<span>A device that generates an intense beam of coherent monochromatic light (or other electromagnetic radiation) by stimulated emission of photons from excited atoms or molecules. Lasers are used in drilling and cutting, alignment and guidance, and in surgery; the optical properties are exploited in holography, reading bar codes, and in recording and playing compact discs.</span>
Answer:
+60.54 kJ/mol
Explanation:
The enthalpy of formation of a compound is the sum of the enthalpies of the formation of its constituents and the bond of them. To form a compound, energy must be lost, so, they're negative.
For SF4, the enthalpy is formed by the energy of one S, two F, and 4 S-F bond (Hb):
H = - (278.8 + 4*79.0 + 4*Hb)
-775 = -(594.8 + 4Hb)
594.8 + 4Hb = 775
4Hb = 180.2
Hb = +45.05 kJ/mol
For SF6, the enthalpy is formed by the energy of one S, six F, and 6 S--F bonds (Hb):
H = -(278.8 + 6*79.0 + 6*Hb)
-1209 = -(752.8 + 6Hb)
752.8 + 6Hb = 1209
6Hb = 456.2
Hb = +76.03 kJ/mol
Thus, the energy of S--F bond must be the average of these two:
(45.05 + 76.03)/2 = +60.54 kJ/mol
Answer:
c tarnishes in air
Explanation:
After silver has been exposed to air that contains sulphur gases, discoloration would occur. there would be darkening that is caused by the reaction with gases.When any silver object tarnishes, it brings about a disfiguring of that object. Hydrogen sulphide would be needed for this to happen. silver sulphide is black and a if a thin layer should form on any surface, it ill darken it. This is what we refer to as tarnishing.
1200cm³ of gas
Explanation:
From the analogy provided in this problem,
we know that;
three tablets will produce 600cm³ of gas
This implies that;
1 tablet of the antacid will produce 
= 200cm³
If 1 tablet of the antacid produces 200cm³ of gas,
under the same condition;
6 tablets will produce = 6 x 200 = 1200cm³ of gas
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Boyle's law brainly.com/question/8928288
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A. Decomposing water requires a high activation energy.
Explanation:
In decomposing water to release hydrogen gas to make fuel cells, the process requires a very high activation energy.
2H₂O ⇆ 2H₂ + O₂
This is the overall reaction. O-H must be broken to release free hydrogen to produce hydrogen gas.
The O-H bond is a very strong force of attraction that requires a high activation energy to overcome.
- The activation energy is the energy barrier that must be overcome before a reaction takes place.
- The sun is a renewable source of energy.
- Water decomposition produces useful oxygen gas needed by all life for cellular respiration.
Learn more:
Source of energy brainly.com/question/2948717
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