First and second ionisation energies of ...

First and second ionisation energies of magnesium are 7.646 and 15.035 eV respectively. The amount of energy in kJ needed to convert all the atoms of magnesium into `Mg^(2+)` ions present in 12 mg of magnesium vapours is: 1.1, 1.5, 2, 0.5

1.1

1.5

0.5

Text Solution

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The correct Answer is:

Total energy needed to convert one Mg atom into.
`Mg^(2+)(g) ` ion ` = IE_1 + IE_n = 22.681 eV =2188 kJ "mol"^(-1)`
12 mg of Mg ` = 0.5 xx 10^(-3) ` mole

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Ionization enthalpy of lithium is 520 kJ mol^(-1) . How much enthalpy in jọules must be needed to convert all atoms of Li to Li^+ ions present in 7 mg of Li vapours. 74.3 kJ , 520 xx 6.023 xx 10^(-17)J , 520 J , 780 J

74.3 kJ'

520 xx 6.023 xx 10^(-17)J'

520 J'

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Calculate the energy needed to convert three moles of sodium atoms in the gaseous state to sodium ions, The ionization energy of sodium is 495 kJ mol^(-1)

1485 kJ

495 kJ

148.5 kJ

None

The K shell ionisation energies for cobalt, copper and molybdenum are 7.8, 9.0 and 20.1 keV respectively. If an X-ray tube operates at 15 kV with any of the above metals as targets, then:

characteristic X-rays of K series will be emitted only from cobalt

characteristic X-rays of K series will eb emitted only from copper and cobalt

characteristic X-rays of K-series will be emitted from cobalt, copper and molybdenum

the shortest wavelength of continuous X-rays emitted is the same for the three metals.