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Why the answr is A?

Dencology

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  1. Pre-Dental
    I don't understand what is the difference between A and C? any help. Ans. is A

    Which of the following pairs would most accurately produce a 10 Which of the following pairs of sample compounds would most accurately produce a 10% HNO3 acid?
    A. 10 g HNO3 and 90 g H2O B. 10 g HNO3 and 100 g H2O C. 10 ml HNO3 and 90 ml H2O D. 10 ml HNO3 and 100 ml H2O E. 10 g HNO3 and 100 ml H2O
     

    Contach

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      is the density of HNO3 1g/ml?
      no only the density of water is 1g/mL.. but in terms of 10% HNO3 by volume.... C is a correct answer.

      I think the question is ambiguous, as they want you to assume they are asking for 10% HNO3 by mass, as opposed to volume, which it could be.

      Then again, you can't have pure HNO3, as this wouldn't be an acid without water in it.. HNO3 would not dissociate if there weren't water molecules around... thus the 10mL of HNO3 in choice C must have some water present and is not 10mL of pure HNO3 thus cannot be exactly 10% HNO3 by volume...
       
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      doc toothache

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      1. Dentist
        I don't understand what is the difference between A and C? any help. Ans. is A
        Which of the following pairs of sample compounds would most accurately produce a 10% HNO3 acid?
        A. 10 g HNO3 and 90 g H2O B. 10 g HNO3 and 100 g H2O C. 10 ml HNO3 and 90 ml H2O D. 10 ml HNO3 and 100 ml H2O E. 10 g HNO3 and 100 ml H2O

        Then again, you can't have pure HNO3, as this wouldn't be an acid without water in it.. HNO3 would not dissociate if there weren't water molecules around... thus the 10mL of HNO3 in choice C must have some water present and is not 10mL of pure HNO3 thus cannot be exactly 10% HNO3 by volume...

        Pure nitric acid (100%) is a colorless liquid and yes it does exist. A bit confused about the need for water to make HNO3 an acid.


        Theyre asking percent by mass. The specific gravity doesnt come into play.

        It is not necessary to know the actual value of the specific gravity of HNO3. However, it does require one to understand that in all likelyhood HNO3 is going to be heavier than H2O and that a 10% HNO3 by volume would actually contain more than 10g of acid, making the wgt/wgt combination "most accurately produce a 10% HNO3 acid". The specific gravity was given to nudge the OP into understanding why the vol/vol solution would be a less accurate representation of the concentration.
         
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