Question 1-2 pic no.1-4 are the lab procedures and ans using to answer question

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Question 1-2

pic no.1-4 are the lab procedures and ans using to answer question 1-2

pic no.5 -Question paper

hydrogen gas you will use Dalton's Law of Partial Pressures. In this system, since we are collecting the hydrogen gas over water, the total pressure (barometric pressure) is: Pt PadgPwater vaor A second correction to the pressure will be necessary if you are unable to get the water level inside the collection cylinder exactly equal to the water level in the surrounding water bath. This situation will arise if the volume of gas generated is not enough to lower the water level inside the collection cylinder all the way down to the surrounding water bath and in this case the total pressure inside will be lower than the barometrie pressure provided. By measuring the distance between the two water levels you can correct for the difference in pressure by using the following relationship: Poeal inaide oylinder Petrs-Phigh coraetion with the height correction being 1.35 cm of water height difference- 1.00 torr pressure difference. 0.45 g Mg (three 0.15 g samples) 30 mL 3 M HCl (three 10 mL samples) 1. HCI solution (3 M) can cause serious skin and eye burns, use proper protection (gloves, apron and eyeware) and exercise caution. 2. The reaction of Mg metal with HCl is very exothermic. Keep the reaction cool by keeping the reaction tube in the water bath and slowly adding the HCl solution to the Mg turnings. 3. Be sure to point the test tube away from people during the gas evolution reaction, in the unlikely event that the pressure pops the stopper out violently. Wear your eye protection! PR 1. Accuratelyweigh 0.14 to 0.16 g magnesium turnings, record the mass and load into a large 25 mm x 150 mm test tube.. Fit the top of the test tube with a black neoprene stopper with two holes in it. One of the holes will already be fitted with a small lexible tube and the other open for now 2. At the sink, fill a large crystallizing dish half-full with water and completely fill a 250 mL 2graduated cylinder (GC) with water. Place your hand over the top of the GC (so as to prevent the water from leaking out when you invert it). Quickly invert the GC and place your hand and the top a filled water bath. Keeping the top of the GC under water, remove your hand. If you have 76

Explanation / Answer

Question 1

Answer : The following significant figures we need to calculate R

1) The Total Pressure = PHydrogen + Pwater vapour

2) The volume of gas generated

3) Water level difference inside and outside graduated cylender

The measurement that most limit our detemination of correct value of R is the Water level diffrence inside and outside graduated cylender because just 1.35 cm error in measuring the water level diffrence can change the value of pressure upto 1 Torr which highly effect the value of R.

Question 2

Answer : After the reaction of Mg with HCl the Hydrogen gas and MgCl2 is produced.All the HCl is added to the test tube so that no solid remains in the test tube and after complete reaction the H2 produced increase partial pressure and lower the water level so that exact value of R will be calculated.

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