Gravimetric Analysis of a Chloride Salt

Gravimetric Analysis of a Chloride Salt Rania Williams Nour Wehbe Purpose To discover the amount of chloride in a strange salt, in order to demonstrate regular methods used in gravimetric analysis Theory This equation describes the reaction between silver ion and chloride which results in the product silver chloride. Ag+ (aq) + Cl (aq) → AgCl (s) Silver nitrate is used to precipitate chloride because it gives the best results. AgCl Solubility in water: Silver chloride’s solubility is very low; however the salt is still soluble to some degree. If precipitate is not complete, the results will be very low. Ksp = 1.6 x 10-10 Precipitation occurs in acid to greatly reduce any interference from acid ions. These ions form co-precipitates with silver in acid containing no charged ions. Due to co-precipitates the results would be higher. Also in order for precipitation to occur in acid there needs to be some excess of silver ion at the end of the reaction to reduce the chances of silver chloride becoming more soluble. Co-precipitation would result in higher results. Description: The precipitate is heated in order to coagulate it. When it coagulates it will become a clumpy colloidal like form. In this form it will become more difficult for the precipitate to penetrate the filter paper. If the coagulate did go through, the results would be lower. If nitric acid had not been added to the precipitate it would become more vulnerable in penetrating the filter paper. If this had happened the experiment would have to be done again as there would be no way to determine the percentage of chloride in the salt. Photodecomposition: The equation for photodecomposition occurring in the air: AgCl (s) → Ag (s) + Â ½Cl2(g) When the silver chloride has dried and put into light it will decompose into chlorine and silver. If photodecomposition occurs in air, the results would be low, however if this decomposition occurred with excess silver ion in an aqueous solution there will be another reaction (3Cl2(g) + 9H2O (l) + 5Ag+ (aq) → 5AgCl (s) + ClO3(aq) + 6H3O+ (l)), which will make the results high. How much precipitate is lost by washing with 100ml fresh water? Ksp = [Ag][Cl] x x = x2 1.6 x 10-10 = 1.3 x 10-5 1.3 x 10-5= C/0.10 L C =1.3 x 10-5x 143 mol/0.10 L C = 0.01859 mol/L (0.01859)(0.10) = 0.001859 = 1.810-3 g The precipitate is lost due to the solubility of it. The solubility of the precipitate is very low so not much would be lost, however this still would make the results lower. Ions that may co-precipitate with chloride ion: When precipitation occurs quickly the chances of co-precipitation occurring greatly increases. Anions from some acids may co-precipitate with the chloride ion, forming co precipitates. These co precipitates will alter the results, making them CO32-, OH and NO3 Procedure The code number of the unknown salt that was placed on the station was recorded. This sample was kept for the full duration of the experiment. Using the analytical balance, 0.1175g of the sample was weighed out by difference and placed in a 250ml beaker. The beaker was labeled to avoid confusion between partners. The approximate volume of 0.1 M silver nitrate was calculated using the sample’s mass, 0.1175g. The mass of the sample was multiplied by the percentage concentration of the chloride then divided by 35.5. The result was then divided by 0.1. The result was converted into ml. 5 ml of excess was then added to the result, making the final result and approximate volume of silver nitrate added, 23ml. In the 250ml beaker with the sample, 100ml of distilled water and 1ml of 6M nitric acid was added to the beaker. 23ml of 0.1M silver nitrate was measured out in a 25ml graduated cylinder then slowly poured into the 250ml beaker. The solution was placed on a hot plate then gently stirred. The solution was stirred until it became close to boiling. In order to test for completeness the solution had a couple drops of silver nitrate poured into it to test that the entire chloride ion had been precipitated. The solution showed that it was complete. The 250ml beaker with the solution was then placed into the assigned drawer, to limit its light exposure. Using a piece of soft tissue paper the crucible which had already cooled was weighed, it had a mass of 30.6707. The vacuum filtration arrangement was set up. The solution without the precipitate was slowly poured into the filter. 