Question

It has been determined experimentally that two elements, \(\mathrm{A}\) and \(B\) react chemically to produce a compound or compounds. Experimental data obtained on combining proportions of the elements are: $$ \begin{array}{|l|l|l|l|} \hline & \text { Grams of A } & \text { Grams of B } & \begin{array}{l} \text { Grams of } \\ \text { compound } \end{array} \\ \hline \text { Experiment 1 } & 06.08 & 04.00 & 10.08 \\ \hline \text { Experiment 2 } & 18.24 & 12.00 & 30.24 \\ \hline \text { Experiment 3 } & 3.04 & 2.00 & 5.04 \\ \hline \end{array} $$ (a)Which two laws of chemical change are illustrated by the above data? (b) If \(80 \mathrm{~g}\) of element: \(\mathrm{B}\) combines with \(355 \mathrm{~g}\) of a third element \(\mathrm{C}\), what weight of \(\mathrm{A}\) will combine with \(71 \mathrm{~g}\) of element \(\mathrm{C} ?\) (c) If element \(\mathrm{B}\) is oxygen, what is the equivalent weight of element \(\mathrm{C}\) ?

Short answer

The given experimental data illustrates the Law of Conservation of Mass and the Law of Definite Proportions. To calculate the weight of element A that will combine with 71g of element C, we first determine the ratios A:B and B:C and multiply them to obtain the ratio A:C. Using this ratio, the weight of A required is 24.25g. If element B is oxygen, the equivalent weight of element C is 71g/mol.

Step-by-step solution

Identification of Laws Demonstrated by the Data

The experimental data provides information about the weights of elements A and B in three experiments, and the weight of the compound formed in each case. From the data, it can be noticed that the combined weight of A and B equals the weight of the compound formed, in accordance with the law of conservation of mass. Furthermore, it can also be observed that the ratio of the weights of A and B is consistent across the experiments, demonstrating the law of definite proportions.

Calculation of Weight of A needed to combine with C

Here, two ratios are of interest: A to B (from the experiments) and B to C (from the given weight data). Basing on the experiments data, the ratio A:B can be obtained as 1.52 (06.08/04.00). The ratio B:C is 0.2256 (80/355). Multiplying these ratios would give the ratio A:C as 0.343 (1.52*0.2256 = 0.343). Thus, for 71g of C, the weight of A required would be 24.25g (0.343*71).

Calculation of Equivalent Weight of C if B is Oyxgen

Given that B is oxygen and the weight of B that combines with C is 80g, and considering the atomic weight of oxygen is 16g/mol, the moles of oxygen would be 5 (80/16). The weight of C that combines with oxygen is 355g, thus the equivalent weight of C (which is weight of C divided by the moles of oxygen) would be 71g/mol (355/5).

Key concepts

Law of Conservation of Mass

The law of conservation of mass states that mass in an isolated system is neither created nor destroyed, but merely rearranges its components. This means that in any chemical reaction, the mass of the reactants is equal to the mass of the products.
In the experiments provided, we can observe this principle in action. For instance, when element A and element B are combined, the total mass of both elements equals the mass of the resulting compound. This is evident as each experiment shows the sum of the grams of A and B equating to the grams of the compound.
Understanding this concept is essential to predict product formation, as it implies that all elements are accounted for in a reaction. Moreover, it is a foundational principle for all chemical reactions and helps ensure accuracy in experimental chemistry.

Law of Definite Proportions

The law of definite proportions, also known as Proust's law, asserts that a chemical compound will always contain the same proportion of elements by mass, regardless of the amount or source of the compound. This means that the ratio of elements in a compound is constant.
In the given data, the ratio of the mass of element A to element B is consistent across all experiments, calculated as 1.52 (from combining 06.08 grams of A with 04.00 grams of B). This consistent ratio across various amounts demonstrates this law, confirming that no matter how much or how little of a compound is made, the ratio of its elements remains unchanged. This consistency is crucial for scientists to understand compound formation and convert reactant masses to product masses accurately.

Chemical Reactions

A chemical reaction involves the transformation of reactants into products through the breaking and forming of bonds. In this process, elements combine in specific ways defined by their chemical properties.
When A and B react to form a specific compound, it showcases how new substances are generated from pre-existing substances, adhering to the aforementioned chemical laws. It's important to note that these reactions often require precise conditions including the correct temperature and pressure.
Learning about chemical reactions helps students understand how substances interact and change, which is vital for fields ranging from cooking to biotechnology.

Element Combination

Element combination refers to how different elements join together to form compounds. Each element has unique properties that define how it will interact with other elements.
In the experiments, elements A and B join to form new compounds, showcasing their tendency to combine in fixed ratios according to their chemical nature. This property of combining in certain ratios is driven by their valency and electronegativity.
Recognizing how elements combine is essential for predicting the types of compounds they can form when mixed in various conditions. This not only aids in conducting safe and effective laboratory experiments but also in the design of new materials or drugs.

Stoichiometry

Stoichiometry, derived from the Greek words for "element" and "measure," involves the calculation of reactants and products in chemical reactions.
In the step-by-step solution, stoichiometry is used to determine the weight of element A required to combine with an amount of element C, based on known ratios from experiments. Precise stoichiometric calculations are crucial for predicting the amounts of substances needed or produced in a reaction.
By learning stoichiometry, students gain the ability to balance chemical equations, scale reactions up or down, and optimize conditions for desired chemical processes, making it a critical component of chemical education.