How many molecules of nitrogen dioxide gas (NO2) are present in 15 liters of the gas at STP?

4.031×

Explanation:

You first need to calculate the number moles of NO2.  To do this use PV=nRT

STP stands for standard temperature and pressure which is 0 degrees C and 1 atm.

due to that:

P = 1 atm

V = 15 L

R = 0.08206 L*atm/mol*K

T = 273 K

n = unknown moles

solve for n to make the equation n=PV/RT

n=(1atm*15L)/(0.08206 Latm/molK*273K)

n=0.6696 mol of NO2

Then to find the number of molecules we use Avogadro's number which tells us the number of molecules per mol of a molecule or atom.

Avogadro's number is  6.02x10^23 molecules/mol

number of molecules = 0.6696mol × 6.02x10^23 molecules/mol

number of molecules = 4.031×10^23 molecules of NO2

Let me know if anything is not clear or if you get something else in the comments so that we can work it out.

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.