5ml of 0.1M nitric acid was used for washing the precipitate. After a couple washings the precipitate was also placed into the filter. A wash bottle was used to help any remaining precipitate out of the beaker. The precipitate was again washed with 0.1M nitric acid. The crucible was then removed from the vacuum filtration arrangement. The leftover washings were disposed of. The crucible was washed once again in the vacuum filtration arrangement. The washing (mainly nitric acid) was taken to the T.A. for testing if the precipitation is complete by doing a washing with hydrogen chloride on the nitric acid. The first test showed completeness. The crucible was again latched onto the vacuum filtration arrangement to be washed with 3ml of acetone. The acetone was handed to the T.A. for disposal. The crucible was given to the T.A. to put in the oven for drying of the precipitate. The oven had a starting temperature of 110 Â °C and after 30 minutes had a temperature of 119 Â °C. The crucible was then cooled in the desiccator for 10 minutes then weighed with an analytical balance. The result was recorded. Observations Data tables Sample masses Crucible masses Approximate volume of the liquids and solutions used to was the sample Temperature of Oven Crucible drying and cooling times: Calculations Amount of AgNO3 required (calculated amount + 5mL) (0.1175)(0.55)/35.5/0.1 0.018204225 * 1000mL/1L = 18.204225 18.204225 + 5 = 23.20422525mL 23mL of AgNo3 needed Percentage chloride in sample Uncertainties Relative error Relative spread of the percentage of chloride found 62.06% 56.92% / 59.49% = 0.086401076 * 10 = 0.86401076 ppt = 0.8640 ppt Discussion My results were higher due to the photodecomposition of the precipitate that most likely occurred due to an excess of silver ion in the solution. This was a result of human error, as I waited for the precipitate to cool down I did not leave it out of light and failed to ensure that there was not an excess of silver ion in my solution. My results could also be higher due to any co-precipitates from anions such as these: CO32-, OH and NO3 . The results could have also become higher due to not being washed properly. When washing the precipitate only with 3ml of acetone and 5ml of water this may have been possible. When compared with the actual result, my result was higher. My partner’s results were lower than the real value due to some of her sample being lost during filtration. Sample being lost during filtration is almost unavoidable. Even though she may not have lost a lot of her sample, her initial salt mass was just 1.002g. Losing sample from a sample that was already so small contributed to her results being lower than the actual value. She also may have not allowed for complete precipitation of the chloride ion, resulting in lower results. During the heating of her solution her precipitate coagulated but there were stills some parts of the precipitate that were very tiny were susceptible of being loss the vacuum filtration. When compared with the actual result, my partner’s result was lower. The average of my partner and I’s results were very close to the actual result, though the average of our results was still higher than the actual result. Conclusion The sample number for the unknown salt is 343. The average percentage of the chloride from two trials is 59.49%, whilst the actual percentage of chloride is 58.81%. The uncertainty for the percentage of chloride for my results was 0.2041 and 0.2430 for my partner. The precision of my results was 5.526%, whilst my partner’s was 3.214%. The accuracy of the results was 0.8640 ppt. References Books: R.C.Burk, M.Azad, X.Sun, P.A. Wolff, Introductory Chemistry Laboratory Manual, Carleton University, Ottawa, 2014-15. Websites: Bishop, Mark. Bases. Bases. CHIRAL PUBLISHING COMPANY. 2013. Web. http://preparatorychemistry.com/Bishop_Base_Identification.htm>.

Home Recipe for Food Tech/Cooking Students †Fresh and Fried Spring Rolls Essay

Ingredients – makes 16 large spring rolls: 1 cup thinly sliced carrot 1 cup shredded Chinese cabbage 1 cup spring onions thinly sliced 1 cup mushrooms diced 1 1/2 cups thin rice noodles 16 sheets of defrosted spring roll pastry ( for fried spring rolls) 16 sheets of rice paper (for fresh spring rolls) 450g chicken mince (if making fried spring rolls) Method: Fried Spring Rolls: 1.Boil enough water to submerge the noodles and place both the water and noodles in a bowl to break them up and soften them. Let them soak for about 2-3 minutes. Remove with a colander. 2. Chop up all vegetables finely and mix together a long with the chicken and noodles in a large bowl. 3.Line up the spring roll pastry diagonally to you and put the mixture of veggies on the corner closest to you. 4.Roll the pastry up until you reach halfway. Fold in the corners and continue to roll. 5.Once you roll it until you have a little flap of pastry sticking out, wet it with a few drops of water to seal it to the rest of the roll. 6.Cook the spring rolls in the vegetable oil for 2-3 minutes until golden brown and crunchy. 7.Remove from oil and drain excess off via paper towel. 8.Serve the fried spring rolls with sweet chilli sauce for dipping. Fresh Vegetable Spring Rolls: 1.Place the noodles in warm water to soften them like you did with the noodles in step 1 of the fried spring rolls. Remove with a colander. 2.Place the rice paper in warm water after removing the noodles. 3.Follow steps 2-5 of the fried spring rolls recipe with the exception on using no chicken and substituting the pastry for the softened rice paper. 4.Serve with soy sauce.

Henrik Ibsen’s play A Doll’s House Essay

Henrik Ibsen’s play A Doll’s House is about â€Å"domestic politics† (Hurwitt, 2004, p. D-2).   Ibsen created a seemingly perfect atmosphere, enough to make one believe that marital bliss exists in such a setting.   As Hurwitt (2004) narrates, â€Å"the whole household contributes to the impression of marital bliss† (p. D-2). However, as the play progressed, it slowly becomes obvious that Ibsen wanted to show more than the problems of a married couple.   He evidently wanted to paint a socially significant picture.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   The play’s story is domestic in scope, primarily because two of the main characters are husband and wife.   Nonetheless, the play did include broader issues.   It showed how society in the 1800s view marriage, the functions assigned to man and wife, and the limitations it gave to women in general.   It is also climactic in structure. The three main characters are Nora and Torvald Helmer, and Krogstad.   The gist of the play revolved around them.   Nora is the play’s heroine; the beautiful loving wife and doting mother.   Torvald is her husband, who works as a manager in a bank.   Then there is Krogstad, the character responsible for the past to slowly unfold and for the story to begin.   A few years back, when Torvald was sick, Nora was forced by circumstance to borrow money from Krogstad.   She kept that from Torvald, and she was scared for him to find out.   Now that Torvald is manager, he could now also fire Krogstad, who also works at the bank. Krogstad now threatens Nora that he will reveal her secret if she does not help him keep his job.   Nora then talks to her husband and tries to put in a good word for Krogstad, but to no avail.   Thus, the past is revealed to Torvald through the letter, and the real story begins.   Torvald is outraged, and begins calling Nora names.   What she has done is out of duty to her husband, being the obedient wife that she is.   Instead of thanking her, he greets her with anger.   Torvald is simply infuriated. By the time he forgives her, however, Nora has had a realization and decides his forgiveness no longer matters.   Nora undergoes a drastic transformation, a change in her individual persona that Torvald did not expect.   Hurwitt (2004) describes Nora as, â€Å"so animated in her kittenish sexuality, so maddeningly delightful in her teasing manipulations, and so punishingly fretful in her fear of discovery – that the stillness in her final disillusionment is enormously eloquent† (p. D-2).   Nora is the doll referred to in the title.   She was Torvald’s doll: she was his possession, his play thing.   She was under his control, and was extremely dependent on him.   Their home is the house; â€Å"the room is very much Nora’s dollhouse domain, as indicated†¦by the child’s table, chairs and tea set downstage† (Hurwitt, 2004, p. D-2). All her actions, decisions and choices are made by her husband, and she operates on his demands.   Everything she is involved in is mere play, because she is but an object.   His husband cannot even discuss serious matters with her because she herself is not taken seriously.   This is until she decides to leave everything behind and free herself from the prison that is her marriage.   She walks out the door and never looks back.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   Ironically, in contrast with Torvald’s treatment of her wife, the overall quality of the characters is serious, simply because it mirrored a serious social problem.   The majority of the play can be considered tragic, except the hopefulness described by Nora’s escape.   The characters are simple.   At the same time, they hold meaning and weight because not only are they telling the story of a problematic marriage, they are also trying to discuss gender issues. The other aspects of the play also helped in clearly conveying the message.   The language used was easy to understand.   It remained faithful to the language Ibsen used, one that was neither shallow nor overcomplicated, yet it revealed real life emotion.   It was â€Å"emotional, thematic, and metaphoric† (Hurwitt, 2004, p. D-2).   The stage set-up was also instrumental in bringing the message to the audience.   In a play, usually these things are overlooked.   Yet if one pays enough attention, the setting call also help tell the story and make the play come to life. Hurwitt (2004) observes, â€Å"A box constrained within boxes of social strictures, the Helmers’ tidy living room is redolent of the genteel poverty from which Nora dreams her husband’s new job as a bank manager will allow them to escape† (p. D-2).   The living room is then responsible for telling the viewers the social status of the family.   There were no special techniques used, no special music. With an already weighty play to speak of, it would be unnecessary to overembellish it.   In the instance of viewers, it was interactive in a sense; the play’s â€Å"deliberate pacing somewhat undercuts the tension, leaving room for audience members to make their own vocal contributions on opening night, rooting for Nora to get out and slam that door behind her† (Hurwitt, 2004, p. D-2).   The audience had been able to contribute to the play. In the end, Ibsen’s play is as personal as it is communal.   The family is the basic unit of society, and affairs between husband and wife are private matters.   Nonetheless, these matters are also influential in the social sphere, hinting that the problems of individuals are also characterized by issues in society.   Everyone should watch A Doll’s House because Henrik Ibsen’s masterpiece is as relevant then as it is now.   References Hurwitt, R. (2004, January 16). ACT draws out sexual politics in ‘Doll’s House.’ San Francisco Chronicle, p. D-2.

What Is a Second Order Reaction in Chemistry

A second order reaction is a type of chemical reaction that depends on the concentrations of one-second order reactant or two first-order reactants. This reaction  proceeds at a rate proportional to the square of the concentration of one reactant, or the product of the concentrations of two reactants.  How fast the reactants are consumed is called the reaction rate. Formulating General Chemical Reactions This reaction rate for a general chemical reaction aA bB → cC dD can be expressed in terms of the concentrations of the reactants by the equation: ï » ¿ratek[A]x[B]yrate k[A]x[B]yratek[A]x[B]yï » ¿ Here, k is a constant; [A] and [B] are the concentrations of the reactants; and x and y are the orders of the reactions determined by experimentation and not to be confused with the stoichiometric coefficients a and b. The order of a chemical reaction is the sum of the values x and y. A second order reaction is a reaction where x y 2. This can happen if one reactant is consumed at a rate proportional to the square of the reactants concentration (rate k[A]2) or both reactants are consumed linearly over time (rate k[A][B]). The units of the rate constant, k, of a ​second-order reaction are M-1 ·s-1. In general, second-order reactions take the form: 2 A → productsorA B → products. Examples of Second-Order Chemical Reactions This list of ten second-order chemical reactions features some reactions that are not balanced. This is because some reactions are intermediate reactions of other reactions. H OH- → H2OHydrogen ions and hydroxy ions form water. 2 NO2 → 2 NO O2Nitrogen dioxide decomposes into nitrogen monoxide and an oxygen molecule. 2 HI → I2 H2Hydrogen Iodide decomposes into iodine gas and hydrogen gas. O O3 → O2 O2During combustion,  oxygen atoms and ozone can form oxygen molecules. O2 C → O COAnother combustion reaction, oxygen molecules react with carbon to form oxygen atoms and carbon monoxide. O2 CO → O CO2This reaction often follows the previous reaction. Oxygen molecules react with carbon monoxide to form carbon dioxide and oxygen atoms. O H2O → 2 OHOne common product of combustion is water. This, in turn, can react with all the loose oxygen atoms produced in the previous reactions to form hydroxides. 2 NOBr → 2 NO Br2In the gas phase, nitrosyl bromide decomposes into nitrogen oxide and bromine gas. NH4CNO → H2NCONH2Ammonium cyanate in water isomerizes into urea. CH3COOC2H5 NaOH → CH3COONa C2H5OHIn this case, an example of the hydrolysis of an ester in the presence of a base, ethyl acetate in the presence of sodium hydroxide.