Answer:
Product A: cis; no
Product B: cis: no
Explanation:
Two common methods of forming oxiranes from alkenes are:
- Reaction with peroxyacids
- Formation of a halohydrin followed by reaction with base
1. Reaction with peroxyacids
(a) Stereochemistry
The reaction with a peroxyacid is a syn addition, so the product has the same stereochemistry as the alkene.
The starting alkene is cis, so the product is <em>cis</em>-2,3-diethyloxirane.
(b) Configuration
The product is optically inactive because it has an internal plane of symmetry.
It will not rotate the plane of polarized light.
2. Halohydrin formation
(a) Stereochemistry
The halogenation of the alkene proceeds via a cyclic halonium ion.
The backside displacement of halide ion by alkoxide is also stereospecific, so a cis alkene gives a cis epoxide.
The product is <em>cis</em>-2,3-diethyloxirane.
(b) Configuration
The cyclic halonium ion has an internal plane of symmetry, as does the product (meso).
The oxirane will not rotate the plane of polarized light.
Answer:
.54 mol
Explanation:
Using the ΔH given for the balanced reaction, convert kilojoules to moles of CO2 using the stoichiometric ratio:
250 kJ×(6 moles CO22803 kJ)=0.5351 moles CO2
The answer should have two significant figures, so round to 0.54 moles CO2.
Notice that coefficients in stoichiometric equations (indicating numbers of moles) are exact, so they do not constrain the number of significant figures.
Answer:
Avogadro's number represents the number of units in one mole of any substance. This has the value of 6.022 x 10^23 units / mole. This number can be used to convert the number of atoms or molecules into number of moles. We do as follows:
10 mol NH3 ( 6.022 x 10^23 molecules / 1 mol ) = 6.022x10^24 molecules NH3
A) carbohydrates
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Answer:
The number of moles of a primary standard can be determined from its formula weight and its mass. If a volumetric flask is used to carefully make up a standard solution from a primary standard, the concentration can be calculated by dividing the number of moles of solute by the volume of the flask in liters.
