Answer:
Percentage yield = 30%
Explanation:
Given data:
Number of moles of NO = 7.0 mol
Number of moles of O₂ = 5 mol
Number of moles of NO₂ = 3 mol
Percentage yield = ?
Solution:
Chemical equation:
2NO + O₂ → 2NO₂
Now we will compare the moles of NO₂ with NO and O₂ .
NO : NO₂
2 : 2
7.0 : 7.0
O₂ : NO₂
1 : 2
5.0 : 2 ×5.0 = 10 mol
The number of moles of NO₂ produced by NO are less it will be limiting reactant.
Mass of NO₂ = moles × molar mass
Mass of NO₂ = 10 mol × 46g/mol
Mass of NO₂ = 460 g
Actual yield of NO₂:
Mass of NO₂ = moles × molar mass
Mass of NO₂ = 3 mol × 46g/mol
Mass of NO₂ = 138 g
Percentage yield:
Percentage yield = Actual yield/theoretical yield × 100
Percentage yield = 138 g/ 460 g × 100
Percentage yield = 30%
First, recognize that this is an elimination reaction in which hydroxide must leave and a double bond must form in its place. It is likely an E2 reaction. Here is an efficient mechanism:
1) Pre-reaction: Protonate the -OH to make it a good leaving group, water. H2SO4 or any strong H+ donor works. The water is positively charged but still connected to the compound.
2) E2: Use a sterically hindered base, such as tert-butoxide (tButO-) to abstract the hydrogen from the secondary carbon. [You want a sterically hindered base because a strong, non-sterically hindered base could also abstract a hydrogen from one of the two methyl groups on the tertiary carbon, and that leads to unwanted products, which is not efficient]. As the proton of hydrogen is abstracted, water leaves at the same time, creating an intermediate tertiary carbocation, and the 2 electrons in the C-H bond immediately are used to make a double bond towards the partial positive charge.
In the products we see the major product and water, as expected. Even though you have an intermediate, remember that an E2 mechanism technically happens in one step after -OH protonation.
The answer is D. To put it simply, all atom wished to become stable. The only way for that is to obtain an octet structure where the outermost shell would have 8 electrons, thus being full.
The average speed is 0.28
