Answer:
A ; 20g of water has the least number of molecules
Explanation:
Here, we want to know which of the options represent the least number of molecules;
To calculate this, we are going to first calculate the number of moles using the formula below;
Number of moles = mass/molar mass
Then from the number of moles, we can calculate the number of molecules by multiplying the number of moles by 6.02 * 10^23 molecules
Let’s proceed;
a. That will be 20/18.02 = 1.1099 moles
1.1099 * 6.02 * 10^23 = 6.68 * 10^23 molecules
b. That will be 77/16.06 = 4.8 moles
4.8 * 6.02 * 10^23 = 2.89 * 10*24 molecules
c. That will be 68/42.09 = 1.62 moles
1.62 * 6.02 * 10^23 = 9.73 * 10^23 molecules
d. That will be 100/44.02 = 2.27 moles
2.27 * 6.02 * 10^23 = 1.37 * 10^24 molecules
e. That will be = 84/20.01 = 4.2 moles
4.2 * 6.02 * 10^23 = 2.53 * 10^24 molecules
From all the values obtained, the lowest is 20g of water
