Stoichiometry of a Reaction in Solution

Khan Academy
11 May 201010:18
EducationalLearning
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TLDRThe video script outlines a chemistry problem involving the reaction between calcium carbonate and hydrochloric acid. It explains the need to balance the chemical equation and convert given volumes and molarities into moles to determine the mass of calcium carbonate required to react completely with 25 milliliters of a 0.75 molar hydrochloric acid solution. The process involves stoichiometric calculations, emphasizing the importance of understanding molarity and molar mass to find the final mass of the reactant in grams.

Takeaways
  • 🧪 The goal is to determine the mass of calcium carbonate needed to react completely with 25 mL of 0.75 M hydrochloric acid solution.
  • 📝 Before solving the stoichiometry problem, it's essential to balance the chemical equation, ensuring that the number of atoms of each element is the same on both sides.
  • 🌊 The concentration of hydrochloric acid is given as 0.75 moles per liter, which indicates the moles of HCl per liter of solution.
  • 📐 To find the moles of HCl in the 25 mL solution, convert milliliters to liters and then use the molarity to calculate the number of moles.
  • 🔄 The balanced chemical equation shows a 1:2 molar ratio between calcium carbonate and hydrochloric acid, meaning 1 mole of calcium carbonate reacts with 2 moles of HCl.
  • 📊 The calculation starts with 25 mL of 0.75 M HCl solution, converting to liters and then calculating moles: (25 mL * 1 L / 1000 mL) * 0.75 mol/L = 0.01875 moles of HCl.
  • 👉 From the 0.01875 moles of HCl, we find the moles of calcium carbonate required by dividing by 2, resulting in 0.00938 moles of CaCO3 needed.
  • 📈 The molar mass of calcium carbonate (CaCO3) is the sum of the atomic masses of calcium (40), carbon (12), and oxygen (16*3), totaling 100 grams/mole.
  • 🔢 To find the mass of CaCO3, multiply the moles of CaCO3 by its molar mass: 0.00938 moles * 100 g/mole = 0.938 grams.
  • 🎓 Understanding molarity and the concept of moles is crucial for solving stoichiometry problems involving chemical reactions.
  • 📝 Accurate calculations and proper unit conversions are key to obtaining the correct mass of reactants and products in a chemical reaction.
Q & A

  • What is the goal of the video?

    -The goal of the video is to determine the mass of calcium carbonate needed to completely react with 25 milliliters of a 0.75 molar hydrochloric acid solution.

  • What does molarity represent?

    -Molarity represents the moles of a solute, such as hydrochloric acid, per liter of solution.

  • How is the chemical equation balanced in the video?

    -The chemical equation is balanced by ensuring that the number of each type of atom is the same on both the reactant and product sides. In the video, coefficients are adjusted to achieve this balance.

  • How many moles of hydrochloric acid are present in 25 milliliters of a 0.75 molar solution?

    -To find the moles of hydrochloric acid, the volume in milliliters is converted to liters and then multiplied by the molarity. For 25 milliliters of a 0.75 molar solution, the calculation is (25/1000) * 0.75 moles = 0.01875 moles, which rounds to 0.018 moles.

  • What is the stoichiometric ratio between hydrochloric acid and calcium carbonate in this reaction?

    -The stoichiometric ratio between hydrochloric acid and calcium carbonate is 2:1, meaning that 2 moles of hydrochloric acid react with 1 mole of calcium carbonate.

  • How many moles of calcium carbonate are required to react with 0.018 moles of hydrochloric acid?

    -Since the ratio is 2 moles of hydrochloric acid to 1 mole of calcium carbonate, 0.018 moles of hydrochloric acid would require 0.009 moles of calcium carbonate, which is rounded to 0.00938 moles.

  • What is the molar mass of calcium carbonate?

    -The molar mass of calcium carbonate (CaCO3) is the sum of the atomic masses of calcium (40), carbon (12), and three oxygen atoms (16*3), which equals 100 grams per mole.

  • How is the mass of calcium carbonate calculated in the video?

    -The mass of calcium carbonate is calculated by multiplying the moles of calcium carbonate required (0.00938 moles) by its molar mass (100 grams/mole), resulting in 0.938 grams.

  • What is the final mass of calcium carbonate needed to react completely with the given hydrochloric acid solution?

