C) Thermal energy. Your body turns the mechanical energy into thermal energy.
Tin-120 because an atom has to have a neutral charge. If an atom has 50 electrons it must have 50 protons unless it's an ion. Add 70 to the atomic mass because it has 70 neutrons on top of 50 protons. That equals to 120. Tin has an atomic number of 50 (meaning it has 50 protons) and it has roughly an atomic mass of about 118. If the given has 70 neutrons then it's a isotope of tin.
B. White Dwarf.
<h3>Explanation</h3>
The star would eventually run out of hydrogen fuel in the core. The core would shrink and heats up. As the temperature in the core increases, some of the helium in the core will undergo the triple-alpha process to produce elements such as Be, C, and O. The triple-alpha process will heat the outer layers of the star and blow them away from the core. This process will take a long time. Meanwhile, a planetary nebula will form.
As the outer layers of gas leave the core and cool down, they become no longer visible. The only thing left is the core of the star. Consider the Chandrasekhar Limit:
Chandrasekhar Limit:
.
A star with core mass smaller than the Chandrasekhar Limit will not overcome electron degeneracy and end up as a white dwarf. Most of the outer layer of the star in question here will be blown away already. The core mass of this star will be only a fraction of its
, which is much smaller than the Chandrasekhar Limit.
As the star completes the triple alpha process, its core continues to get smaller. Eventually, atoms will get so close that electrons from two nearby atoms will almost run into each other. By Pauli Exclusion Principle, that's not going to happen. Electron degeneracy will exert a strong outward force on the core. It would balance the inward gravitational pull and prevent the star from collapsing any further. The star will not go any smaller. Still, it will gain in temperature and glow on the blue end of the spectrum. It will end up as a white dwarf.
The heat of the reaction is an extensive property: it is proportional to the quantity of the quantity that reacts.
The change in enthalpy is a measured of the heat evolved of absorbed.
When the heat is released, the change in enthalpy is negative.
The reaction of 2 moles of Na develops 368.4 kj of energy.
Calculate the number of moles of Na in 1.90 g to find the heat released when this quantity reacts.
Atomic mass of Na: 23 g/mol
#mol Na = 1.90 g / 23 g/mol = 0.0826 mol
Do the ratios: [368.4 kj/2mol ] * 0.0826 mol = 15.21 kj.
Then the answer is that 15.21 kj of heat is released (evolved)