molality question

[Jia7]

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the answer is B. The way i calculated - converted 14 grams of NaF into moles (14/(23+19)) and divided that by kg of H2O (400x10^-6). i got 825mol/kg as the answer. Have i converted mg to kg incorrectly or am i missing something here?

thanks for your help!

 

[UndergradGuy7]

What you did is right. Answer key is wrong. The only way you would get their answer is if the mass of water was 400 g.