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CHM110 Experiment 3 Report.docx

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University of Toronto Mississauga
Judith C Poe

P a g e | 1 Purpose: I. The purpose of the first part of the lab was to determine the atomic mass of a metallic element by reacting with an aqueous acid of known concentration. Through quantitative analysis products of the reaction were analyzed and the atomic mass of the unknown solution was calculated. In this experiment, the atomic mass of unknown element will be found by determining the moles of H gas produced by a known weight of the unknown metal. Then, by calculating using 2 the stoichiometric ratio, the moles of the metal that reacted was found which eventually helped in determining the atomic mass II. The second part of the experiment was designed to determine the relative rates of diffusion of the gases hydrogen chloride and ammonia by measuring the distance travelled by the two gases in the same amount of time. During the experiment, both the gases were introduced at either ends of the hollow glass tube from where the gases start to diffuse towards each other. The resulting white ring of ammonium chloride indicated the point of reaction of two gases and the relative distances were measured to and calculated to find the rates of diffusion. Rates of diffusion were calculated by using: √ Experimental method: 1 I. Please refer to the lab manual P a g e | 2  No deviations were taken from the lab manual Results: [For all error analysis, refer to the appendix. For all numerical constants, refer to reference 3 (Haynes, 2012)] A. G ASES Table 1.1 Experimental Data for 3 different trials Trial # Length of tube Distance of Ring of N4 Cl from Cotton in NH 3nd of tube HCl end of tube 1 47.4 28.3 19.1 2 47.2 27.8 19.4 3 47.4 27.5 19.9 Average distance travelled 27.8 19.5 The theoretical rate of diffusion can be calculated by using the below stated equation where √ √ Through experiment, the rate was determined to be, | | P a g e | 3 B. D ETERMINING THE ATOMIC MASS OF UNKNOWN METAL To determine the Hydrostatic pressure: Therefore, by using the relation , the Hydrostatic pressure was found to be To determine the moles of hydrogen gas, P a g e | 4 Let n = 2 Since n = 2 the balanced chemical equation can be written as follows Mass of unknown metal = 0.0203g ± 0.00005g Therefore, the atomic mass of the unknown metal can be calculated as follows: Let n = 3 Since n = 3 the balanced chemical equation can be written as follows Mass of unknown metal = 0.0203g ± 0.00005g Therefore, the atomic mass of the unknown metal can be calculated as follows: P a g e | 5 Discussion and conclusion In the first part of the experiment, the metal reacted with Hydrochloric acid to produce Hydrogen gas and water vapor. Through the calculation, the metal was found to be magnesium. Magnesium (Mg) has an oxidation state of +2 which means when it reacts with an acid to releases 2 electrons into the solution to attain a stable octet structure . 2 (Half Equations ) Likewise, addition of Hydrochloric acid (HCl) in water causes the Hydrogen atom to react with water, which acts as a base in this situation and results in dissociation of hydrogen from chlorine and forms a bond with the water molecule to form a hydronium ion (H O ) and a3chlorine ion (Cl) - (Half Equations ) Furthermore, the electrons that were released by magnesium react with the hydronium ions in the solution to maintain the neutrality of the solution. (Half Equations) As a result of the above mentioned redox reaction, Hydrogen gas is produced which was collected in the gas burette by the downward displacement of the solution while are dissolved in the solution as ions . 2 Despite the reaction taking place in water, the metal does not react with water because the electrons released by Magnes
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