Calculate 3OH-4 for each of the following solutions, and indicate whether the solution is acidic, basic, or neutral: (c) a solution in which 3H+4 is 1000 times greater than 3OH-4.

Video transcript

Hello everyone. So in this video we're calculating for the concentration of our hydroxide ions as well as determining if the solution is going to be acidic, basic or neutral. So as a reference we're gonna go ahead and just use pure water and to be more specific we're gonna use pure water at room temperature. And that standard uh temperature is going to be at 25°C. Alright so at some pure water at room temperature the KW value is equal to 1.0 times 10 to the -14. So the concentration of R. H plus ions is actually equal to the concentration of O. H minus ions which is equal to 1. times 10 to the negative seven. How we get that is because we know that the K. W. Is equal to the H plus ions multiplied by the concentration of R. O. H ions. So divide by two. We will get this value here. So what we can take away from this is that if our concentration of hydroxide ions is going to be greater than 1.0 times 10 to the negative seven moller. We can say that this solution is going to be basic. If we have that the concentration of our hydroxide ions to be less than 1.0 times 10 to the negative seven moller. And this is gonna be acidic. Alright just scrolling down here to give us a little bit more space. Alright so we can say that the concentration of the hydra or the h plus ions is equal to The concentration over OH ions over 5000. And plugging that into our KW equation because we said that the H plus is equal to the concentration of R O. H. We have to of the concentration of our hydroxide multiplied together all over 5000 to go ahead and simplify this. We can say that the K. W is equal to the concentration of our hydroxide to the power of two over 5000. Now scrolling down again to give us more space to do our work. We are solving here for the concentration of our hydroxide ions. So we get 5000 times RKW value. What I just did here is to multiply both sides by 5000 to go ahead and cancel out this denominator here. Then going head to square root to isolate that concentration of hydroxide, we'll get The Square Root of 5000 times RKW. Value. Now we have a value for K. W. So let's go ahead and substitute that in. So the concentration of our hydroxide is equal to the square root of 5000 multiplied power Kw value of 1.0 times 10 to the negative 14. Now putting that into my calculator, I see that I get a value of 7. times 10 to the -6 moller. And as our reference point we want to see if that concentration of hydroxide was going to be greater than or equal to or greater than or less than The value of 1.0 times 10 to the -7 moller. We see that the calculated concentration of our hydroxide is going to be greater than this reference value. Therefore we can say so. Therefore we can say that our solution is going to be basic. So this is one of our final answers. And we also solve for the concentration of hydroxide ions. That was again 7.7 times 10 to the negative six molar. And this right here is going to be my final answer for this problem. Thank you all so much for watching.