate and a 50-mL 3.7 mol/l H2SO4 solution were added in the pyrolusite, the manganese (IV) was reduced to Mn2+ ion dissolved in water. The remaining Na2C2O4 was titrated with a standard solution KMnO4 involved in the chemical equations as follows.
MnO2+C2O42-+4H+=Mn2++2CO2↑+2H2O
2MnO4-+5C2O42-+16H+=2Mn2++10CO2↑+8H2O
According to the stoichiometric relation of Na2C2O4 to KMnO4 and the consumed volume of the titrant, we can calculate the content of manganese dioxide in the sample of pyrolusite.
3 Reagents and apparatus
Reagents:The standard solution of 0.0208-mol·L-1 KMnO4, which is diluted with a 0.2080-mol/L stock solution of KMnO4; The analytical reagent of Na2C2O4 (AR); The solution of 3-mol·L-1H2SO4; H2SO4 (AR).
Apparatus: Some Beakers; Medicine spoon; Glass rod; An electronic analytical balance; Watch glass; Water-bath boiler; Electric cooker;Thermometer; A 25.00-mL volumetric pipette; A 250-mL Volumetric flask.
In order to get an accurate value, we must calibrate a 25-mL volumetric pipette and an electronic analytical balance.
Calibrate the equipments.
a. volumetric pipette
Weighed a dry volumetric flask (25 mL) with a stopper. Filled pipette with distilled water and delivered the water into the flask, stoppered container to avoid evaporation loss. Recorded the room temperature is 29oC and reweighed the container to obtain the weight in air of the water delivered by the pipette. Used the density of water in air (d = 0.9959 g/mL at 29oC) to calculate the volume of the pipette. According to the mass of water delivered by the pipette is 25.0196 g, the volume of the pipette is 25.1226 mL. The tolerance is 0.12 mL, that is larger than 0.06 mL, thus the pipette is production of class C.[5]
b. electronic analytical balance
Leveled the balance using the air-bubble float and leaved the balance constantly under power. When a calibration button was pushed, a 200.0000-g test weight was desired to load on the pan, the balance calibrated itself to full accuracy and returned to weighing mode within seconds.
4 Experimental
4.1 Sampling of pyrolusite
Pulverizing：Took a 1.5-kg pyrolusite from a barrel using the sampling methodology of compact solid [6] and pulverized the pyrolusite by ceramic mortar. After Blending equably, an approximately 10-g pyrolusite powder was coned and then to be flatten. A sample pyrolusite was sampled by quartering [8].
4.2 Scaling of sample of pyrolusite and standard reagents preparing standard solution.
Calibrated electronic balance and scaled samples and standard reagents; prepared standard solution.
In order to guarantee result accuracy, we must calibrate electronic before we use it.
Scaled 2.2788 grams pyrolusite sample and put it into a 250-mL beaker.
According the probable content of MnO2 scaled a 2.2059-g Na2C2O4 reagent and put it into the beaker. Then added a 50-mL 3mol·L H2SO4 solution and a 2-ml thick H2SO4 solution into the beaker.
Cover a watch glass on the beaker. Dissolving in 70~80℃ the water bath, until no longer emitted CO2 bubble. Also there had no black pellets in the residue. Generally, not surpassed 30 minutes when dissolved, in order to avoid or reduce loss of the oxalic acid. Wash the beaker's wall and the watch glass several times.
4.3 Pretreatment of pyrolusite
There were a lot of solid impurities, so we must remove it out. We used long neck funnel and filter paper to remove the solid materials from solution by filtration. We must perform trial separations of filtration. The experimental results show that MnO2 in the sample of pyrolusite had been transferred into the analyte solution (250 mL), completely.
4.4 Titration
Took the titration of a titrant VS a measured volume solution of sodium oxalate; recorded the data of volume of the consumed titrant. (Repeat 4~5 times); processed the experimental data and uated the results.
Heated conical flask in 70~80℃ the water bath, and used the KMnO4 standard solution to titrate until the solution became micro-red. No depigment for a half minute indicated the end-point had reached.
The reaction vate of MnO2 with Na2C2O4 is slow under room temperature. So we must heat up the solution. But the temperature cann't be too high. If the temperature exceeded 90℃, the H2C2O4 should be vaporized.
Transferred a 25.00-mL aliquot of the analyte solution from the 250-mL volumetric flask. Titrated the analyte solution with a 0.0208-mol/L KMnO4 titrant and required 16.73 mL to reach the end point. Similarly, repeated the titration four times and recorded the desired the volumes of the titrant, processed the data using statistical method (t Test) [7] and listed the result in Table 1. The result shows that there are not data of the volumes falling outside the confidence interval [16.73, 16.97].
Table 1 data of process for the titrant volumes
Times Iterms
1
2
3
4
5
Vs(mL)
16.73
16.97
16.81
16.80
16.88
s(mL)
16.83
s
0.09138
t0.95,4
2.776
Confidence limit
(x±t s/√n)
（16.83±0.11）
Confidence interval
[16.73,16.97]
There are two stoichiometric reactions involved in the oxalatometric titration
MnO2+C2O42-+4H+=Mn2++2CO2+2H2O 2.1
2MnO4-+5C2O42-+16H+=2Mn2++10CO2+8H2O 2.2
Due to the ratio of the moles MnO4- to the moles C2O42- is that
moles MnO4-∶moles C2O42-=2∶5.
Thus
moles C2O42-=5 moles MnO4-/2
Substituting for moles of MnO4- leaves us with an equation that is solved for the consumed moles of Na2C2O4.
Consumed moles of Na2C2O4=5×cs×Vs/2
Consumed moles of Na2C2O4=5×0.0208×16.73×10-3/2=8.7×10-4 (moles)
According to the ratio of the moles MnO2 to the moles C2O42- is that
moles MnO2∶moles C2O42-=1∶1.
So
Moles of MnO2=total moles of Na2C2O4-consumed moles of Na2C2O4×10
=total moles of Na2C2O4-consumed moles of Na2C2O4×10
=2.2059/134-8.7×10-4×10
=1.646×10-2 - 8.7×10-3
=7.76×10-3(moles)
Finally, the %w/w MnO2 in the sample is
-×100= -×100
=7.76×10-3×86.94×100/2.2788
=29.61
Similarly, calculate the %w/w MnO2 in the sample for replicated titrations are 29.15, 29.46, 29.46 and 29.31, respectively.
5 Discussion and Result
5.1 Process the data of analyses and result presentation.
Calculate the mean and the standard deviation of the set of data 29.61%, 29.15%, 29.46%, 29.46% and 29.31% are 29.41%and 0.18%. Check Table 13 in reference book [7] to obtain the t0.95 (4 degrees of freedom) of the statistic is 2.776. And now the confidence limit of the %w/w MnO2 in the sample becomes [29.14±0.15], that means that the mean of the population falls into the confidence interval 95% probability level.
5.2 Error analysis
The main errors in this determination root in the volatilization of oxalic acid and the interference of ferric ion, and that the statistical weight of the latter error is bigger than the former's. When the %w/w iron in the sample ore is 4.4, the error will be 4.7 [4]. The accuracy (relative error) is probably ±5% and the precision (standard deviation) should be ±0.2% in this experiment, but the results could meet the desire for classifying the grade of a pyrolusite. More accuracy and precision could meet ±0.5% and ±0.2% in next assignment where the analyte, which is reserved from this determination, will be measured by employing Atomic Absorption Spectrometry (AAS).
Why silica gel acts as catalyst?
Because of the following reasons :
1- The big surface area of the silica gel (up to 800 square meter for one gram) .
2- Silica gel ability to adsorb many other substances & compound which them self may acts as catalyst .
3 - The high thermal ,chemical & deformation resistance of silica gel .
4-The existance of the active OH groups which can directly make bond to other chemical particles ,or displaced by other chemical groups or the positive H ion displaced with other active ions .
5- Silica gel undergoes reverse reactions simply .
What are the uses of catalysts in everyday life?
Catalysts are used in everyday life to speed up chemical reactions in processes such as catalytic converters in cars to reduce emissions, in industrial chemical production to increase efficiency, in food production to enhance flavor and texture, and in the pharmaceutical industry to synthesize drugs.
How a catalyst effects chemical reaction?
Catalysts allow chemical changes to occur much more rapidly. Reactions that usually take years can happen before your eyes in seconds.
From my understanding there is no 100% agreed upon reason for how they do this. There are a number of widely regarded theories though.
The key enzyme involved in carbon fixation is called?
The key enzyme involved in carbon fixation is called ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). It catalyzes the first step in the process of carbon fixation during photosynthesis, where carbon dioxide is converted into organic molecules.
The catalyst for the market revolution was a series of innovations in?
The catalyst for the market revolution was a series of innovations in transportation and communication, such as the steam engine, canals, roads, and the telegraph. These advances allowed for goods and information to move more quickly and efficiently across the country, leading to increased industrialization and economic growth.
