Why can you be certain of the genotype of an organism that shows a recessive trait?

An organism's genetic makeup is called its genotype, and it reflects all of the alleles, or forms of the gene, that are carried by the organism. ... Recessive alleles only express their phenotype if an organism carries two identical copies of the recessive allele, meaning it is homozygous for the recessive allele.

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.