The graph below shows the volume of hydrogen evolved against time for the reaction of a piece of solid magnesium metal with 1.00 mol dm-3 hydrochloric acid, HCl(aq). Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)

Calculate the mass of the piece of magnesium metal used.

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explanation:

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considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.