Rust forms when iron metal reacts with oxygen gas. Which chemical reaction best supports the law of conservation of mass?
A. Fe + O2 --> Fe2O3
B. 2Fe + O2 --> 2Fe2O3
C. 3Fe + 202 --> Fe2O3
D. 4Fe + 302 --> 2Fe2O3

D. 4Fe + 302 --> 2Fe2O3

Explanation:

The equation that bests supports the law of conservation of mass is the choice D;

       4Fe  +   3O₂  →   2Fe₂O₃

Based on the law of conservation of mass, the number of atoms on both sides of the expression must be the same. Only the fourth choice proves this law;

           4Fe  +   3O₂  →   2Fe₂O₃

                                                Number of atoms

    Elements              Left hand side                            Right hand side

        Fe                                4                                                     4

        O                                 6                                                      6

We can see that both side of the expression have the same number of atoms and the equation is balanced.  

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answer : (a) volume of the gas = 8.67 ×   l

                (b) second virial coefficient b = -1.21226 l/mole

solution :   given,     t = 300k

                                p = 20atm

                                z = 0.86

                                n = 8.2 mmoles = 8.2 × moles

                                r =   0.082 l atm/k/mol

        find,     (a) volume of gas   and (b) second virial coefficient b at 300k.

formula used :            

                          and            

(a)            

                    = \times 0.082\times 300}{20}[/tex]

                    = 8.67 ×   l

(b)      

                    = (0.00867-1) × 8.659

                    = - 8.5839 l/mole