0.500 MOL from HNO3 in 200 cc solution.

The book says that the answer is 157.5. I have no idea how to get this.

I have a feeling this is ridiculously easy, but I can work it out.

The first question was identical, but for 2mol of NaOH in 4 dm 3-solution. I have 20 g dm-3 which says the book is correct, and I worked it out by doing (23 + 16 + 1) divided by 2.

That is my work right?

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