16 g of oxygen has same number of molecules as in
Which of the following terms are unitless?
One of the statements of Dalton's atomic theory is given below "Compounds are formed when atoms of different elements combine in a fixed ratio"
Which of the following laws is not related to this statement?
23 What will be the mass of one atom of $\mathrm{C}-12$ in grams?
The mass of a carbon-12 atom was determined by a mass spectrometer and found to be equal to $1.992648 \times 10^{-23} \mathrm{~g}$. It is known that 1 mole of $\mathrm{C}-12$ atom weighing 12 g contains $\mathrm{N}_{\mathrm{A}}$ number of atoms. Thus,
1 mole of $\mathrm{C}-12$ atoms $=12 \mathrm{~g}=6.022 \times 10^{23}$ atoms
$\Rightarrow 6.022 \times 10^{23}$ atoms of C - 12 have mass $=12 \mathrm{~g}$
$\therefore \quad 1$ atom of $\mathrm{C}-12$ will have mass $=\frac{12}{6.022 \times 10^{23}} \mathrm{~g}$
$=1.992648 \times 10^{-23} \mathrm{~g} \approx 1.99 \times 10^{-23} \mathrm{~g}$
How many significant figures should be present in the answer of the following calculations?
$$\frac{2.5 \times 1.25 \times 3.5}{2.01}$$
Least precise term 2.5 or 3.5 has two significant figures.
Hence, the answer should have two significant figures
$$\frac{2.5 \times 1.25 \times 3.5}{2.01} \approx 5.4415=5.4$$