Which of the following corresponds to an alpha particle? A. A helium nucleus, with an atomic number of 1 and an atomic
mass of 2
O B. A hydrogen nucleus, with an atomic number of 1 and an atomic
mass of 1
C. A helium nucleus, with an atomic number of 2 and an atomic
mass of 2
D. A helium nucleus, with an atomic number of 2 and an atomic mass
of 4

Atomic number=No. of protons=No. of electrons in ground state(unchanged atom)

Atomic number=13=No. of protons

Atomic mass=no. of protons+no. of neutrons=13+14=27

For isotope no. of proton=13(same atomic number but different mass number are isotopes)

no. of electrons=13

no. of neutrons=14+2=16

Explanation:

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answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.