Question

If \(1.00 \mathrm{~g}\) of gray zinc powder reacts with \(0.49 \mathrm{~g}\) of yellow sulfur powder, what is the mass of the zinc sulfide product?

Short answer

The mass of the zinc sulfide product is 1.49 g.

Step-by-step solution

Understand the Reaction

The reaction between zinc (Zn) and sulfur (S) forms zinc sulfide (ZnS). The chemical equation is:\[ \text{Zn} + \text{S} \rightarrow \text{ZnS} \]

Use the Law of Conservation of Mass

The law of conservation of mass states that the mass of the reactants equals the mass of the products. Thus, the total mass of the zinc and sulfur will equal the mass of zinc sulfide produced.

Calculate Total Mass of Reactants

Add the masses of the zinc and sulfur used in the reaction: The total mass is: \[ 1.00 \text{ g (Zn)} + 0.49 \text{ g (S)} = 1.49 \text{ g} \].

Determine the Mass of the Zinc Sulfide Product

According to the conservation of mass, the total mass of the product, zinc sulfide, is equal to the total mass of the reactants calculated in Step 3. Therefore, the mass of zinc sulfide produced is:\[ 1.49 \text{ g} \].

Key concepts

Law of Conservation of Mass

The law of conservation of mass is a fundamental principle in chemistry that states that mass is neither created nor destroyed in a chemical reaction. This means that the total mass of the reactants, the substances you start with, is always equal to the total mass of the products, the substances you end up with.
This is crucial in predicting the outcomes of reactions. For instance, in our zinc and sulfur example, the initial masses are 1.00 g of zinc and 0.49 g of sulfur. According to this law, the zinc sulfide produced must have a total mass of 1.49 g, which is simply the sum of the starting materials.

• This helps ensure that calculations in chemistry remain balanced and accurate.
• It implies that during any reaction, atoms are merely rearranged, not lost or added.

You use this principle to confirm whether a reaction equation is correctly balanced or not by comparing the mass of substances on each side of the equation.

Stoichiometry

Stoichiometry is like the arithmetic of chemistry. It involves using relationships between reactants and products in a chemical equation to perform calculations.
When performing stoichiometric calculations, you start with a balanced chemical equation. This balances the number of atoms for each element on both sides.

In the zinc sulfide reaction, you've already balanced the equation:

• Zn + S ⟶ ZnS
• This shows that one atom of zinc reacts with one atom of sulfur to form one molecule of zinc sulfide.

Now, stoichiometry will help you determine how much product can be formed from a given amount of reactants, or how much of a reactant you need to make a specific amount of product.
In our example, we used the ratio of 1 mole of zinc to 1 mole of sulfur, reflecting their atomic masses in grams, to achieve a total mass balance.

Zinc Sulfide

Zinc sulfide (ZnS) is a compound formed by the combination of zinc and sulfur. Its appearance ranges from white to yellowish, depending on any impurities present.
Zinc sulfide is utilized in various applications:

• As a pigment called lithopone.
• In the manufacture of luminescent materials.
• Part of the components in making infrared optics.

The formation of zinc sulfide through the reaction of zinc and sulfur is classic. It's a straightforward synthesis that illustrates key chemical concepts like stoichiometry and the conservation of mass.
Zinc sulfide's production can be noticed readily because it often involves a visible reaction process, such as emission of light, under specific circumstances.