Design and perform an experiment to show and compare that water always contains hydrogen and oxygen in the same ratio, regardless of its source.
To demonstrate that water always contains hydrogen and oxygen in the same ratio regardless of its source, we can perform an experiment based on the Law of Constant Proportions.
First, collect water samples from different sources such as a river, a borewell, and the ocean. Purify these samples completely to remove any dissolved salts or impurities, ensuring we only analyse the pure compound.
Next, take exactly 9 g of each purified water sample and decompose it using electrolysis. Collect the hydrogen and oxygen gases produced separately and carefully measure their masses for each of the different samples.
Upon measuring the products, it is consistently observed that the decomposition of 9 g of purified water from any source always yields exactly 1 g of hydrogen and 8 g of oxygen.
This proves that elements in a compound combine in a fixed ratio by mass. The mass ratio of hydrogen to oxygen in water is always 1:8, irrespective of whether the water came from a river, borewell, or ocean, thus verifying the Law of Constant Proportions.
Explanation
The textbook context introduces the Law of Constant Proportions, which states that elements in a compound have definite proportions by mass irrespective of its source. It specifically uses water as an example, noting that purified water from rivers, borewells, or oceans always contains hydrogen and oxygen in a mass ratio of 1:8. The experiment design directly applies this concept by having the student purify water from various sources, decompose a 9 g sample, and measure the resulting 1 g of hydrogen and 8 g of oxygen to prove the constant 1:8 ratio.
Solution Steps
Step 1: Collect water samples from different sources (river, borewell, ocean) and purify them.
Step 2: Take exactly 9 g of each purified water sample.
Step 3: Decompose each 9 g sample and measure the mass of hydrogen and oxygen obtained.
Step 4: Observe that 1 g of hydrogen and 8 g of oxygen are always obtained from 9 g of water.
Step 5: Conclude that water always contains hydrogen and oxygen in a fixed mass ratio of 1:8, verifying the Law of Constant Proportions.