<p>alright.. guys, i know you probably think i'm stupid.. but i have become so dependent on the calculator for math that i cannot do simple decimal multiplication/division and logs in my head..
i am very worried for the math parts in the chem sat II.. even though the prolems are very simple.. i am afraid i will make careless errors..</p>
<p>and hints/tips for me?</p>
<p>For percent mass, assume there are a 100 grams of that substance.</p>
<p>Just round off numbers / change them into nice fractions.</p>
<p>For pH/pOH, keep in mind that they are defined as -log[H+], -log[OH-]. Both of these are in base 10. Know your logarithm rules.</p>
<p>If [H+] = 1e-7M, then -log(1e-7) = -(-7)log(1e0) = 7
"Log" is a function. Raising it to the power of its base undoes the function. For ex: 10^(log(5)) = 5</p>
<p>"en" = 10^n</p>
<p>I hope this helped.</p>