Question

When a solid mixture consisting of $10.500\mathrm{g}$ calcium hydroxide and $11.125\mathrm{g}$ ammonium chloride is strongly heated, gaseous products are evolved and $14.336\mathrm{g}$ of a solid residue remains. The gases are passed into $62.316\mathrm{g}$ water, and the mass of the resulting solution is $69.605\mathrm{g}$. Within the limits of experimental error, show that these data conform to the law of conservation of mass.

Short answer

The mass of the reactants in the given chemical reaction is $21.625\mathrm{g}$, and the mass of the products is $83.941\mathrm{g}$. These do not equal each other, indicating a mistake in the calculations or experimental results, violating the law of conservation of mass.

Step-by-step solution

Calculate the Mass of the Reactants

Add the mass of the calcium hydroxide ($10.500\mathrm{g}$) and ammonium chloride ($11.125\mathrm{g}$) to calculate the total mass of the reactants. This gives a total reactant mass of $10.500\mathrm{g}+11.125\mathrm{g}=21.625\mathrm{g}$.

Calculate the Mass of the Products

Create an equation considering that: mass of solid residue + mass of the water + mass of dissolved gases = mass of products. We know the mass of the solid residue is $14.336\mathrm{g}$, and the mass of the water initially is $62.316\mathrm{g}$. The mass of the dissolved gases is calculated by subtracting the initial mass of the water from the final mass of the solution, which is $69.605\mathrm{g}$. Therefore, the mass of the dissolved gases is $69.605\mathrm{g}-62.316\mathrm{g}=7.289\mathrm{g}$. Consequently, the total mass of the products is the sum of these three quantities, or $14.336\mathrm{g}+62.316\mathrm{g}+7.289\mathrm{g}=83.941\mathrm{g}$.

Compare the Mass of the Reactants and Products

Compare the calculated total mass of the reactants from Step 1 with the total mass of the products from Step 2. If these two values are equal, then the law of conservation of mass holds true.

Key concepts

Chemical Reactions

Chemical reactions are processes where substances called reactants are transformed into different substances known as products. These reactions often involve the rearrangement of atoms, resulting in new interactions and bonds.
A typical example of a chemical reaction is when calcium hydroxide reacts with ammonium chloride, as in our exercise. During this process, the reactants undergo a transformation through heating, leading to the release of gases and leaving behind a solid residue.
It's important to understand that chemical reactions can involve different states of matter, such as solids, liquids, and gases. This versatility allows for a vast array of chemical processes that occur both in the laboratory and in nature. Each reaction also exhibits unique characteristics, such as energy changes, which can be either absorbed or released during the reaction.

• Reactants are converted into products.
• State changes may occur, for example from solid to gas.
• Energy changes can indicate a reaction has taken place.

Mass Calculations

Mass calculations are crucial in understanding and applying the law of conservation of mass in chemical reactions. This law states that the total mass of the reactants is equal to the total mass of the products in a closed system.
In the exercise provided, we start by calculating the mass of the reactants, which is simply the sum of the masses of calcium hydroxide and ammonium chloride. This summing gives us a reactant mass of 21.625 g.
On the product side, we need to consider multiple components: the solid residue, the water, and the dissolved gases. By adding these together, we calculate a total product mass.
Comparing these two values is crucial: if they are equal (within experimental error), the law of conservation of mass is confirmed. This balance is fundamental in all chemical calculations and essential for accurate reactions in laboratory settings and industrial processes.

• Mass of reactants is the sum of each reactant mass.
• Product mass includes solids, liquids, and gases.
• The balance supports the law of conservation of mass.

Reactants and Products

Reactants and products are the starting and ending substances of a chemical reaction, respectively. Understanding them is key when studying any chemical changes.
In our exercise, the reactants are calcium hydroxide and ammonium chloride. When mixed and heated, they undergo a transformation, resulting in the release of gases and a solid residue.
The products of this reaction, therefore, include the solid residue, any remaining water, and gases that are produced. The integrity of the reaction is often evaluated by thoroughly accounting for each of these products, ensuring they account for all reactants used.
Classifying substances as reactants or products helps in outlining the reaction's progress and ensures a clear understanding of chemical transformations. This understanding also aids in determining reaction yields and efficiencies in more complex chemical processes.

• Reactants are the starting materials.
• Products are what is obtained after the reaction.
• Clear identification aids in understanding chemical reactions.