A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms
Answer:
The total energy of the photons detected in one hour is 7.04*10⁻¹¹ J
Explanation:
The energy carried by electromagnetic radiation is displaced by waves. This energy is not continuous, but is transmitted grouped into small "quanta" of energy called photons. The energy (E) carried by electromagnetic radiation can be measured in Joules (J). Frequency (ν or f) is the number of times a wave oscillates in one second and is measured in cycles / second or hertz (Hz). The frequency is directly proportional to the energy carried by a radiation, according to the equation: E = h.f, (where h is the Planck constant = 6.63 · 10⁻³⁴ J / s).
Wavelength is the minimum distance between two successive points on the wave that are in the same state of vibration. it is expressed in units of length (m). In light and other electromagnetic waves that propagate at the speed of light (c), the frequency would be equal to the speed of light (≈ 3 × 10⁸ m / s) between the wavelength :

So:

In this case, the wavelength is 3.35mm=3.35*10⁻³m and the energy per photon is:

E=5.93*10⁻²³ 
The detector is capturing 3.3*10⁸ photons per second. So, in 1 hour:

E=7.04*10⁻¹¹ 
The total energy of the photons detected in one hour is 7.04*10⁻¹¹ J
Answer: A) grinding coffee beans
Explanation:
A physical change is defined as a change in which there is alteration in shape, size etc. No new substance gets formed in these reactions.
A chemical change is defined as a change in which a change in chemical composition takes place. A new substance is formed in these reactions.
1. Grinding coffee : Only change in size takes place, thus a physical change
2. Baking a cake: the chemical reaction occurs by combination of flour with oxygen , thus a chemical change.
3.:converting water to hydrogen and oxygen: The decomposition iof water takes place, thus is a chemical change
4.Burning of coal: the chemical reaction occurs by combination of carbon with oxygen , thus a chemical change.
Answer:
In this conditions, the gaswll weight 46.74 g.
Explanation:
The idal gas law states that:
PV = nRT,
P: pressure = 740 mmHg = 0.97 atm
V: volume = 14.5 L
n: number of moles
R: gas constant =0.08205 L.atm/mol.K
T: temperature = 29°C = 302.15K

1 mol gas ___ 82 g
0.57 mol gas __ x
x = 46.74 g