Please help, I'm taking my final exam its do soon!!
Which of the following illustrates the conservation of matter?
A. SnO2 + H2 --> Sn + 2 H2O
B. 2 C + O2 --> CO2
C. KOH + HBr --> KBr + H2O
D. 6 Cs + N2 --> 6 Cs3N

Option C. KOH + HBr --> KBr + H2O

Explanation:

The law of conservation of matter states that matter can neither be created nor destroyed during a chemical reaction but changes from one form to another.

An unbalanced equation indicates that matter has be created nor destroyed, while balanced equation indicates that the matter were not created not destroyed but only changes to other forms.

From the question above, only option C is balanced.

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms