1.2 x 5 = 6
1 x 5 = 5
The ratio of Mg to O is therefore 6:5
The empirical formula of Magnesium Oxide found for this trial is therefore Mg6O5
Trail 1.
Observations:
(Observations are made by lifting the lid after every 2 minutes)
1. Nothing.
2. Nothing but crucible glows red at the bottom.
3. Little smoke, sparkle and white bubbles.
4.White smoke .
5.Fire inside.
6.Glow, white smoke and flame.
7.Black and white crumples on metal.
8. Less flame.
9. No flame but it glows.
10. Less sparks and less glow.
11.Little smoke.
12.No smoke(white fluid material and residue on lid).
13. No further reaction.
Raw Data:
Initial mass of crucible with lid ( in grams) + 0.0001= 24.1874g
Mass of magnesium inside crucible with the lid ( in grams) + 0.0001 =24.5431g
Final mass of (MgO) inside crucible with lid in grams + 0.0001=24.7389g
Processed Data:
Percentage uncertainty= 0.04%
1.Mass of magnesium (in grams) + 0.0001= 0.3557g
(The mass of magnesium ribbon = The mass of the crucible, lid and magnesium- mass of the crucible and lid)
2.Mass of oxygen that combine with Mg ( in grams) +0.0001= 0.1958g
(Mass of oxygen = mass of magnesium oxide, crucible, lid - mass of magnesium, crucible, lid)
3.Number of moles of magnesium. = 0.01464Mole
(the number of moles of magnesium = mass / atomic weight . The atomic weight of magnesium is 24.3 g / mole )
4.Number of moles of oxygen atoms that were used. = 0.0122Mole
(the number of moles of oxygen = mass / atomic weight . The atomic weight of magnesium is 16.0 g / mole )
5.Simplest ratio: Mg = 0.01464Mole = 1.2
0.0122Mole
Oxygen = 0.0122mole = 1
0.0122mole
Multiply by the smallest whole number you can possibly find to get whole number:
1.2 x 5 = 6
1 x 5 = 5
The ratio of Mg to O is therefore 6:5
The empirical formula of Magnesium Oxide found for this trial is therefore Mg6O5
Trail 2:
Observations:
(Observations are made by lifting the lid after every 2 minutes)
1. Nothing.
2. Nothing but crucible glows red at the bottom.
3. White smoke .
4. Flame inside and lots of white smoke(fumes).
5. Sparkles and less smoke.
6. Smoke and white bumps on the metal.
7. Smoke.
8. Little smoke.
9. No smoke(white fluid material and residue on lid).
10. No further reaction.
Raw Data:
Initial mass of crucible with lid ( in grams) + 0.0001= 32.9232g
Mass of magnesium inside crucible with the lid ( in grams) + 0.0001 =33.1472g
Final mass of (MgO) inside crucible with lid in grams + 0.0001=33.2711g
Mass of MgO inside crucible with lid in grams after ´heating to constant mass`=33.2605g
Processed Data:
Percentage uncertainty= 0.04%
1.Mass of magnesium (in grams) + 0.0001= 0.2240g
(The mass of magnesium ribbon = The mass of the crucible, lid and magnesium- mass of the crucible and lid)
2.Mass of oxygen that combine with Mg ( in grams) +0.0001= 0.1133g
(Mass of oxygen = mass of magnesium oxide, crucible, lid - mass of magnesium, crucible, lid)
3.Number of moles of magnesium. = 0.0091 Mole
(the number of moles of magnesium = mass / atomic weight . the atomic weight of magnesium is 24.3 g / mole )
4.Number of moles of oxygen atoms that were used. = 0.0071mole
(the number of moles of oxygen = mass / atomic weight . the atomic weight of magnesium is 16.0 g / mole )
5.Simplest ratio: Mg = 0.0151 Mole = 1.33
0.0135mole
Oxygen = 0.0135mole = 1
0.0135mole
Multiply by the smallest whole number you can possibly find to get whole number:
1.33 x 3 = 4
1 x 5 = 3
The ratio of Mg to O is therefore 4:3
The empirical formula of Magnesium Oxide found for this trial is therefore Mg4O3
Trail 4.
Observations:
(Observations are made by lifting the lid after every 2 minutes)
1. Nothing.
2. Nothing but crucible glows red at the bottom.
3. White smoke.
4. Sparks and glow.
5. Little smoke, sparkle.
6.Fame and white fumes.
7.Glow, white smoke and flame.
8. Magnesium ribbon half burned and there is flame inside.
9. No flame but it glows.
10.Less sparks and less glow.
11.White fumes.
12. Wispy fumes.
13. No smoke(white fluid material and residue on lid).
14. No further reaction.
Raw Data:
Initial mass of crucible with lid ( in grams) + 0.0001= 32.9220g
Mass of magnesium inside crucible with the lid ( in grams) + 0.0001 =33.1552g
Final mass of (MgO) inside crucible with lid in grams + 0.0001=33.2811g
Mass of MgO inside crucible with lid in grams after ´heating to constant mass`=33.2725g
Processed Data:
Percentage uncertainty= 0.04%
1.Mass of magnesium (in grams) + 0.0001= 0.2332g
(The mass of magnesium ribbon = The mass of the crucible, lid and magnesium- mass of the crucible and lid)
2.Mass of oxygen that combine with Mg ( in grams) +0.0001= 0.1173g
(Mass of oxygen = mass of magnesium oxide, crucible, lid - mass of magnesium, crucible, lid)
3.Number of moles of magnesium. = 0.0090Mole
(the number of moles of magnesium = mass / atomic weight . The atomic weight of magnesium is 24.3 g / mole )
4.Number of moles of oxygen atoms that were used. = 0.0080Mole
(the number of moles of oxygen = mass / atomic weight . The atomic weight of magnesium is 16.0 g / mole )
5.Simplest ratio: Mg = 0.0096Mole = 1.2
0.0080Mole
Oxygen = 0.0080mole = 1
0.0080mole
Multiply by the smallest whole number you can possibly find to get whole number:
1.2 x 5 = 6
1 x 5 = 5
The ratio of Mg to O is therefore 6:5
The empirical formula of Magnesium Oxide found for this trial is therefore Mg6O5
Trail 5.
