Avogadro's Number or Avogadro's Constant to the number of particles that constitute a substance (usually atoms or molecules) and that can be found in the amount of one mole of said substance. Its value is 6.023 * 10²³ particles per mole. Avogadro's number represents a quantity without an associated physical dimension, so it is considered a pure number that allows describing a physical characteristic without dimension or explicit unit of expression. The Avogadro number applies to any substance.
Then a rule of three applies as follows: if 1 mole has 6,023 * 10²³ atoms, 2 moles how many atoms will it contain?
number of atoms=1.2046*10²⁴ atoms
This number is already represented in scientific notation.
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Thermal equilibrium is the state in which two bodies come into mechanical contact, equalize their temperatures, due to the irradiation of one towards the other until reaching an energy balance. The thermal equilibrium point is reached when the kinetic energy that is shared between two bodies is distributed throughout the system, in other words, both bodies start to function as a single thermodynamic system, with the same internal energy and temperature
Answer: Option (b) is the correct answer.
It is known that in solids, particles are placed closer to each other due to strong forces of attraction between them. Due to this solids occupy a fixed shape an volume.
On the other hand, molecules of a liquid are held by less strong forces as compared to solids. Therefore, molecules of a liquid are able to slide past each other.
Hence, when in liquid phase particles bond together it it changes into solid phase.
Thus, we can conclude that the phase change that occurs when the attraction between liquid particles becomes a significant factor and the particles bond together is freezing.
Answer : Option C) Oxygen in air reacts with iron content in rocks, causing them to change colour.
Explanation : Chemical weathering is a process in which the disintegration of any materials takes place due to chemical reactions mainly with water and substances dissolved in it rather than by any mechanical processes.
Here, in the given options namely;
A) Freezing water widens the cracks in rocks is a physical process where the water clogged inside the cracks of rocks gets expanded on freezing at lower temperatures. No chemical change is observed in this process.
B) Plant roots force their way into cracks in rocks and break them this is also a physical process where the plant roots search for water and nutrients into the crack of rocks and eventually breaks them. Here, no chemical changes are seen.
C) Oxygen in air reacts with iron content in rocks, causing them to change color this is completely a chemical change that is occurring; as we can see that the color of rocks are changing because of a chemical reaction of oxygen in the air and the iron content in the rocks. There is also disintegration of rock which is observed in this process. So, this can be termed as chemical weathering.
D) Strong winds peel soft rock away, leaving harder rock behind it is completely a physical process where the strong winds physically peel away the soft rock and leaves behind harder rocks. No chemical change is seen or occurs.
Hence, the correct answer is Option C) which gives complete satisfactory changes to be termed as chemical weathering.
Percent composition can be solve by:
( mass desired component)/ mass sample * 100
% Nitrogen of the sample NiO can be solved:
%Ni = ( 33.1 g Ni / 41.9 g NiO) x 100
%Ni = 79% Ni
%O = ( 8.8 g O / 41.9 g NiO) x 100
%O = 21 % O
ni is 79% and o is 21%