most events like the rising and setting of the Sun were used a natural measurement of time until recently.
Solar time, which is based on the motion of the Sun, is not the only way of measuring time, however. One might keep track of the regular appearance of the full Moon. That event occurs once about every 29.5 solar days. The time between appearances of new moons, then, could be used to define a month.
One also can use the position of the stars for measuring time. The system is the same as that used for the Sun, since the Sun itself is a star. All other stars also rise and set on a regular basis.
Although any one of these systems is a satisfactory method for measuring some unit of time, such as a day or a month, the systems may conflict with each other. It is not possible, for example, to fit 365 solar days into 12 or 13 lunar months exactly. This problem creates the need for leap years
Read more: http://www.scienceclarified.com/Ti-Vi/Time.html#ixzz5e1E705sr
I abbreviated most of it but there is a ton more at this link if you still need more.
This problem is providing the chemical reaction whereby barium nitride reacts with water to produce barium hydroxide and ammonia, so the number of moles of barium nitride are required in order to produce 8.3 moles of ammonia. It asks for us to evaluate the student's setup, so we conclude the answer is C. "1 mol of NH3 should be replaced with 2 mol of NH3", according to:
<h3>Mole ratios:</h3>
In chemistry, stoichiometric calculations are used to figure out the moles or mass of a substance, given information about another one in the reaction. In this case, for the given chemical equation:
We evidence a 1:2 mole ratio of barium nitride to ammonia, for that reason, the student's setup:
Is incorrect, because the ammonia must be accompanied by a 2 rather than the 1 it is given there:
Thereby, the correct answer is C. "1 mol of NH3 should be replaced with 2 mol of NH3"
Learn more about mole ratios: brainly.com/question/15288923
C ! ..........................
<h3>
Answer:</h3>
4.227 × 10^-19 Joules
<h3>
Explanation:</h3>
Energy of a photon of light is calculated by the formula;
E = hf, where h is the plank's constant, 6.626 × 10^-34 J-s and f is the frequency.
But, f = c/λ
Where, c is the speed of light (2.998 × 10⁸ m/s), and λ is the wavelength.
Given the wavelength is 470 nm or 4.7 × 10^-7 m
Therefore;
E = hc/λ
= (6.626 × 10^-34 J-s × 2.998 × 10^8 m/s) ÷ 4.7 × 10^-7 m
= 4.227 × 10^-19 Joules
Therefore, the energy of a photon with 470 nm is 4.227 × 10^-19 Joules
