A flask of gaseous C2H2 was weighed at a measured temperature and pressure. The mass of the gas was determined to be 1.5g. The flask was then flushed and filled with nitrogen at the same temperature and pressure. Find the mass of the nitrogen in the flask.

1.6g of N2 are present in the flask

Explanation:

Assuming an ideal gas, the initial moles of the gas = Moles of nitrogen because temperature, volume (Flask) and pressure are the same.

To solve this question we must find the moles of C2H2 = Moles nitrogen. Then using molar mass of nitrogen we can find its mass:

Moles C2H2 -Molar mass: 26.04g/mol- = Moles N2

1.5g * (1mol / 26.04g) = 0.0576 moles C2H2 = Moles N2

Mass N2 -Molar mass: 28g/mol-

0.0576 moles N2 * (28g / mol) =

1. 1 mole of anything contains 6.022x10^23 pieces  

d  

2. a  

3. c, number  

5. 1.24x10^24atoms / 6.022x10^23atoms/mole = 2moles h2 atoms  

6. fe2br3 mass = 2moles x mass fe + 3 moles x mass br  

molar mass = grams / number of moles = g/mole  

to find moles = g / molar mass  

to find mass = g = molar mass / moles