- In chemistry, the law of constant composition or definite proportion also known as the Proust's law, or law of constant composition states that a given chemical compound always contains its component elements in fixed mass ratio and independent on its source and method of preparation.
Question
:The compound, carbon monoxide, CO, contains 49.2% carbon. Following the law of constant composition, how much oxygen needs to combine with carbon to form 10 grams of carbon monoxide?
GIVEN
The carbon monoxide, CO has a 49.2 per cent carbon, therefore the per cent oxygen is equal to 50.8 carbon. So, the carbon to oxygen ratio in carbon monoxide is around 0.9685.
REQUIRED
Amount oxygen needs to combine with carbon to form 10 grams of carbon monoxide?
SOLUTION AND ANSWER
Ten grams of carbon monoxide has also 49.2 per cent carbon, following the law of constant composition. Therefore, 49.2 percent multiplied by 10 grams is 4.92 grams of carbon. So, 10 grams less than 4.92 grams of carbon will yield 5.08 grams of oxygen.
Therefore, 5.08 grams of oxygen is needed to combine with carbon to form 10 grams of carbon monoxide.
Checking the ratio which is equal to 0.9685 = 4.92/5.08?
YES, it is equal!
