D should be the correct answer. isotopes are atoms that have the same atomic number (number of protons) but different atomic masses (number of protons and neutrons). isotopes also have the same number of electrons since atoms need to have equal numbers of protons and electrons to not be considered ions. Since the number of protons determines the chemical properties of the atom, we can say that all isotopes have the same chemical properties due to the fact that all isotopes have the same atomic number.
I hope this helps. Let me know in the comments if anything is unclear.
Answer:
<em><u>The compound hydrogen chloride has the chemical formula HCl and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride gas and hydrochloric acid are important in technology and industry. Hydrochloric acid, the aqueous solution of hydrogen chloride, is also commonly given the formula HCl.</u></em>
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Atomic weights are weighted averages calculated by multiplying the relative abundance of each isotope by its atomic mass and then summing up all the products.
Answer:
The total enthalpy of the reaction has negative value which mean that the heat is lost during the chemical reaction into surroundings.
Explanation:
Exothermic reactions are defined as the reactions in which energy of reactants is more than the energy of the products. In these reactions, energy is released by the system.
The total enthalpy of the reaction 
comes out to be negative.
Endothermic reactions are defined as the reactions in which energy of products is more than the energy of the reactants. In these reactions, energy is absorbed by the system.
The total enthalpy of the reaction comes out to be positive.
,ΔH= -1235.7 kJ/mol
The total enthalpy of the reaction has negative value which mean that the heat is lost during the chemical reaction into surroundings.
