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3 years ago

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

1 answer:

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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Please help me.. what is carbon 1/12

tatuchka [14]

Answer:

It is expressed as a multiple of one-twelfth the mass of the carbon-12 atom, 1.992646547 × 10−23 gram, which is assigned an atomic mass of 12 units. ... In this scale 1 atomic mass unit (amu) corresponds to 1.660539040 × 10−24 gram.

6 0

3 years ago

Find percent yield:

saveliy_v [14]

Answer: The percent yield of the reaction is 91.8 %

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

For $B_5H_9$ :

Given mass of $B_5H_9$ = 4.0 g

Molar mass of $B_5H_9$ = 63.12 g/mol

Putting values in equation 1, we get:

$\text{Moles of }B_5H_9=\frac{4g}{63.12g/mol}=0.0634mol$

For oxygen gas:

Given mass of oxygen gas = 10.0 g

Molar mass of oxygen gas = 32 g/mol

Putting values in equation 1, we get:

$\text{Moles of oxygen gas}=\frac{10g}{32g/mol}=0.3125mol$

The chemical equation for the reaction of $B_5H_9$ and oxygen gas follows:

$2B_5H_9+12O_2\rightarrow 5B_2O_3+9H_2O$

By Stoichiometry of the reaction:

12 moles of oxygen gas reacts with 2 moles of $B_2H_5$

So, 0.3125 moles of oxygen gas will react with = $\frac{2}{12}\times 0.3125=0.052mol$ of $B_2H_5$

As, given amount of $B_2H_5$ is more than the required amount. So, it is considered as an excess reagent.

Thus, oxygen gas is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

12 moles of oxygen gas produces 5 moles of $B_2O_3$

So, 0.3125 moles of oxygen gas will produce = $\frac{5}{12}\times 0.3125=0.130moles$ of water

Now, calculating the mass of $B_2O_3$ from equation 1, we get:

Molar mass of $B_2O_3$ = 69.93 g/mol

Moles of $B_2O_3$ = 0.130 moles

Putting values in equation 1, we get:

$0.130mol=\frac{\text{Mass of }B_2O_3}{69.63g/mol}\\\\\text{Mass of }B_2O_3=(0.130mol\times 69.63g/mol)=9.052g$

To calculate the percentage yield of $B_2O_3$ , we use the equation:

$\%\text{ yield}=\frac{\text{Experimental yield}}{\text{Theoretical yield}}\times 100$

Experimental yield of $B_2O_3$ = 8.32 g

Theoretical yield of $B_2O_3$ = 9.052 g

Putting values in above equation, we get:

$\%\text{ yield of }B_2O_3=\frac{8.32g}{9.052g}\times 100\\\\\% \text{yield of }B_2O_3=91.8\%$

Hence, the percent yield of the reaction is 91.8 %

6 0

4 years ago

Are s blocks metals ?

Mamont248 [21]

Yes, S-blocks are metals except for helium and hydrogen. The S-block metals are shiny, silvery and relatively soft, although they can easily lose electrons. Helium and hydrogen have valence electrons but also lack some similar properties as the other metals.

8 0

3 years ago

Mountains and valleys are some of the features found in the layer of rock at Earth's surface called the

loris [4]

Answer:

Narrow

Explanation:

Narrow

5 0

3 years ago

Some nonliving things that is found in earths environment use an example of how you use each thing

Gnoma [55]

Rocks, rocks can be used for many things depending on which rock you are talking about some rocks are used for construction of cement mixtures. Granite and marble are used for counter tops and desks depending on what district you go to school in and how funded the schools are there. pumice is a rock found in waters around volcanoes and is used to smooth organic surfaces such as feet. miscellaneous rocks are also used to prevent erosion. non living things can also include carbon which is the bases of life itself. Carbon is an organic element which is used in the synthesis medicines such as aspirin and poisons such as dichloromethane which is not used to poison others but is toxic to humans, it is mainly used for different isolation of unknown substances. Depending on what R grouping is attached to the carbon can be the deciding factor of how it can be used and how it can react with the environment. Elements like helium can be used in gas chromatograms and put into balloons

6 0

4 years ago