What do you use a pen for

writing. a good pen of the type and point size that's most comfortable for you. Generally I find that fine-point pens are the best for taking notes. You can write smaller and get more on a page. If your handwriting tends to be small, you'll probably prefer a fine point.

step-by-step explanation: a reaction is first order. if the initial reactant concentration is 0.0200 m, and 25.0 days later the concentration is 6.25 x 10-4 m, then its half-life is: