[april.art]

Hi, I am doing some tests and I cannot understand the answer for some questions. If someone could explain would be great.

1. 6x 10v19 oxygen atoms are in:
-answer: 2.5 x 10v-2 mmoles of H2S04

2. For the reaction N2+O2-->N02 at least 0.5moles of nitrogen (IV) dioxide could be formed when reacted:
- 0.5M of N2 and 1M of O2 and 0.5M of N2 and 0.5M of O2

3. How many grams of Na2CO3x10H2O should be dissolved in water to give 100ML of 0.1M solution?
-2.86

4. For the reaction A+B-->2C the K is equal to 1. Initial concentration of A and B were 1M. At equlibrium molar concentration of C is:
-0.5M

I had chemistry 4years ago and now I want to change a career and Im preparing fo the enrance exam, i read my notes but still these questions are remained without understanding.

Thanks

[Borek]

1. 6x 10v19 oxygen atoms are in:
-answer: 2.5 x 10v-2 mmoles of H2S04

What is a mole?

How many atoms of oxygen in one molecule of sulfuric acid?

[april.art]

1mol - 6.02x10v23 atoms ions etc. still dont knw the answer. I tried!

[Borek]

How many atoms of oxygen in one molecule of sulfuric acid?