Introduction In any science that requires computation, specifically in Chemistry, gathering measurements of various physical and chemical properties need to be strictly accurate and precise for it is in this most crucial phase that either make or break the quality and value of science. No matter how good the experiment was performed, without forethought on how to gather and process data correctly, the collected information would not be reliable enough to draw out a conclusion on it. This experiment is divided into two parts, thus having dipartite objectives for the whole experiment. In the first part, the main objective is to be able to identify accurately the identity of the unknown substance. The objective for the second part is to compute for the percent composition of the potassium chlorate in a mixture correctly. Stoichiometry is the branch of chemistry and chemical engineering that deals with the quantities of substances that enter into, and are produced by, chemical reactions. It is the accounting, or math behind, behind chemistry. Given adequate information, Stoichiometry can be used to calculate masses, moles, and percents within a chemical equation. Methodology A test tube containing 0.2 gram of manganese dioxide was weighed. After recording the data, 1 gram of the unknown substance was then added into the test tube and weighed again, the data recorded also. The test tube was heated using a gas burner and was held by the clamps of the iron stand. The heating continued until there was no more gas rising out of the mouth of the tube which signified that the chemical reaction had already ceased. The test tube was set aside, allowing it to cool to room temperature. When it had reached room temperature, it was weighed and the data recorded. After recording the weight of the test tube and its contents after heating, a second test tube was also weighed with 0.2 gram of manganese dioxide in it. The data was then recorded. A second unknown which is a mixture of potassium chlorate and potassium chloride weighing 2 grams was then placed on the test tube, it was weighed and the data recorded as well. It was held by the clamps on the iron stand and heated using the gas burner. Similar with the first part of the experiment, it was heated until there was no more gas ascending out of the test tube. It was allowed to reach room temperature. The test tube was the weighed and data recorded.
Compress the safety bulb, hold it firmly against the end of the pipette. Then release the bulb and allow it to draw the liquid into the pipette.
Diagram of Experiment Set-up. Prediction: My prediction is that if the amount of manganese dioxide, the powder. increases, there will be an increase in the rate of reaction. For example the highest concentration of powder will have the fastest reaction time.
The purpose of this lab was to calculate the percent composition by mass of oxygen in potassium chlorate.
The mixture was poured through a weight filter paper and Sucrose washed with a 5ml of dichloromethane. The resulting solid was left in a breaker to dry for one week, to be measured. Left it in the drawer to dry out for a week and weighted it to find the sucrose amount recovered amount.
One possible source of experimental error could be not having a solid measurement of magnesium hydroxide nor citric acid. This is because we were told to measure out between 5.6g-5.8g for magnesium hydroxide and 14g-21g for citric acid. If accuracy measures how closely a measured value is to the accepted value and or true value, then accuracy may not have been an aspect that was achieved in this lab. Therefore, not having a solid precise measurement and accurate measurement was another source of experimental error.
Experiment: First prepared a well plate with the appropriate amounts of distilled water, HCl, and Na2S2O3 in each well according to the lab manual. The well where the reaction
The Gravimetric Stoichiometry lab was a two-week lab in which we tested one of the fundamental laws of chemistry: the Law of Conservation of Mass. The law states that in chemical reactions, when you start with a set amount of reactant, the product should theoretically have the same mass. This can be hard sometimes because in certain reactions, gases are released and it’s hard to measure the mass of a gas. Some common gases released in chemical reactions include hydrogen, carbon dioxide, oxygen and water vapor. One of the best methods for determining mass in chemistry is gravimetric analysis (Lab Handout).
In a 100ml beaker 30mls of water was placed the temperature of the water was recorded. 1 teaspoon of Ammonium Nitrate was added to the water and stirred until dissolved. The temperature was then recorded again. This was to see the difference between the initial temperature and the final temperature.
By doing this experiment, I can know the physical and chemical properties of these samples. After I get my results about the physical and chemical properties of these samples, I can compare my results with the information given by the past student and identify the 5 unknown samples, finding out which sample is which substance. Hypothesis = ==
Science is a field that can be effected by many things. When conducting an experiment, uncertainty in is the unknown errors that could effect the results. Uncertainty is hard to account for because it cannot be predicted. Errors in science are the events that go wrong in the experiment which ultimately produce a difference between the true value and measured value. When executing an experiment there is always some type of error that is to be expected. Two types of error that are important to note are statistical error and systematic error. Statistical errors are bound to happen and cannot be compensated for. While on the other hand, systematic errors can be controlled and even
== = == Hypothesis for the experiment: After I conduct this experiment, I expect and suppose I can recognize and physical changes, identifying the difference these two kinds of changes. Also, I will be able to know some physical and chemical properties of copper (II) sulfate, water, iron, sodium carbonate, hydrochloric acid and magnesium and identify if it is a chemical change or physical change in each part of the experiment.
There is also the potential of human error within this experiment for example finding the meniscus is important to get an accurate amount using the graduated pipettes and burettes. There is a possibility that at one point in the experiment a chemical was measured inaccurately affecting the results. To resolve this, the experiment should have been repeated three times.
3. Why are the crucible and lid heated at the beginning of the experiment before being weighed?
Stoichiometry is a chemical branch that studies amounts of substances that are involved in reactions. Stoichiometry will help you to find out how much of the mixture you will need, or how much you started with. The calculations of a stoichiometry problem depends on a balanced chemical equations. The factors of the balanced equations signifies the molar ratio (the number of moles of each reactant needed to form a certain numbers of moles of each product) of the reactants and products taking part in the reaction. From the atomic and molecular point of view the stoichiometry in a chemical reaction is very simple. For example, one mole of oxygen reacts with two moles of hydrogen,
1. The labels have fallen off of three bottles thought to contain hydrochloric acid, or sodium chloride solution, or sodium hydroxide solution. Describe a simple experiment which would allow you to determine which bottle contains which solution.