Observations:
(Observations are made by lifting the lid after every 2 minutes)
1. Nothing.
2. Nothing but crucible glows red at the bottom.
3. Little smoke, sparkle and white bubbles.
4.White smoke .
5.Fire inside.
6.Glow, white smoke and flame.
7.Black and white crumples on metal.
8. Less flame.
9. No flame but it glows.
10. Less sparks and less glow.
11.Little smoke.
12.No smoke(white fluid material and residue on lid).
13. No further reaction.
Raw Data:
Initial mass of crucible with lid ( in grams) + 0.0001= 27.6400g
Mass of magnesium inside crucible with the lid ( in grams) + 0.0001 =27.9850g
Mass of MgO inside crucible with lid in grams after ´heating to constant mass`=28.2125g
Processed Data:
Percentage uncertainty= 0.04%
1.Mass of magnesium (in grams) + 0.0001= 0.3450g
(The mass of magnesium ribbon = The mass of the crucible, lid and magnesium- mass of the crucible and lid)
2.Mass of oxygen that combine with Mg ( in grams) +0.0001= 0.2275g
(Mass of oxygen = mass of magnesium oxide, crucible, lid - mass of magnesium, crucible, lid)
3.Number of moles of magnesium. = 0.0149Mole
(the number of moles of magnesium = mass / atomic weight . The atomic weight of magnesium is 24.3 g / mole )
4.Number of moles of oxygen atoms that were used. = 0.0142Mole
(the number of moles of oxygen = mass / atomic weight . The atomic weight of magnesium is 16.0 g / mole )
5.Simplest ratio: Mg = 0.0142Mole = 1
0.0142Mole
Oxygen = 0.0142mole = 1
0.0142mole
The ratio of Mg to O is therefore 1:1
The empirical formula of Magnesium Oxide found for this is MgO
CONCLUSION AND EVALUATION
Conclusion:
The weight of the product (MgO) produced is more than Mg used as it combines with Oxygen resulting in increase in the mass. The empirical formula of magnesium oxide is MgO
For trail 5, the empirical formula of magnesium oxide is MgO. For other trails , the empirical formula of magnesium oxide is Mg6O5. Based on the data processing in trail run, 1,2,3,4 the Mg/O ratio of 1.2 and I would have conclude from my experiment that the empirical formula of magnesium oxide is Mg6O5 . My method for determining this is as follows:
Explanation of conclusion: If the Mg/O ratio is 1.2, that means that the empirical formula would be Mg1.2 O. Obviously you cannot have a non-integral number in a chemical formula and 1.2 is too far to round down to 1.00, but multiplying it by 5 gives 6. If you multiply Mg by 5, you must do the same to O, so the formula must be Mg6O5.
However, I know from the literature value of Mg/O = 1.00,because the reaction between magnesium and oxygen creates magnesium oxide, an ionic compound. Since the magnesium cation has a +2 charge and oxygen anion has a -2 charge, the real formula would have to be MgO, resulting in an Mg/O ratio of 1. Therefore, something is wrong with my experiment as in the trails which I performed the Mg/O ratio is 1.2, that means that the empirical formula would be Mg6O5.
Therefore Percentage error = 2% and Percentage uncertainty= 0.04%
The percentage error of 2% is larger than the experimental uncertainty of 0.04%, so there must be significant systematic error. Furthermore, because the percent error is positive, that means that there is either too much Mg or too little O. That is the only way that the ratio of Mg/O could be larger than 1.00
The most likely cause of this error was the fact that the procedure had us lift the lid of
the crucible and look inside to check and see if the reaction was finished every two
minutes. When I lifted the lid of the crucible, some white smoke escaped. This was
our product, magnesium oxide. Since we had already recorded the mass of the
magnesium before the reaction started, any loss of product would make it appear as
though oxygen was lost. It would, in effect, make the oxygen part of the Mg/O ratio
too small and thereby produce a Mg/O ratio larger than 1.00
The weaknesses that could have caused this specific error, such as accidentally losing some of the product when moving the crucible to the balance to weight it. The time interval for lifting the lid was not accurate. The magnesium ribbon was not properly cleaned so may contain coating of MgO.The lid might have been off for too long so magnesium oxide product would have escaped. May be the lid is not placed properly on the crucible. There are some uncertainties in weighing it. It took long time to place lid back on the crucible as we were not able to lift the lid with the tong and even one lid fell down and broke.
Realistic modification to the experiment that explicitly addresses the error(s)/weakness(s) that I identified:
The magnesium ribbon should be cleaned using the emery paper. The proper caution should be taken while weighing the product and insure that reading on measuring balance is zero before you weigh it. After lifting the lid, cover the crucible properly with the lid to prevent the loss of the product. Practise lifting the lid before conducting experiment so that lid is placed back on the crucible quickly. While it is necessary to lift the lid to allow some oxygen to get in and to see if the reaction is finished, and therefore some loss of product is unavoidable, I do not think that the procedure made it clear just what impact this could have on the results. I also think that checking every two minutes was excessive. Therefore, in the future I think that this error could be minimized by placing an explicit warning in the procedure and by increasing the checking time to every five minutes instead of two. The only solution to this problem would be to ensure that the lid is on the crucible and to carry it as carefully as possible to prevent the loss of the product.
