Question:
If number of molecules present in 9g of water is n, then number of molecules present in 44 g of carbon-di-oxide is
(A) n
(B) 2n
(C) n/2
(D) 3n
Answer:
(B) 2n
Explanation:
To find the number of molecules present, you can use Avogadro's number, which states that one mole of any substance contains approximately \( 6.022 \times 10^{23} \) molecules.
For water (\( H_2O \)), the molar mass is approximately 18 g/mol, and for carbon dioxide (\( CO_2 \)), it's approximately 44 g/mol.
So, the number of moles of water in 9g is \( \frac{9 \text{ g}}{18 \text{ g/mol}} = \frac{1}{2} \) mole.
And the number of moles of \( CO_2 \) in 44g is \( \frac{44 \text{ g}}{44 \text{ g/mol}} = 1 \) mole.
Now, since one mole of any substance contains \( 6.022 \times 10^{23} \) molecules, the number of molecules in 9g of water (\( \frac{1}{2} \) mole) is \( \frac{1}{2} \times 6.022 \times 10^{23} \).
The number of molecules in 44g of \( CO_2 \) (1 mole) is \( 1 \times 6.022 \times 10^{23} \).
Comparing the two:
\( \frac{1}{2} \times 6.022 \times 10^{23} \) (water) vs. \( 1 \times 6.022 \times 10^{23} \) (\( CO_2 \))
Since the number of molecules in 44g of carbon dioxide is double the number of molecules in 9g of water, the answer is (B) 2n.