you have a 25.2 l sample of gas at 1.25 atm and 25.0 degrees celsius. how many moles are present in this gas. for your answer, do not include units and provide your answer to three significant figures.

Explanation:

This is a direct application of the equation for ideal gases.

Where:

Solving for n:

Substituting:

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.  

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.