Which of the following statements are correct? (Given : At. wt. of Ca = 40 u, Mg = 24 u, N = 14 u, H = 1 u, Na = 23 u, CI = 35.5 u)
I. 240 g of calcium and 240 g of magnesium elements have a molar ratio of 3 : 5.
II. 100 g of `N_2` contains more atoms than 100 g of `NH_3`.
III. Total number of ions in 5.85 g of sodium chloride is `1.2 xx 10^(22)`
IV. 1 gram molecule of hydrogen gas contains `12.046 xx 10^(23)` atoms of hydrogen.
V. 5.6 g of nitrogen gas occupies 3.2 L of volume at STP.

Options

A. II and III only
B. I, II and III only
C. I and IV only
D. IV and V only

Answer

C

Explanation

I: No of moles of Ca `=240/40 = 6`
No. of moles of `Mg = 240/24 = 10`
Molar ratio of Ca and Mg `=6:10 = 3:5`
11. Molar mass of `N_2 = 28 u`
Molar mass of `NH_3 = 14 + 3 xx 1 = 17 u`
No.fo atoms in 100 g `N_(2) = 100/28 xx N_(A) xx 4`
`=23.55 N_(A)` atoms
where, `N_(A) = 6.023 xx 10^(23)`
III. Molar mass of `NaCl = 23 u + 35.5 u = 58.5 u`
1 molecule of NaCl contains two ions, i.e., `Na^+` and `Cl^(-)`.
58.5 g of NaCl contains = `2 xx 6.023 xx 10^23` ions
`therefore` 5.85 g of NaCl will contain `=(2 xx 6.023 xx 10^(23))/58.5 xx 5.85` ions
`=1.2046 xx 10^(23)` ions
IV. 1 gram molecule of hydrogen gas contains `6.023 xx 10^(23)` molecules of `H_2` or `2 xx 6.023 xx 10^23` atoms of hydrogen `= 12.046 xx 10^23` atoms of hydrogen
V. 28 g of `N_2` occupies = 22.4 L of volume at STP
`therefore 5.6 g` of `N_2` will occupy `=22.4/28 xx 5.6 L = 4.48 L` of volume