Experiment Pre-Lab Questions Describe the technique for testing the odor of a ga

Question

Experiment Pre-Lab Questions Describe the technique for testing the odor of a gas. why? What precautions must be taken and 2 Fill in the blanks: A gas is tested with moist red litmus paper. No color change is observed. It is then . tested with moist blue litmus paper. The paper turns red. The gas is . Another gas is tested the same way. The gas did not change the color of either the red or blue litmus paper. The gas is 3. The following reagents were used to produce various nonmetal species Identify the likely species prepared. Indicate whether it is an element, oxide or hydride. · Sodium carbonate Ammonium chloride Potassium iodide . Thioacetamide Hydrogen peroxide 4. An unknown substance in aqueous solution is treated with various reagents including hexane, a colorless liquid less dense than water. The test tube is stoppered and shaken. The upper layer remains colorless. Name two nonmetal specics that can mot be present in the unknown. Explain your answer. 5. An unknown substance in aqueous solution is treated with various reagents. A strong degree of effervescence is observed. Identify the non-metal species may have been formed. Write an equation for one of the reactions that would produce the effervescence 39

Explanation / Answer

1. the odour of a gas can be tested by first diluting it with an inert gas such as Ar or N2 and then smelling the gas. Precaution must be taken as most of the gases are toxic and may cause serious health damage.

2.

When the blue litmus turns red, it indicates the gas is acidic.

When neither the blue not the red litmus showed any color change, the gas is neutral/inert.

3. Reagents used to prepare nonmetal species

sodium carbonate : produces carbon dioxide an oxide

ammonium chloride : Produces ammonia which is a hydride

potassium iodide : produces iodine an element

thioacetamide : produces sulfur an element

hydrogen peroxide : produces oxygen an element

4. Nonmetal species such as HCl and NH3 are insoluble in hexane. The species are polar in nature whereas, hexane is non-polar therefore the two are imiscible with each other.

5. The nonmetal species which is a gas could be CO2.

A general reaction could be,

RCO2H + NaHCO3 ---> RCO2Na + H2O + CO2(gas)

3.

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