The half-life of Lead-210 is 22 years. If you
have 400 atoms of Lead-210, how many will
be left after 22 years (exactly one half-life)?

See explanation

Explanation:

1. The Ketone was not sown in the question but i can give you a general idea of how to calculate its molecular weight. A ketone has a general molecular formula of CnH₂nO.

The molecular weight is calculated knowing that the relative atomic mass of carbon is 12, that of hydrogen is 1 while that of oxygen is 16.

Hence from the general molecular formula, the molecular weight of any ketone is calculated from; n(12) + 2n(1) + 16. Where n represents the number of atoms of each element in the ketone.

2. Sublimation of dry ice occurs when the molecules in dry ice absorb sufficient energy in the form of heat such that they now have enough energy for some molecules to overcome the inter molecular forces acting in the solid crystal and transform directly into the vapor phase. This process is endothermic.

3.  

cyclohexane and CH2Cl2 molecules are held together by dispersion forces.

CH3CH2OCH2CH3 and  CH3CN are polar molecules held together by  dipole-dipole forces.