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Sindrei [870]
3 years ago
14

The three end stages of stars are Red Giant Phase, Second Red Giant Phase and White Dwarf Phase correct?

Chemistry
1 answer:
solong [7]3 years ago
6 0

Answer: Most of the stars in the universe are main sequence stars — those converting hydrogen into helium via nuclear fusion. A main sequence star may have a mass between a third to eight times that of the sun and eventually burn through the hydrogen in its core. Over its life, the outward pressure of fusion has balanced against the inward pressure of gravity. Once the fusion stops, gravity takes the lead and compresses the star smaller and tighter.

Temperatures increase with the contraction, eventually reaching levels where helium is able to fuse into carbon. Depending on the mass of the star, the helium burning might be gradual or might begin with an explosive flash.

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Which of these has the most covalent character? <br> NaF Caf2 Bef2 CsF SrF2
Ksenya-84 [330]

Thus BeF2 is of most covalent character.

Anyways, covalent/ionic character is a bit tricky to figure out; we measure the difference in electronegativity of two elements bonding together and we use the following rule of thumb: if the charge is 0 (or a little more), the bond is non-polar covalent; if the charge is > 0 but < 2.0 (some references say 1.7), the bond is polar covalent; if the charge is > 2.0 then the bond is ionic. Covalent character refers to smaller electronegativity difference while ionic character refers to greater electronegativity difference.


Now, notice all of our bonds are with F, fluorine, which has the highest electronegativity of 3.98. This means that to determine character we need to consider the electronegativities of the other elements -- whichever has the greatest electronegativity has the least difference and most covalent character.
Na, sodium, has electronegativity of 0.93, so our difference is ~3 -- meaning our bond is ionic. Ca, calcium, has 1.00, leaving our difference to again be ~3 and therefore the bond is ionic. Be, beryllium, has 1.57 yielding a difference of ~2.5, meaning we're still dealing with ionic bond. Cs, cesium, has 0.79, meaning our difference is again ~3 and therefore again our compound is of ionic bond. Lastly, we have Sr, strontium, with an electronegativity of 0.95 and therefore again a difference of roughly 3 and an ionic bond. <span>
</span>
3 0
3 years ago
A block of iron has a mass of 826 g. What is the volume of the block of iron whose density at 25°C is 7.9 ?
kolezko [41]

Answer:

104.56cm³

Explanation:

Mass=826g

Density =7.9g/cm³

Volume =Mass /Density

Volume =826/7.9

Volume =104.56cm³

5 0
2 years ago
The mass of 1.63x10^21 silicon atoms is how many grams
gladu [14]
<span>Lyle stirs 5.0 grams of salt into a beaker of water. He then adds 15.0 grams of pure iodine to the mixture. If the total mass of the new mixture is 225 grams, what is the mass of the water
</span>

6 0
3 years ago
PLEASEEEEE PLEASEEEEE ANSWER THIS QUESTION ILL GIVE BRAINLIEST AND 15 POINTSSSSS plzzzz!!!!!
zalisa [80]

Answer:

D

Explanation:

A and B are completely wrong and C is partial but D is the best option

6 0
3 years ago
Read 2 more answers
An 18-g sample of element A combines completely with a 4-g sample of element B to form the compound AB. What is the mass of the
DaniilM [7]

Answer:

22g

Explanation:

Given parameters:

Mass of element A = 18g

Mass of element B  = 4g

Unknown:

Mass of compound formed = ?

Solution:

 The reaction equation is given as;

          A   +   B   →  AB

According to the law of conservation of mass "in a chemical reaction, matter is neither created nor destroyed but changed from one form to another".

Simply mas is conserved and the mass of the reactants is the same as the mass of the product that forms.

  Mass of reactants  = mass of A + mass of B = 18g + 4g  = 22g

 So;

  Mass of product AB = 22g

6 0
2 years ago
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