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Ch.17 - Acids and Bases

Chapter 17, Problem 55

Calculate the pH of each acid solution. Explain how the resulting pH values demonstrate that the pH of an acid solution should carry as many digits to the right of the decimal place as the number of significant figures in the concentration of the solution. [H3O+] = 0.044 M [H3O+] = 0.045 M [H3O+] = 0.046 M

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Hey everyone today, we're being asked to calculate the ph of acidic solution with a hydrogen ion concentration of 0.83 molar. And we have to make sure we're using the correct number of significant figures. So before finding the ph I'd like to just go ahead and identify how many significant figures we have. So our polarity in this case 0.083 molar. And using our sigfig rules, we can determine that any zero that comes before a non zero number would be insignificant. So these zeros are insignificant because there's nothing else that is defining them Until we get to the 83 here in the hundreds and thousands place. So we have two significant figures. Let's write that down too. Sig figs with that in mind. We can go ahead and start finding the ph Now recall that ph is equal to the negative log of the concentration of hydro ni um ions in solution. And we already have that value. It's a negative log 0.083 Moller. I need three moller Which gives us a value of one point. Let's write that 1.08 one, which will Round out to 1.08, giving us again two significant figures. Thus the ph of an acidic solution with an H 30 plus concentration of 0.83 molar Is 1.08. It is extremely acidic. I hope this helps. And I look forward to seeing you in the next one