3.07 Flame Test

In the last test, we had to test out a mystery powder (powder A, B, C), in its own separate test tube, in order to solve the Sherlock Holmes Mystery. Our group had powder C. When we mixed water in the mystery powder, it did not dissolve. When the litmus paper was put into the test tube it turned blue. When the vinegar was mixed it bubbled/foamed up. When we mixed the iodine solution, there was no reaction and the solution turned to a dark brown/black color. When we mixed in the baking soda there was no reaction and it turned to an even darker color.

this experiment had a similar scenario to part A except the metals were switched and replaced with

The primary goal of this laboratory is to correctly identify an unknown substance. To achieve this task, one may use various tests that reveal both chemical and physical properties of a substance. By comparing the results of a known substance and the unknown substance, one may eliminate alternative possibilities and more accurately predict the undisclosed compound. Furthermore, by performing these tests, data can be collected and verified regarding chemical and physical properties of the unknown. Understanding the chemical properties of a known substance aids one’s understanding of the unknown based on comparative analysis of the results of the tests.

13. A soft surface and a hard, smooth tool would most likely have which type of toolmark?

Examine a piece of nichrome wire. On the data sheet, record the color and the luster of the metal. Use a forceps to hold the wire in the flame of your burner for about two minutes (recall where the hottest part of the flame is located). Describe the appearance of the wire while held in the hottest part of the flame. Allow the wire to cool and reexamine it. From your observations, determine if there was a physical or a chemical change. Give specific reasons for your conclusions. Save the nichrome wire for step #2.

The white color implies that chlorine is within the mineral oil, thus did not react. Since chlorine did not react, it means that bromide isn’t a possible anion, leaving chlorine as the anion. In procedure 5, the unknown compound produced water on the watch glass indicating it could be a hydrate. The hydrate test was inconclusive because the number of waters of hydration shown in Table 5 was half way between being lithium chloride monohydrate and lithium chloride 2. The percent error, shown in Table 5, between the expected percent of water in lithium monohydrate and the accepted value, was high at 40% which meant that the unknown could not be properly identified as a hydrate. Repeating the hydrate test produced a similar percent which is shown in Table 7. The reason for these high percent errors is because lithium chloride and lithium monohydrate are both hygroscopic. In addition, Table 6 shows an increase in mass when unknown #42 was left outside, which suggest that the unknown compound is

Pour 50 mL of distilled water into a 100 mL beaker, and then add the unknown substance into it. Mix thoroughly to create the aqueous solution. Now fill a new cuvette with this new solution and place into the SpectroVis Plus device; after wiping the outside with a Kimwipe as usual. Be sure to take note of the absorbance when wavelength is at its maximum. Afterwards, Be sure to take all solutions containing Iron(III) and pour them into the container specified for hazardous wastes. ​

Eleven mystery test tubes labeled from K-1 to K-11 contained: 6M H2SO4, 6M NH3, 6M HCl, 6M NaOH, 1M NaCl, 1M Fe(NO3)3, 1M NiSO4, 1M AgNO3, 1M KSCN, 1M Ba(NO3)2, 1M Cu(NO3)2 respectively. The contents of the test tubes were determined by chemical experiments. Solution K-1 contained NiSO4 because when solution K-9, ammonia which was identified by its pungent odor, was added, an inky dark blue color was made. Iron (Fe (NO3)3) was determined to be in test tube K-2. KSCN was found in test tube K-11 since Fe (NO3)3 and KSCN makes a bloody color when mixed together. Flame tests were conducted in which K-8

Because it is dangerous to burn magnesium, it is not possible to directly record heat change. Our lab team suggests an indirect way of determining the heat of combustion for magnesium. To accomplish this, we need to perform two separate trials. One uses a solid (powder) version of MgO, while the other uses Mg ribbon. With the results from these, we can use Hess’ Law to determine q=∆H. This provides both a safe and successful way of indirectly determining the heat of combustion for magnesium.

2. If the mineral is non-metallic, decide if it is light or dark in color.

The objective of this lab was to use qualitative and quantitative measurements and observations to properly identify, and then confirm the identity of an unknown compound. After identification, the compound would have to be synthesized, in our case, through an acid-base reaction, followed by confirming its identity with the original unknown compound.

The flame test had a variety of results. Most of the known compounds did not match our unknown except for Ca(NO3)2. Both Ca(NO3)2 and the unknown compound had a deep red/orange color flame. While Ca(NO3)2 had the closest results two other compounds had slightly different results but not different enough to rule them out. Those other two compounds were CaCl2 with a yellow/ orange color and CaCO3 with a reddish color.

For example, silver nitrate formed a white precipitate when it was tested with ammonium chloride. In contrast, unknown 3 did not formed any precipitate with ammonium chloride. Ammonium chloride change the color of unknown 3 to a light green while the solution of silver nitrate and ammonium chloride was cloudy white solution. Likewise, the metal in unknown 3 could have been Calcium neither. Data and observation shows that calcium nitrate whether formed a white precipitate or did not react at all while unknown 3 formed an orange precipitate. Therefore, silver and calcium are not the two metal present in unknown

An unknown material can be determined by using simple chemical tests and separations which is called as inorganic qualitative analysis. The separation of cations depends on the difference in their propensity to form precipitates. Separation scheme is used to classify cation into five groups on the basis of their physical and chemical behavior opposed to some reagents. Classification is based on whether there is formation of precipitates or not when metal cations react with the reagent. The five groups of cations and the characteristics of these groups are as follows:

The colour of the precipitate was black and were quite small in size, so it was a bit hard to distinguish between the zinc powder present and the copper formed by the displacement reaction because copper formed should be reddish brown is colour – which is also a dark colour and thus two dark colours were hard to be distinguished.