We'll go over all the formulas you need to find pH, pOH, acid concentration and base concentration. Hello everyone I'm Melissa Maribel your personal tutor and let's go over two potential test questions. In question 1, we are given the concentration of acid and asked to find the pH, pOH and base concentration to find the pH we will use the pH formula and plug in the given acid concentration. Alright, important significant figure note, pH and pOH have specific significant figure rules when you are given an acid or base concentration the amount of sig figs you have will be the amount of decimal places the pH and pOH should be rounded to, this is why we get 3.39 as our pH and note our pOH will also have two decimal places. Since we just found the pH we can use this formula and plug in pH to find pOH subtract both sides by three point three nine and our pOH is ten point six one since we just found pOH and we are now finding the concentration of base we can use this formula and plug in the pOH. Plugging this into your calculator make sure to press 2nd log and then put the exponent of negative ten point six one. Round to two sig figs since our initial acid concentration had only two sig figs. This gives us two point five times ten to the negative 11th and our units are in molarity since concentration is measured in molarity. In question two we are given the pH and asked to find our acid and base concentrations and the pOH starting with part A since we are given the pH we can use this formula and solve for that acid concentration so press 2nd log on your calculator then input the exponent of negative 8.5 and we get this as our acid concentration. Significant figure note when we're going from pH to acid concentration the number of decimal places for the pH tells you how many sig figs to round to this is why our acid concentration only has one sig fig. Part B to find our base concentration we will use this formula and plug in the acid concentration we've just found divide both sides and we will get this as our base concentration rounded to one sig fig. Part C there are two formulas we can use to find pOH in this case here's the first formula we'll plug in the base concentration to get this as our pOH the second formula we could have used instead was this one and we can plug in our pH subtract both sides by 8.5 and we would get the same value. Now here's a summary of when to use each formula when going from your acid concentration to pH use this formula. Going the opposite way from pH to acid concentration use this. Now when you're going from your base concentration to pOH use this formula. Going the opposite way from pOH to base concentration use this if you are given the pH and asked to find pOH or going from pOH to pH use this formula. Going from acid concentration to your base concentration or vice versa base concentration to acid concentration use this. If you want to cut your study time in half I created detailed notes on everything you need to know on acids and bases you can find that in the description box below and make sure to check out this other helpful video and remember stay determined you can do this!