The question asks for the correct statement of the Law of Conservation of Mass, a fundamental principle in chemistry established by Antoine Lavoisier. We need to identify the option that accurately defines this law.
Correct Option: A) Mass can neither be created nor destroyed in a chemical reaction; total mass of reactants = total mass of products
This option perfectly encapsulates the Law of Conservation of Mass. It states that mass is conserved (neither created nor destroyed) and quantifies this by equating the total mass of reactants to the total mass of products. For example, if 10 grams of substance A reacts completely with 5 grams of substance B, the total mass of the products formed will be 15 grams.
This problem can be solved by applying the Law of Conservation of Mass, which states that mass is neither created nor destroyed in a chemical reaction. Therefore, the total mass of the reactants must equal the total mass of the products.
Identify the reactants and products:
State the Law of Conservation of Mass in terms of the given reaction:
\[ \text{Mass of Iron} + \text{Mass of Sulphur} = \text{Mass of Iron Sulphide} \]
Substitute the given values into the equation:
So, the equation becomes:
\[ 2.8 \text{ g} + x \text{ g} = 4.4 \text{ g} \]
Solve for \(x\) (Mass of Sulphur):
\[ x = 4.4 \text{ g} - 2.8 \text{ g} \]
\[ x = 1.6 \text{ g} \]
Thus, the mass of sulphur used is \(1.6 \text{ g}\).
B) 1.6 g is the correct mass of sulphur, calculated using the Law of Conservation of Mass.
A) 4.4 g — This is the mass of the product (iron sulphide), not the sulphur used.
C) 6.0 g — This would be the sum of 2.8 g and 4.4 g, which is incorrect as 4.4 g is the product, not a reactant.
D) 2.8 g — This is the mass of iron, one of the reactants, not the sulphur.
The question asks for the correct statement of the Law of Constant Proportions (also known as the Law of Definite Proportions), proposed by Joseph Proust. This law is fundamental in chemistry and describes the composition of chemical compounds.
B) A chemical compound always contains the same elements combined in the same fixed ratio by mass, regardless of its source or method of preparation. This statement perfectly encapsulates the Law of Constant Proportions. It emphasizes that the elemental composition by mass is constant for a specific compound, irrespective of how it was formed or where it was obtained from.
The question asks to identify the law of chemical combination proposed by John Dalton that describes the relationship between the masses of two elements forming multiple compounds. We need to recall Dalton's contributions to chemistry and the specific laws associated with him.
D) Law of Multiple Proportions. This law, formulated by John Dalton, precisely describes the phenomenon where two elements combine to form more than one compound, and the masses of one element that combine with a fixed mass of the other bear a simple whole-number ratio. For example, carbon and oxygen form carbon monoxide (CO) and carbon dioxide (CO\(_2\)). In CO, 12 parts by mass of carbon combine with 16 parts by mass of oxygen. In CO\(_2\), 12 parts by mass of carbon combine with 32 parts by mass of oxygen. The ratio of the masses of oxygen that combine with a fixed mass of carbon (12 parts) is \(16:32\), which simplifies to \(1:2\), a small whole-number ratio.
The question asks for the correct statement of Avogadro's Law. We need to recall the definition of Avogadro's Law and compare it with the given options.
Correct Option: D) Equal volumes of all gases under the same conditions of temperature and pressure contain equal numbers of molecules
The question asks to identify the scientist who first formally proposed the atomic theory of matter, stating that matter is composed of tiny, indivisible particles called atoms, while also acknowledging earlier philosophical ideas.
John Dalton (1808), though the concept was proposed philosophically much earlier by Democritus (~400 BC): John Dalton is credited with formulating the first modern atomic theory in 1808. His theory was based on quantitative observations and explained the laws of chemical combination (Law of Conservation of Mass and Law of Definite Proportions). He proposed that elements are made of atoms, which are identical in mass and properties for a given element, and different for different elements. He also stated that atoms are indivisible and indestructible, and they combine in simple whole-number ratios to form compounds. The option correctly acknowledges the philosophical precursor, Democritus, who first conceptualized "atomos" but without experimental evidence.