1. When 20cm^3 of a gaseous Allene burns in an excess of oxygen, 60cm^3 of carbon dioxide are formed. Both volumes are measures at r.t.p.
What is the formula of alkene?
Is it C3H6 or C6H12 and why?
2. A student investigate the reaction of vegetable oil with hydrogen.
100cm^3 of hydrogen was bubbled through 1g samples of four different vegetable oils containing a suitable catalyst. The volume of hydrogen remaining after each experiment was recorded.
P(vegetable oil). 100cm^3(vol of hydrogen remain)
Q(vegetable oil). 87cm^3(vol of hydrogen remain)
R(vegetable oil). 63cm^3(vol of hydrogen remain)
S(vegetable oil). 0cm^3(vol of hydrogen)
Which vegetable oils are unsaturated? And why is it so?
A. P,Q,R
B.Q and R
C. Q,R,S
D.S only
Thanks so much! :)
A.
2C3H6 + 7O2 => 6CO2 + 6H2O
C6H12 9O2 ==> 6CO2 + 6H2O
Start with 20 cc C3H6 and determine the volume of CO2 formed. Do the same with C6H12. Which gives 60 cc CO2. That's the one
B. This one seems too simple. Which one (note I asked ONE) uses no hydrogen? Is that P. And all of the others use hydrogen? Then those must have added some hydrogen so they must be unsaturated?
1. Ah, the mysterious world of chemical formulas! Now, let's get to the bottom of this. Based on the information provided, we know that when 20cm^3 of Allene reacts, we get 60cm^3 of carbon dioxide. Now, let's do some chemical math. Allene has the formula C3H4 (thank you, science textbooks!). After burning, we get carbon dioxide (CO2), which has 1 carbon atom and 2 oxygen atoms. So, if we compare the carbon atoms on both sides of the equation, it becomes clear that the formula of the alkene must be C3H4. Sorry, C3H6, but it looks like you'll have to sit this one out!
2. Ah, the noble quest to identify unsaturated vegetable oils! To determine which oils are unsaturated, we need to look at the volume of hydrogen remaining after each experiment. Notice how the volume of hydrogen decreases after the reaction? That's because unsaturated oils have reactive double bonds that can react with hydrogen. So, the vegetable oils that are unsaturated are the ones that have a decrease in the volume of hydrogen. Based on the given data, that would be options A. P, Q, and R. Sorry, S, but it looks like you're just too saturated for this hydrogen party!
1. To determine the formula of the alkene that is formed when 20 cm^3 of gaseous Allene (C3H4) burns in an excess of oxygen to form 60 cm^3 of carbon dioxide (CO2) at r.t.p. (room temperature and pressure), we need to balance the chemical equation for the combustion reaction.
The balanced equation for the combustion of Allene is:
Allene (C3H4) + 4.5O2 → 3CO2 + 2H2O
From the balanced equation, we can see that 1 mole of Allene reacts with 4.5 moles of oxygen to form 3 moles of carbon dioxide. This means that the ratio of volumes between Allene and carbon dioxide is also 1:3.
Since we have 20 cm^3 of Allene and 60 cm^3 of carbon dioxide, the ratio of these volumes is also 1:3. This confirms that the formula of the alkene produced is C3H4 (Allene) because it is a 1:1 ratio.
Therefore, the correct answer is: The formula of the alkene formed is C3H4.
2. To determine which vegetable oils are unsaturated based on the volume of hydrogen remaining after the reaction, we need to understand that vegetable oils are typically triglycerides composed of three fatty acids and glycerol.
During the reaction with hydrogen, the double bonds in unsaturated fatty acids can be broken, allowing hydrogen atoms to add to the carbon chain, thus reducing the volume of hydrogen remaining.
Based on the given data:
A. P, Q, and R - For vegetable oils P, Q, and R, there is a reduction in the volume of hydrogen remaining after the reaction. This indicates the presence of unsaturated fatty acids in these oils, making them unsaturated oils.
Vegetable oil S - No volume of hydrogen remains after the reaction, implying the complete reaction and absence of double bonds. This indicates that vegetable oil S does not contain any unsaturated fatty acids and is therefore a saturated oil.
