pH chem question

[ManzRDH]

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Please explain:

9g of HCL(g) is dissolved in H2O to make 300 mL of acid solution. assuming the acid completely ionizes, what is the pH of the resulting solution?


A -log <36/(.3*9).

b -log<(36*9)/.03>

c- -log<9/(.3*36)>

d -log<.3/(9*36)>

e -log <(18*9)/(36*.3)>

 

[MSZ]

The answer is c.

To find the pH of a solution, you need to know the concentration of H+ ions. To determine the concentration, you need to find the solution's molarity which is moles per liter or moles/liter. Since you have 9g of HCL, you first need to convert that to moles. The molar mass of HCL is 36 g. Therefore, 9/36 = the number of moles of HCL. Then you need to change the volume from mL to L so 300 mL=.3 mL. All together, it looks like this 9/36*.3. Once you find the concentration of the solution, you take the - log of the molarity (or concentration) and that's your answer.

 

[ManzRDH]

Thanks for your help