8. how many molecules are there in a 42.3 g sample of water, h₂o?
8. how many molecules are there in a 42.3 g sample of water, h₂o?
Answer
Explanation:
Step1: Calculate molar mass of water
The molar mass of H₂O: H has an atomic mass of approximately 1 g/mol and O has an atomic mass of approximately 16 g/mol. So, (M = 2\times1+16= 18\ g/mol).
Step2: Calculate number of moles
Use the formula (n=\frac{m}{M}), where (m = 42.3\ g) and (M = 18\ g/mol). So, (n=\frac{42.3}{18}=2.35\ mol).
Step3: Calculate number of molecules
Use Avogadro's number (N_A = 6.022\times10^{23}\ molecules/mol). The number of molecules (N=n\times N_A). So, (N = 2.35\times6.022\times10^{23}=1.41517\times10^{24}\ molecules).
Answer:
(1.42\times 10^{24}\ molecules) (rounded to three - significant figures)