Uranium-238 undergoes radioactive decay according to the incomplete below. 238 92
U= 4
2 He + X.
What is the decay product represented by X?

The decay product represented by X : Thorium (Th) : ²³⁴₉₀Th

Given

Decay reaction

²³⁸₉₂U ⇒ ⁴₂He + X

Required

The decay product

Solution

Radioactivity is the process of unstable isotopes to stable isotopes by decay, by emitting certain particles,  

In a decay reaction, the sum of the mass number and atomic number of the elements in the reactants and products must be the same

So the mass number of the element X = 238 - 4 = 234

Atomic number of the element X = 92 - 2 = 90

If we look at the periodic system, then the element with atomic number 90 is Thorium (Th)

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"