The selection of a right career is the matter of your interest. As you have done BSc in Chemistry, then why don't you go for MSc. As you want to select from MBA or MCA(which means that you want to totally change your field), then evaluate your potential and interest in computer field and business field. Both areas are good and have good scope, therefore, it is always better to consider your interest first and then your future plans. If you love to work with computers and you want a profession related to computers then MCA is a better option. On the other hand, MBA is also a very good field only if you have business interest. Therefore, I suggest that consider your interest, then evaluate your potentials and then select the field. As long as scope and opportunities are considered then there are opportunities for both fields, if you are talented.