    -The final mass of calcium carbonate needed is 0.938 grams to completely react with 25 milliliters of a 0.75 molar hydrochloric acid solution.

  • Why is it important to balance the chemical equation before performing stoichiometric calculations?

    -Balancing the chemical equation ensures that the law of conservation of mass is followed, meaning that the number and type of atoms must be the same in both reactants and products. This is crucial for accurate stoichiometric calculations.

  • How does the video demonstrate the conversion of volume from milliliters to liters?

    -The video demonstrates the conversion by dividing the volume in milliliters by 1000 to get the volume in liters, as there are 1000 milliliters in a liter.

Outlines
00:00
🧪 Stoichiometry Calculation: Balancing the Equation and Determining Moles

This paragraph introduces the goal of the video, which is to calculate the mass of calcium carbonate needed to react completely with 25 milliliters of a 0.75 M hydrochloric acid solution. It begins by reviewing the chemical equation provided and ensures that it is balanced in terms of calcium, carbon, oxygen, and hydrogen. The speaker then explains the need to convert the given volume and molarity of the hydrochloric acid solution into moles to proceed with the stoichiometric calculations. The process involves converting milliliters to liters and using the molarity to find the moles of HCl present in the solution. The importance of understanding the relationship between molarity, volume, and moles is emphasized to solve the problem effectively.

05:01
📈 Converting Moles to Grams: The Role of Molar Mass

In this paragraph, the speaker continues the stoichiometric calculation by focusing on how to convert the moles of hydrochloric acid to moles of calcium carbonate. It is explained that for every 2 moles of HCl, 1 mole of calcium carbonate is required. The calculation involves multiplying the moles of HCl by the stoichiometric coefficient and dividing by 2 to find the moles of calcium carbonate. The speaker then transitions to finding the mass of calcium carbonate needed by introducing the concept of molar mass. The molar mass of calcium carbonate is calculated by summing the atomic weights of its constituent elements (calcium, carbon, and oxygen). The moles of calcium carbonate are multiplied by its molar mass to obtain the mass in grams, resulting in 0.938 grams as the required mass of calcium carbonate.

10:03
📊 Final Calculation: The Mass of Calcium Carbonate

The final paragraph of the video script presents the culmination of the stoichiometric calculation. After determining the moles of calcium carbonate required for the reaction, the speaker concludes by providing the calculated mass of calcium carbonate needed, which is 0.938 grams. This concise summary reaffirms the result of the previous calculations and provides a clear answer to the initial problem posed in the video. The paragraph wraps up the topic by reinforcing the importance of understanding stoichiometry and molar mass conversions in chemical calculations.

