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Fynjy0 [20]
3 years ago
9

Consider the Hertzsprung Russell diagram seen here. We can use this diagram to classify stars and determine their characteristic

s.
The color of a star is determined by its temperature: the hottest stars are blue and the coolest are red. The Sun has a surface
temperature of 5,500°C and it appears yellow. The diagram also indicates that temperature coincides with luminosity: the hotter the
star, the higher the luminosity. You can also tell the size of each star from the graph as the larger the radius, the higher the
temperature and luminosity. Regardless of a star's position in the diagram, the energy that results in high temperatures and the stars
luminosity is generated by what process?
W
A)
nuclear fusion
B)
nuclear fission
gravitational forces of swirling gases
D)
friction generated by gravitational force

Chemistry
1 answer:
Ann [662]3 years ago
5 0

Answer:

Explanation:

A- nuclear fusion

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If the density of water is 1g/ml, what is the mass of 254ml of water?
Mariulka [41]
The mass of 254 mL of water is 254 g. Since the density of water is 1g/mL, we can simply multiply the density 1g/mL by 254 mL of water and get 254 g as our answer.  Since mL is in the numerator and denominator, mL cancels out and we are left with g only. 
8 0
3 years ago
Predict whether ΔS° is greater than, less than, or approximately zero for each of the following reactions, and explain your choi
inna [77]

Answer:

Explanation:

Entropy -

In a system, the randomness is measured by the term entropy .

Randomness basically refers as a form of energy that can not be used for any work.

The change in entropy is given by amount heat per change in temperature.

  • When solid is converted to gas entropy increases,

As the molecules in solid state are tightly packed and has more force of attraction between the molecules, but as it is converted to gas, the force of attraction between the molecule decreases and hence entropy increases.

So,

The particles of the substance , if are tightly held by strong force of attraction will decrease the entropy ,

And

If the particles are loosely held , the entropy will increase .  

  • If in a reaction , more number of gaseous atoms are present in the product side , entropy will increase , i.e. Δ°S > 0
  • When liquid is converted to solid entropy decreases,  

As the molecules in liquid state are loosely packed and has less force of attraction between the molecules, but as it is converted to solid, the force of attraction between the molecule increases and hence entropy decreases.

  • If in a reaction , less number of gaseous atoms are present in the product side , entropy will decrease , i.e. Δ°S < 0

From the question ,

( a )  NH₃(g) + 5 O₂(g) → 4 NO(g) + 6 H₂O(g)

Gaseous atoms -

Reactant - 1 + 5 = 6

Product - 4 + 6 = 10 ,

Hence ,

More number of gaseous atoms are present in the product side , So ,

entropy will increase , i.e. Δ°S > 0

( b ) CH₄(g) + 2 O₂(g) → CO₂(g) + 2 H₂O(g)

Gaseous atoms -

Reactant - 1 + 2 = 3

Product - 1 + 2 = 3 ,

Since ,

Both the side the value of gaseous atoms are , hence , Δ°S = 0 .

( c ) CaCO₃(s) → CaO(s) + CO₂(g)

Gaseous atoms -

Reactant = 0

Product - 0 + 1 = 1 ,

Since ,

Hence ,

More number of gaseous atoms are present in the product side , So ,

entropy will increase , i.e. Δ°S > 0

8 0
4 years ago
Erosion and weathering can both cause changes to the surface of Earth. Which of the following happens only because of erosion an
dangina [55]

Answer:

caves

Explanation:

BRAINLIEST

You didn't give any examples

7 0
4 years ago
Name at least two benefits of using models in science
STatiana [176]

Answer:

Viewing systems from multiple perspectives.

Discovering causes and effects using model tractability.

Improving system understanding through visual analysis.

Explanation:

Got this from google, lol. But, I put three here just in case you could get extra credit for more than two.

3 0
3 years ago
Read 2 more answers
Determine the volume in mL of 0.37 M HClO4(aq) needed to reach the half-equivalence (stoichiometric) point in the titration of 2
Dimas [21]

Answer:

14.3mL you require to reach the half-equivalence point

Explanation:

A strong acid as HClO₄ reacts with a weak base as CH₃CH₂NH₂, thus:

CH₃CH₂NH₂ + HClO₄ → CH₃CH₂NH₃⁺ + ClO₄⁻

As the reaction is 1:1, to reach the equivalence point you require to add the moles of HClO₄ equal to moles CH₃CH₂NH₂ you add originally. Also, half-equivalence point requires to add half-moles of CH₃CH₂NH₂ you add originally.

Initial moles of CH₃CH₂NH₂ are:

20.8mL = 0.0208L × (0.51mol CH₃CH₂NH₂ / 1L) =

0.0106moles CH₃CH₂NH₂

To reach the half-equivalence point you require:

0.0106moles ÷ 2 = 0.005304 moles HClO₄

As concentration of HClO₄ is 0.37M, volume you require to add 0.005304moles is:

0.005304 moles HClO₄ ₓ (1L / 0.37mol) = 0.0143L =

<h3> 14.3mL you require to reach the half-equivalence point</h3>

7 0
3 years ago
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