So, I asked my friend to get me a chocolate cake mix, but she accidentlt got me a brownie mix instead (Betty Crocker Brownie mix). I wanted to make a chocolate cake for tomorrow's Super Bowl. However, if there's no hope then I'll just make the brownies.  I can't turn them into cupcakes because I have no cupcake molds. I just have a rectangular pan. I also don't have baking powder.   So the insturctions on the box say to add 1/4 cup of water, 1/4 vegetable oil, and 1 egg.  I've seen some sites that says to add one more egg. Would that really help? Has anyone converted a brownie mix into a cake?   
My answer would be to add more cake flour if you have it, but AP flour will do it too, then add an additional teaspoon of baking soda.  The flour will lighten the mix so it's not so dense chocolate/cocoa, and the additional baking soda will help it rise more than a brownie.  An additional egg won't hurt, and it will certainly help the stickier of the cake, but I don't know if it's necessary. 