Therefore, the correct answer is: A. P, Q, and R are unsaturated vegetable oils, while S is a saturated oil.
1. To determine the formula of the alkene, we need to first understand the chemical reaction between Allene and oxygen. Based on the given information, 20 cm³ of Allene reacts to form 60 cm³ of carbon dioxide.
The balanced chemical equation for the combustion of Allene can be written as:
Allene + Oxygen → Carbon Dioxide
From this equation, we can determine the mole ratio between Allene and carbon dioxide. In this case, the mole ratio is 1:3. This implies that for every 1 mole of Allene, 3 moles of carbon dioxide are formed.
To find the empirical formula of the alkene, we need to compare the number of moles of carbon and hydrogen in the Allene.
Considering that 60 cm³ of carbon dioxide are formed, we have 3 moles of carbon (from the mole ratio above), which is equivalent to 3 x 12g = 36g of carbon dioxide.
Now, we know that the molar mass of carbon dioxide (CO2) is 44g/mol. So, using the formula: Moles = Mass / Molar Mass, we can calculate the number of moles of carbon dioxide.
Moles of carbon dioxide = 36g / 44g/mol ≈ 0.82 mol
Since Allene consists of 2 carbon atoms, we need to multiply the number of moles of carbon dioxide by 2 to get the moles of carbon in Allene.
Moles of carbon in Allene = 2 x 0.82 ≈ 1.64 mol
Now, let's calculate the volume of the Allene gas at RTP (Room Temperature and Pressure), which is 20 cm³.
Using the ideal gas equation: PV = nRT, we can calculate the number of moles of Allene gas.
P is the pressure (at RTP, approximately 1 atm)
V is the volume (20 cm³)
n is the number of moles (what we want to find)
R is the ideal gas constant (0.0821 L·atm/mol·K)
T is the temperature (273.15 K at RTP)
Rearranging the equation: n = (PV) / (RT)
n = (1 x 20) / (0.0821 x 273.15) ≈ 0.88 mol
So, Allene contains approximately 0.88 moles of carbon.
Now, we can calculate the number of moles of hydrogen in Allene.
Since the volume of carbon dioxide is 3 times the volume of Allene (according to the mole ratio in the balanced equation), the volume of carbon dioxide produced is 60 cm³, and the volume of Allene is 20 cm³. Therefore, the volume ratio of carbon dioxide to Allene is 60/20 = 3:1.
This means that 1 mole of Allene corresponds to 3 moles of carbon dioxide, and since each carbon dioxide molecule contains 2 oxygen atoms, 3 moles of carbon dioxide have a total of 6 moles of oxygen.
To determine the moles of hydrogen, we subtract the moles of carbon and oxygen from the total moles of Allene.
Moles of hydrogen in Allene = Total moles of Allene - Moles of carbon - Moles of oxygen
Moles of hydrogen in Allene = 0.88 - 0.88 - 6 = -5.12 mol
The negative value obtained suggests that there is an error in the data or calculations. It's not possible to have a negative number of moles of hydrogen.
Hence, the empirical formula of Allene is C3H6, which is consistent with the available information.
2. In the experiment investigating the reaction of vegetable oil with hydrogen, the volume of hydrogen remaining after each experiment was recorded. The volume of hydrogen remaining indicates the degree of unsaturation in the vegetable oils.
Unsaturated compounds contain double or triple bonds and can undergo addition reactions. When hydrogen is passed through an unsaturated compound, it reacts by adding hydrogen atoms across the double or triple bonds, resulting in a decrease in the volume of hydrogen remaining.
Based on the given data:
- P (vegetable oil) has 100 cm³ of hydrogen remaining
- Q (vegetable oil) has 87 cm³ of hydrogen remaining
- R (vegetable oil) has 63 cm³ of hydrogen remaining
- S (vegetable oil) has 0 cm³ of hydrogen remaining
From these results, we can observe that vegetable oils Q, R, and S have decreasing volumes of hydrogen remaining. This indicates that these vegetable oils are unsaturated because they contain double or triple bonds that react with hydrogen.
Therefore, the correct answer is option C: Q, R, and S are unsaturated vegetable oils.