An early finding in the history of chemistry was that a compound-say water-is co

Question

An early finding in the history of chemistry was that a compound-say water-is composed of elements in the same ratio of masses irregardless of where the compound -say water- is composed of elements in the same ratio of masses irregardless of where the compound is found. This became known as the Law of Constant Composition. Which statement is NOT consistent with this law? A) When you drink pure water (H20), you can be certain the H and O ome in a ratio of 2 g to 16 g. B) Scientists discovered a new form of carbon dioxide (CO2) having 12g of C for every 16 grams of O. 3) Scientists idenitified the has as carbon dioxide (CO2) because its ratio of C to O was 12 to 32 g.

Explanation / Answer

A) When you drink pure water (H20), you can be certain the H and O ome in a ratio of 2 g to 16 g.

Yes, this must be correct, since

1 mol f H2O --> 2 mol of H and 1 mol of O ALWAYS

note that molar mass of H = 1 g/mol

and molar mass of O = 16 g/mol

then, 2H = 2 g; 1 O = 16

ratio will be always 2:16 = 18

B) Scientists discovered a new form of carbon dioxide (CO2) having 12g of C for every 16 grams of O.

This must be FALSE, since the ratios aren't those expecte, proof:

1 mol of CO2 = 1 mol of C + 2 mol of O

molar mass of C = 12 g/mol

molar mass of O = 16 g/mol

then

C*1 = 12 g

O*2 = 32 g

ratio is 12:32 NOT 12:16

3) Scientists idenitified the has as carbon dioxide (CO2) because its ratio of C to O was 12 to 32 g.

This must be true, as stated in (B)

the ratio is

1:2

12 g of C : 16*2 = 32 g of O

12:32

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