Question

Which of the following will have same number of molecules at STP.

A)280cm^3 of CO2 and 280cm^3 of N2O.
B)44g of CO2 and 11.2dm3 CO
C)11.2dm^3 of O2 and 32g of O2
D)28g of N2 and 5.6dm^3 of oxygen

Answer 1

Option A) 280cm³ of CO2 and 280cm³ of N2O will have the same number of molecules at STP, since equal volumes of all gases at the same temperature and pressure contain the same number of gas particles, regardless of the type of gas.

Step-by-step explanation:

The question asks which of the provided options will have the same number of molecules at STP (Standard Temperature and Pressure). According to Avogadro's hypothesis, equal volumes of all gases at the same temperature and pressure contain the same number of gas particles. Furthermore, one mole of any gas at STP occupies a volume of 22.4 liters (L) or 22,400 cm3. Thus, at STP, every 22.4 L or 22,400 cm3 of any gas will contain Avogadro's number of molecules, which is 6.022 × 1023.

To answer the question:

• Option A) 280 cm3 of CO2 and 280 cm3 of N2O will have the same number of molecules since they are both equal volumes of gases at STP.

Even though each gas may have a different molecular mass, at STP, equal volumes of different gases contain the same number of molecules. Thus, volume-volume stoichiometry can be applied to both, confirming they have the same number of molecules.