234 92U undergoes alpha decay. What is the atomic number of the resulting element. Express your answer numerically as an integer.

90

Explanation:

Let ʸₓA be the resulting element when ²³⁴₉₂U under goes alpha decay.

Thus, the equation is given below

²³⁴₉₂U —> ʸₓA + ⁴₂He

The atomic number x of the resulting element can be obtained as follow:

92 = x + 2

Collect like terms

92 – 2 = x

90 = x

Therefore,

x = 90

Thus, the atomic number of resulting element is 90.

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g