Mindmap
Keywords
💡Stoichiometry
Stoichiometry is the study of the quantitative relationships between reactants and products in chemical reactions. In the context of the video, stoichiometry is used to determine the amount of calcium carbonate needed to react completely with a given volume and concentration of hydrochloric acid. It is a fundamental concept in chemistry that allows for the calculation of mass and moles of substances involved in a reaction based on their balanced chemical equations.
💡Calcium Carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a primary component of minerals such as limestone and marble. In the video, calcium carbonate is the reactant that needs to be quantified for its reaction with hydrochloric acid. The mass of calcium carbonate is determined based on the stoichiometric relationship with hydrochloric acid as outlined in the balanced chemical equation.
💡Hydrochloric Acid
Hydrochloric acid, with the chemical formula HCl, is a strong acid that is commonly used in various chemical reactions, including the one discussed in the video. It is an aqueous solution, meaning it is dissolved in water, and its concentration is measured in molarity, which indicates the number of moles of HCl per liter of solution. In the video, the concentration of hydrochloric acid is given as 0.75 molar, and the volume is specified as 25 milliliters.
💡Molarity
Molarity is a measure of the concentration of a substance in a solution, expressed as moles of the substance per liter of solution. It is crucial in chemistry for understanding the proportions of reactants and products in a reaction. In the video, the molarity of the hydrochloric acid solution is 0.75 moles per liter, which is used to calculate the moles of HCl present in the 25 milliliters of solution.
💡Balanced Chemical Equation
A balanced chemical equation is an equation that obeys the law of conservation of mass, meaning the number and type of atoms on the reactant side (left) must be equal to the number and type of atoms on the product side (right). In the video, the equation is checked for balance to ensure that the reaction is correctly represented before proceeding with the stoichiometric calculations to find the mass of calcium carbonate.
💡Moles
Moles are a fundamental unit in chemistry that represents the amount of substance. One mole of any substance contains Avogadro's number of particles, which is approximately 6.022 x 10^23. In the context of the video, moles are used to quantify the amount of hydrochloric acid and calcium carbonate involved in the reaction, allowing for the calculation of the mass of calcium carbonate required for a complete reaction.
💡Molar Mass
Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all the atoms in a molecule. In the video, the molar mass of calcium carbonate (CaCO3) is determined by adding the atomic masses of calcium (40), carbon (12), and oxygen (16 x 3), resulting in a molar mass of 100 g/mol. This value is used to convert moles of calcium carbonate to grams.
💡Aqueous Solution
An aqueous solution is a mixture in which the solute is dissolved in water. In the video, hydrochloric acid is an example of an aqueous solution, as it is dissolved in water to create a solution with a specific molarity. Understanding the properties of aqueous solutions is essential for working with various chemical reactions, as the solvent's nature can influence reaction rates and equilibrium.
💡Concentration
Concentration in chemistry refers to the amount of a particular substance present in a given volume of solution. It is often expressed in molarity (moles per liter) for solutions. The concentration of a solution is crucial for determining the quantities of reactants and products in a chemical reaction and can affect the rate at which the reaction occurs. In the video, the concentration of hydrochloric acid is given as 0.75 molar, which is used to calculate the moles of HCl present in the 25 milliliters of solution.
💡Reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances into another. It involves the breaking and forming of chemical bonds. In the video, the reaction between calcium carbonate and hydrochloric acid is the central focus, with the goal of determining the mass of calcium carbonate needed to completely react with the given amount of HCl.
💡Mass
Mass in chemistry refers to the amount of matter in an object, typically measured in grams or kilograms. It is a fundamental property that, when combined with molar mass, allows for the calculation of the number of moles of a substance. In the video, the ultimate goal is to find the mass of calcium carbonate required for the reaction, which is determined through stoichiometric calculations based on the moles of reactants and their molar masses.
Highlights

The video aims to calculate the mass of calcium carbonate needed to react completely with a 25 mL 0.75 M hydrochloric acid solution.

The chemical equation for the reaction between calcium carbonate and hydrochloric acid must be balanced before proceeding with stoichiometric calculations.

The balanced chemical equation shows a 1:1:1:2 ratio of calcium, carbon, oxygen, and hydrogen atoms respectively.

To balance the reaction, a coefficient of 2 is placed in front of the hydrochloric acid, resulting in a balanced equation with 2 chlorine atoms on both sides.

The problem is unique because the mass of hydrochloric acid is not given; instead, the volume and molarity of the solution are provided.

The first step in solving the problem is to convert the volume of the hydrochloric acid solution from milliliters to liters.

The molarity of the solution is used to calculate the moles of hydrochloric acid present in the given volume of the solution.

For every 2 moles of hydrochloric acid, 1 mole of calcium carbonate is required for the reaction to proceed.

The moles of hydrochloric acid are calculated to be 0.01875 moles, which is approximately 0.018 moles after rounding.

The required moles of calcium carbonate are then determined by dividing the moles of hydrochloric acid by 2, resulting in 0.00938 moles.

The molar mass of calcium carbonate is calculated to be 100 grams per mole by summing the atomic masses of its constituent elements.

Finally, the mass of calcium carbonate needed is found by multiplying the moles of calcium carbonate by its molar mass, yielding 0.938 grams.

The process involves converting units from milliliters to liters and from moles to grams using precise mathematical operations.

The video demonstrates the importance of balancing chemical equations and understanding molarity when performing stoichiometric calculations.

The example serves as a practical application of stoichiometry, showcasing how to determine the reactants needed for a complete reaction.

The video provides a step-by-step guide on how to approach and solve stoichiometric problems involving the calculation of mass based on given volumes and molarities.

The problem-solving approach in the video emphasizes the significance of unit conversion and the use of molar mass in chemical calculations.

The video is an educational resource that effectively teaches the principles of chemical reactions and the calculations necessary to predict their outcomes.

Transcripts

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Chemistry ExperimentStoichiometry CalculationAcid-Base ReactionHydrochloric AcidCalcium CarbonateMolarity ConversionMoles to MassChemical BalanceEducational ContentScience Education