Identify the reaction that does not obey the law of conservation of mass from the provided options:

1. $2\mathrm{Mg}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2\mathrm{MgO}\left(\mathrm{s}\right)$

2. ${\mathrm{C}}_3{\mathrm{H}}_8\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

3. ${\mathrm{P}}_4\left(\mathrm{s}\right)+5{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{P}}_4{\mathrm{O}}_{10}\left(\mathrm{s}\right)$

4. ${\mathrm{CH}}_4\left(\mathrm{g}\right)+2{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{CO}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

Match the following:

Match the following physical quantities with units.

Codes:

From 440 mg of CO₂, 10²¹ molecules are removed. The moles of CO₂ remaining is: 

1. 8.34 X 10^-3

2. 0.88 x 10^-3

3. 8. 45 X 10^-2

4. 8.81 X 10³

Which of the following statements about the reaction given below is correct?

$4\mathrm{Fe}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{g}\right)$

If the density of the solution is 3.12 g ml^-1, then what will be the mass of the 1.5 ml solution in two significant figures?

The mass percent of carbon in carbon dioxide is: 

One mole of carbon atom weights 12 g, the number of atoms in it is equal to:
(Mass of carbon – 12 is $1.9926\times {10}^{-23}$ $g$)

1. $1.2\times {10}^{23}$

2. $6.022\times {10}^{22}$

3. $12\times {10}^{22}$

4. $6.022\times {10}^{23}$