How to calculate the number of molecules hitting a surface
Calculating the number of molecules hitting a surface each second can be very beneficial when dealing with surfaces at the microscale. We can determine whether a reaction will occur for a biosensor by whether we have enough particles accumulating at a surface or to determine what should be changed in the system to increase or decrease the interactions at a surface. Knowing the parameters that dictate the collision frequency of particles or molecules or atoms at a surface helps the designer of the system control the situation.
Things You'll Need
Manometer
Calculator
Thermometer
Periodic table of elements
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Instructions
1
Manometers measure vapor pressure.
Measure the vapor pressure using the manometer. Make sure the units are in pascals. This quantity will be equal to P.
2
Add the molecular weights of the individual atoms to calculate the overall molecular weight.
Calculate the molecular weight of the molecule of interest that will be bombarding your surface. This will be equal to the variable MW.
3
Measure the temperature using the thermometer and convert to units of Kelvin. This value will be equal to T.
4
Take the square root of the quantity (2 times 3.142 times MW times 1.381* 10^-23*T). This value will be equal to D.
5
Divide P by D. This value is the number of molecules hitting a meter-by-meter area every second.