Does molecular weight of water (H2O)
= atomic weight of 2H + O
= 2(1.008) + 15.999
= 18.015g
~ 18.02g (4. sig. fig.)
is it correct?
Yes, your calculation is correct. The molecular weight of water (H2O) is determined by summing the atomic weights of its constituent atoms. In this case, the formula H2O contains two hydrogen (H) atoms and one oxygen (O) atom.
To calculate the molecular weight:
1. Look up the atomic weights of the elements. The atomic weight of hydrogen (H) is approximately 1.008, and the atomic weight of oxygen (O) is approximately 15.999.
2. Multiply the atomic weight of hydrogen by the number of hydrogen atoms in the water molecule. In this case, there are two hydrogen atoms, so the calculation is 2 * 1.008 = 2.016.
3. Add the result from step 2 to the atomic weight of oxygen. The calculation is 2.016 + 15.999 = 18.015.
4. Round the result to the appropriate number of significant figures. In this case, you rounded to 18.02 grams, which is correct for four significant figures.
So, to summarize, the molecular weight of water is indeed approximately 18.02 grams per mole.