Gen Chem Question

[shoombol tallah]

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Can anyone help me with this question, I cant seem to figure it out

HOW MANY ml OF WATER MUST BE ADDED TO 65ml OF A 5.5 m SOLUTION OF NaOH IN ORDER TO PREPARE A 1.2-M NaOH SOLUTION?


answer is 235ml

 

[Clubby]

MV=MV Come on man.

 

[shoombol tallah]

lol its not that simple i wish it was . it gives you 5.5 molality and asks for 1.2 Molar.

If you do M1V1=M2V2 you get something like 297.92ml. There is a conversion in there somewhere.

 

[fancymylotus]

Can anyone help me with this question, I cant seem to figure it out

HOW MANY ml OF WATER MUST BE ADDED TO 65ml OF A 5.5 m SOLUTION OF NaOH IN ORDER TO PREPARE A 1.2-M NaOH SOLUTION?


answer is 235ml

5.5 m= molality

1.2 M= molarity

😕 or is that your typo.

 

[shoombol tallah]

no typo on my part. thats the part that gets me because the original question has 5.5 m = 5.5 molality and 1.2 M = 1.2 molarity so they want you to go from molality (m) to molarity (M)

 

[TheWiredNerv]

Can anyone help me with this question, I cant seem to figure it out

HOW MANY ml OF WATER MUST BE ADDED TO 65ml OF A 5.5 m SOLUTION OF NaOH IN ORDER TO PREPARE A 1.2-M NaOH SOLUTION?


answer is 235ml

Recall 1 kg water = 1L m moles NaOH / 1 Kg = moles NaOH / 1L = 5.5
(.065 L )(5.5) = 0.36 moles NaOH
Now you have added 65 mL so far. Let X = amount of water needed to dilute NaOH to 1.2 M

M = moles / L ( 0.36 moles NaOH / (0.065 + x) L ) = 1.2 M NaOH
0.078 + 1.2X = 0.35 1.2x = 0.282 x = 0.282 / 1.2 = 0.235
0.235 L = 235 mL

There ya go.