# Stoichiometry help

1. Nov 18, 2006

### sweetshelly

This is the question:
How many phosphorus atoms are contained in 8.75 moles of H2P2O7? Put your answer in E-format with 1 number before and 2 numbers after the decimal place. e.g., 6.02 x 1023 would be input as 6.02E23.

the answer is : 1.05E25 (1.05 × 1025)

I really have no idea where to start. Please someone help me

2. Nov 18, 2006

### siddharth

To start off, how many atoms are there in 1 mole of phosphorus atoms?

http://www.fordhamprep.org/gcurran/sho/sho/skills/moleconex.htm [Broken]

Last edited by a moderator: May 2, 2017
3. Nov 19, 2006

### kinthos

You've been given 8.75 moles of H2P2O7, which contains 2x8.75 moles of H, 2x8.75 moles of P, and 7x8.75 moles of O. In one mole of anything (H2P2O7, P atoms, eggplants, etc), there are 6.02E23 particles.

4. Nov 19, 2006

### sweetshelly

wow thank you so much. This explanation gave me the correct answer. I really appriciate your help a lot. This is part of our exam review. If I didn't know how to solve this problem I would miss it. I can't afford not knowing something b/c we only have 20 questions total. I need an A on tomorrow test to make an A average for the semester. You're the greatest :rofl: :rofl: :rofl: :rofl: