Please Help I will reward brainliest

how do we know that all the continents were all together at one point in time. writing prompt and it has to be at least 7 senten

kari74 [83]

Answer:

We can tell by how the continents look. Scientists who propose the pangea theory have said this. You can see for yourself because all the continents look like puzzle pieces you could put together. Scientists can also tell from the species. For example, let's say a scientist found a bone of a creature at the edge of a continent, the edge of another would have the same species. They have also calculated that the continents in itself are still splitting apart, but very slowly. The reason they split up was because tectonic plate movements.

5 0

3 years ago

Determine if each of the following statements about chiral molecules is True or False and select the best answer from the dropdo

oee [108]

Answer:

See explanation

Explanation:

-) True or False: All R stereocenters are dextrorotatory.

The absolute configuration is based is in specific rules that are not related to the ability to deflect polarized light. FALSE

-) True or False: Chiral centers in organic molecules will have 4 different groups attached to a carbon.

A chiral carbon by definition is a carbon with 4 groups. TRUE

-) True or False: A racemic mixture has an optical activity of 0.

In a racemic mixture, we have equal amounts of enantiomers, and this cancels out the optical activity. TRUE

-) True or False: Normal linear amines can be chiral centers.

In primary amines, we have 2 hydrogens. Therefore all the groups can not be different. So, is TRUE

-)True or False: Compound C has an optical activity of 0.

We need to know the structure of the compound

-)True or False: If the R isomer of a molecule has an optical rotation of + 25.7 degree then the S isomer of the molecule will have an optical rotation of -25.7 degree.

If we have the exact opposite (as we have in this case) the magnitud of the optical activity value will remain and the sign will change. TRUE

-)True or False: A CN is a higher priority than a CH2OH.

In this case, a carbon is directly bonded to the chiral carbon. The carbon on CN is bonded to a nitrogen atom and the carbon on CH2OH is bonded to an oxygen. So, the CH2OH will have more priority because O has a higher atomic number. FALSE

-)True or False: All molecules with chiral centers are optically active.

We can have for example mesocompounds in which the optical activity is canceled out due to symmetry planes. FALSE

-)True or False: To have an enantiomer a molecule must have at least two chiral centers.

A pair of enantiomers is made between at least 1 chiral carbon. Enantiomer R and enantiomer S. FALSE

-)True or False: Chiral molecules are always optically active.

We can have racemic mixtures or mesocompounds with chiral carbons but without optical activity. FALSE

-)True or False: A CH2CH2Br is higher priority than a CH2F.

The "Br" atom is bonded in the third carbon (respect to the chiral carbon) and the "F" atom is bonded to the second carbon. Therefore CH2F has more priority than CH2CH2Br. FALSE

-)True or False: Meso molecules with two stereocenters have a R,S configuration.

On the compounds with R and S configuration at the same time can have symmetry planes so, we will not have optical activity. TRUE

True or False: Diastereomers have the same physical properties except in a chiral environment.

All diastereomers have the same physical properties. TRUE

True or False: Compound H has an optical activity of 0.

We have to have the structure of the compound.

True or False: A C=C double bond is higher priority than a -CH(CH3)2.

In the case of C=C, we can say that is equivalent to two carbon bonds without hydrogens. Therefore C=C has higher priority. TRUE

6 0

4 years ago

Which one would it be since covalent bond is not here :( please help meeee

timurjin [86]

Non polar covalent bond. The Cl's electronegativity is the same since it's the same atom. Therefore, they will be nonpolar

5 0

3 years ago

Can someone please give me a simple equation on the mass of an isotope

frutty [35]

Mass 1 + %abundance of first isotope + Mass 2 + %abundance of second isotope
/ 100
This is RAM.

5 0

3 years ago

Please help!!!!its due tomorrow !!!

scZoUnD [109]

#6).
Every 1,000 mL makes 1 L
How many 1,000mL are there in 2,800 mL ?
That's division.
 (2,800 mL) / (1,000 mL) = 2.8 L

#7).
The 'perimeter' means the 'distance all the way around'.
You have to know that both sides of a rectangle are the same length,
and also the top and bottom are the same length.
So the perimeter of this rectangle is

 (2 yd) + (4.5 yd) + (2.yd) + (4.5 yd) = 13 yd .

Oops. The problem wants to know the perimeter in feet.
So you have to know that each yard is the same as 3 feet.
In order to find the number of feet in 13 yards, you have to
take 3 feet 13 times .

 (3 feet) times (13) = 39 feet .

#8).
For this one, you have to know that every 36 inches makes 1 yard.

How many 36 inches are there in 48 inches ?
That's division.
 (48 inches) / (36inches) = 1 and 1/2 yards .

#9).
For this problem, you have to know how to handle a mixed number,
and you also have to know that there are 16 ounces in 1 pound.

Add up the fruit:

 (3-1/2 pounds) + (4 pounds) + 2 pounds) = 9-1/2 pounds

Now, remember that each pound is the same as 16 ounces. So if you
want to find the number of ounces in 9-1/2 pounds, you have to take
16 ounces 9-1/2 times .

 (16 ounces) times (9-1/2) = 152 ounces.
___________________________________

#10).
This one is just adding up some numbers. But after you finish doing that, you have to know that 1,000 meters is called '1 kilometer' .

Add up the distances that Omar ran:

 (1,000 meters) + (1,625 meters) + (1,500 meters) = 4,125 meters

The problem wants to know how many kilometers this is, so you have to figure out how many '1,000 meters' fit into 4,125 meters.

That's division.

 (4,125 meters) / (1,000 meters) = 4.125 kilometers

4 0

4 years ago