I really need someone to explain how to find the average atomic mass. the gizmos was really confusing because they also had weighted mass.

Option C. 52.057

Explanation:

The following data were obtained from the question:

Isotope >> Mass number > Percentage

A (Cr-50) > 50 >>>>>>>>>> 4.3

B (Cr-52) > 52 >>>>>>>>>> 83.8

C (Cr-53) > 53 >>>>>>>>>> 9.5

D (Cr-54) > 54 >>>>>>>>>> 2.4

Average atomic mass =?

The average atomic mass of chromium, Cr can be obtained as follow:

Average atomic mass = [(Mass of A × A%) /100] + [(Mass of B × B%) /100] + [(Mass of C × C%) /100] + [(Mass of D × D%) /100]

Atomic mass of Cr = [50×4.3)/100] + [52×83.8)/100] + [53×9.5)/100] + [54×2.4)/100]

= 2.15 + 43.576 + 5.035 + 1.296

Atomic mass of Cr = 52.057

Therefore, the atomic mass of chromium, Cr is 52.057

answer: the value of enthalpy change will be -152.80 kj.

solution:

pressure = 1atm , temperature = = 298 k

given that pressure and temperature are same in both gases , the number of moles of both gases can be determined by the ideal gas equation.

according to reaction 3 moles no are reacting with 1 mol of ,then 0.49 mol of no will react with moles of ozone that is 0.16 moles of ozone. since, no is limiting reagent and is an excessive reagent.

enthalpy change for the reaction between the given volumes of the gases is :