There is 1 H atom: (1)(+1) = +1 The oxidation number of O is -2. There are 4 O atoms here: (4)(-2) = -8 So the oxidation state of Cl is +7.
NOTE: The maximum positive oxidation number for chlorine is +7,<span> the same as its group number (VII).</span>
Answer:

Explanation:
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In this case, given the reaction:

It means that since the coefficients preceding phosphorous and phosphorous trifluoride are 1 and 4, the correct mole ratio should be:

Because given the mass of phosphorous it is convenient to convert it to moles and then cancel it out with the moles on bottom of the mole ratio.
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Answer:
45 neutrons
Explanation:
Bromine has 35 protons and a mass number of 80. a) How many neutrons does the atom of bromine have? The mass number = protons + neutrons. Bromine has a mass number of 80 and 35 protons so 80-35 = 45 neutrons.
1) To find the change in enthalpy, determine the difference between the potential energy of the products and the potential energy of the reactants. (on this diagram, C-A) To find the activation energy, find the difference between the potential energy of the reactants and the "peak" of the curve (on this diagram, B-A). For this diagram, both the enthalpy and activation energy are positive.
2) If the reaction was exothermic, enthalpy would be negative, and the potential energy of the reactants would be greater than the potential energy of the products.