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3 years ago

Which part of a star does the star’s energy come from?

Chemistry

2 answers:

kolezko [41]3 years ago

5 0

Answer:

its nuclear fusion

Explanation:

Paraphin [41]3 years ago

4 0

Answer:

For most of its active life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. At the end of a star's lifetime, its core becomes a stellar remnant : a white dwarf , a neutron star , or, if it is sufficiently massive, a black hole .

Explanation:

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How many miles can a commercial jetliner flying at 253 meters per second travel in 6.0 hours

Goryan [66]

1 mile = 1609.344 meters
1 hour = 3600 seconds 345.48 miles per hour x 1609.344
meters/mile x 1hour/3600seconds = 154.44 meter per second~~ANSWERR

6 0

4 years ago

What causes a gas to exert pressure when confined in a container

Juli2301 [7.4K]

The molecules in gas are always trying to expand

5 0

3 years ago

Which of the following has the lowest Ka?a. carbonic acid b. dihydrogen phosphate c. phosphoric acid d. bicarbonate

Naya [18.7K]

Explanation:

A compound or molecule which will have least dissociation and that is not able to given hydrogen ion easily upon dissociation will also have a low value of $K_{a}$ .

Dissociation of the given compounds or species will be as follows.

$H_{2}CO_{3} \rightleftharpoons H^{+} + HCO^{-}_{3}$

$H_{2}PO^{-}_{4} \rightleftharpoons H^{+} + HPO^{-}_{4}$

$H_{3}PO_{4} \rightleftharpoons H_{+} + H_{2}PO^{-}_{4}$

As, chemical formula of bicarbonate is $HCO^{-}_{3}$ and due to the presence of a negative charge it is difficult to lose a positively charged hydrogen ion. This is because oppositely charged ions will be bonded by strong force of attraction.

Hence, it will not easily lose a hydrogen ion due to which bicarbonate has the lowest $K_{a}$ .

Thus, we can conclude that out of the given species bicarbonate has the lowest $K_{a}$ .

7 0

3 years ago

The standard free energy of activation of a reaction A is 81.9 kJ mol–1 (19.6 kcal mol–1) at 298 K. Reaction B is one million ti

klasskru [66]

Answer:

54.9 kJ/mol

Explanation:

The relation between the activation energy (Ea) and the rate constant (k) is given by the Arrhenius equation.

$k=A.e^{-Ea/RT}$

where,

A is a collision factor

R is the ideal gas constant

T is the absolute temperature

Reaction B is one million times faster than reaction A at the same temperature. So $k_{B}=10^{6} k_{A}$ .

Then,

$k_{B}=10^{6} k_{A}\\A.e^{-Ea_{B}/RT}=10^{6}A.e^{-Ea_{A}/RT}\\e^{-Ea_{B}/RT}=10^{6}e^{-Ea_{A}/RT}\\ln(e^{-Ea_{B}/RT})=ln(10^{6}e^{-Ea_{A}/RT})\\\frac{-Ea_{B}}{RT} =ln10^{6} -\frac{Ea_{A}}{RT} \\Ea_{B}=(ln10^{6} -\frac{Ea_{A}}{RT}).(-RT)=(ln10^{6}-\frac{89.1kJ/mol}{(8.314\times 10^{-3} kJ/mol.K).298K} ).(-8.314\times 10^{-3} \frac{kJ}{mol.K}.298K )=54.9kJ/mol$

8 0

3 years ago

Which element would have properties characteristic of both a metal and a nonmetal

PolarNik [594]

Answer:

Examples: Si, B, Ge, Sb, Ga

Explanation:

The majority of elements in the periodic table are classified as either a metal (a species that can lose electrons to become a cation) or a non-metal (a species that can gain electrons to become an anion).

However, there are several atoms which are considered to be metalloids. Metalloids are elements which possess properties that resemble both metals and non-metals. Examples of metalloids would be: silicon (Si), boron (B), germanium (Ge), antimony (Sb), gallium (Ga).

Since metalloids have properties of both metals and non-metals, they are widely used in semiconductors, as they might both donate and accept electrons in their shells.

7 0

4 years ago