[Fmeub]

I have an exam Friday, and this is a question from an old paper, but I don’t have the memorandum and so I’m not sure whether my answer is correct.

How many mL of concentrated 70.5 % (w/w) nitric acid solution having a density of 1.42 g/cm³ is required to prepare 500.0 mL of a 0.50 M HNO₃ solution? M[HNO₃] = 63.0 g/mol.

The answer that I worked out was 15.73 mL.

If it's very incorrect, I'll go and work on it again, but if it's wrong because of significant digits, then just specify that please.

[Borek]

Seems OK.

[JGK]

I get the same Result 

[Fmeub]

Here is a question that confuses me a bit more, and I'm less confident about my answer.

A student is to prepare 1.00 L of 1.00 M H₂SO₄ by mixing 250.00 mL of 2.50 N H₂SO₄ solution (assume its density to be 1.08 g/cm³ ) with concentrated 96.5 % (w/w) sulphuric acid solution having a density of 1.84 g/cm³. How many mL of concentrated sulphuric acid is required? M[H₂SO₄] = 98.0 g/mol.

My answer is 37.94 mL.

I'm unsure about the normality. Does it in this case mean that 2.50 N H₂SO₄ is equivalent to 1.25 mol in 1 L, so in the above solution there is 0.3125 mol in the 250 mL? 

[Borek]

As for normality - it depends. Normality is different for different reactions - see

http://www.chembuddy.com/?left=concentration&right=normality

for details on the sulfuric acid.

[Fmeub]

Thanks! It is explained in a simple manner on that website. Do you find any fatal flaw in my answer?

[Borek]

Do you find any fatal flaw in my answer?

No, value seems OK once again