How to Calculate Mass Percent of a Solution

Chem Academy
10 Jul 201511:16
EducationalLearning
32 Likes 10 Comments

TLDRIn this educational video, Mr. Millings explains the concept of mass percent, a method to calculate the composition of a solution. He demonstrates how to determine the mass percent of a solute in a solution by dividing the mass of the solute by the total mass of the solution and multiplying by 100. Using examples, he illustrates the process of calculating mass percent for different scenarios, including dissolving NaCl in water to create a saltwater solution and determining the mass of lactose in cow's milk. The video also covers how to manipulate the mass percent formula to find the mass of solute or the entire solution, providing clear steps and examples for better understanding.

Takeaways
  • 🧪 Mass percent is a way to calculate the composition of a solution by determining the proportion of solute in the solution.
  • 📚 The formula for mass percent is: (mass of solute / mass of entire solution) * 100%.
  • 💧 A solution is made up of two components: the solute (the substance being dissolved) and the solvent (usually water).
  • 📉 To find the mass of the entire solution, you add the mass of the solute to the mass of the solvent.
  • 🧂 An example provided was dissolving 15 grams of NaCl (salt) in 100 grams of water, resulting in a 13% mass percent of salt in the solution.
  • 🔢 The concept of significant figures is important when calculating and reporting the mass percent to ensure accuracy.
  • 🔄 The mass percent formula can be rearranged to solve for either the mass of the solute or the mass of the solution.
  • 📝 In a problem-solving scenario, if given the mass of the solute and solvent, you can calculate the mass percent of the solute in the solution.
  • 🥛 Another example involved calculating the mass of lactose in cow's milk, given that milk contains 4.5% lactose by mass.
  • 🧪 Lastly, the script demonstrated how to calculate the mass of a solution when given the mass of the solute and the desired mass percent of the solution, as shown with a 15% sodium nitrate solution.
  • 👍 The video encourages viewers to subscribe for more educational content, highlighting the importance of engaging with the audience.
Q & A

  • What is mass percent and how is it calculated?

    -Mass percent is a measure of the concentration of a solute in a solution. It is calculated by dividing the mass of the solute by the total mass of the solution (solute plus solvent) and then multiplying by 100 to get a percentage.

  • What are the two components of a solution?

    -A solution consists of two parts: the solute, which is the substance that is dissolved, and the solvent, which is the substance that dissolves the solute.

  • How many grams of NaCl are used in the example to make a saltwater solution?

    -In the example provided, 15 grams of NaCl (sodium chloride) are used to make a saltwater solution.

  • What is the mass of water used in the saltwater solution example?

    -100 grams (or 100 milliliters, since the density of water is 1 gram per milliliter) of water is used in the saltwater solution example.

  • What is the mass percent of the salt in the saltwater solution example?

    -The mass percent of the salt in the example saltwater solution is 13%.

  • How can the mass percent formula be manipulated to solve for the mass of the solute?

    -To solve for the mass of the solute, you can use the formula: mass of solute = (mass of solution * mass percent) / 100.

  • How can you determine the mass of the solution if given the mass of the solute and the mass percent?

    -To determine the mass of the solution, use the formula: mass of solution = (mass of solute * 100) / mass percent.

  • In the example problem involving salt and water, what is the mass percent of salt in the solution?

    -In the example problem where 25.5 grams of salt is mixed with 150 grams of water, the mass percent of salt in the solution is 14.5%.

  • How many grams of lactose are present in 175 grams of cow's milk if it contains 4.5% lactose by mass?

    -In 175 grams of cow's milk with 4.5% lactose by mass, there are 7.9 grams of lactose.

  • If 75 grams of sodium nitrate is used to make a 15% solution, what is the mass of the solution?

    -If 75 grams of sodium nitrate is used to make a 15% solution, the mass of the solution is 500 grams.

Outlines
00:00
🧪 Introduction to Mass Percent in Solutions

In this introductory segment, Mr. Millings explains the concept of mass percent, which is a method used to calculate the composition of a solution. He illustrates how to determine the mass percent by dividing the mass of the solute (substance dissolved) by the total mass of the solution (solute plus solvent) and then multiplying by 100. An example is provided using 15 grams of NaCl (salt) dissolved in 100 grams of water, resulting in a 13% mass percent of salt in the solution. The importance of understanding solutions as consisting of solute and solvent is emphasized, and the formula for mass percent is introduced and explained.

05:01
🔍 Calculating Mass Percent with Examples

This paragraph delves into applying the mass percent formula to various examples. The first example involves calculating the mass percent of a solution made by mixing 25.5 grams of salt with 150 grams of water, resulting in a 14.5% mass percent of salt. The second example addresses a real-world scenario where cow's milk contains 4.5% lactose by mass, and the task is to find out how much lactose is present in 175 grams of milk. Using the mass percent formula, it is determined that there are 7.9 grams of lactose in the given amount of milk. These examples demonstrate the practical application of the mass percent formula in solving problems related to the composition of solutions.

10:01
📚 Advanced Application of Mass Percent Formula

The final paragraph focuses on the advanced application of the mass percent formula to solve for different variables. The example given involves dissolving 75 grams of sodium nitrate to create a 15% solution and determining the total mass of the solution. By manipulating the mass percent formula, Mr. Millings shows how to calculate the mass of the solution when the mass of the solute and the desired mass percent are known. The calculation leads to a 500-gram solution, highlighting the versatility of the mass percent formula in solving for mass of solute, mass percent, or total mass of a solution.

Mindmap
Keywords
💡Mass Percent
Mass percent is a measure of the concentration of a solute in a solution. It is calculated by dividing the mass of the solute by the total mass of the solution and then multiplying by 100 to get a percentage. In the video's theme, mass percent is the central concept used to understand how much of a solute is present in a given solution. For example, the script explains how to calculate the mass percent of salt in a saltwater solution by dividing 15 grams of NaCl by the total mass of the solution (115 grams) and then multiplying by 100 to get 13%.
💡Solute
A solute is the substance that is dissolved in a solvent to form a solution. It is one of the two main components of a solution, the other being the solvent. In the context of the video, NaCl (sodium chloride or salt) is the solute in the saltwater solution example. The mass of the solute is a key factor in calculating the mass percent, as demonstrated when 15 grams of NaCl is used in the calculation.
💡Solvent
A solvent is a substance, usually a liquid, that dissolves a solute to form a solution. Water is a common solvent and is used in many solutions, including the examples provided in the script. The mass of the solvent, when combined with the mass of the solute, gives the total mass of the solution, which is necessary for determining the mass percent.
💡Solution
A solution is a homogeneous mixture of two or more substances. In the video, the term solution refers to a mixture where a solute is dissolved in a solvent. The script discusses calculating the mass percent of a solution, such as a saltwater solution, to understand the concentration of the solute within it.
💡Density
Density is a measure of mass per unit volume of a substance. The script mentions the density of water, which is 1 gram per milliliter. This information is used to convert the volume of water (100 milliliters) into mass (100 grams) for the purpose of calculating the mass percent of the solution.
💡Significant Figures (Sigfig)
Significant figures are the digits in a number that carry meaning contributing to its precision. The script emphasizes the importance of using the correct number of significant figures when performing calculations and reporting results, such as rounding the mass percent of salt in the solution to 13% instead of 13.0%.
💡Lactose
Lactose is a sugar found in milk. In the script, lactose serves as an example of a solute in the context of cow's milk, which contains 4.5% lactose by mass. The video uses this information to demonstrate how to calculate the mass of lactose in a given mass of milk.
💡Sodium Nitrate
Sodium nitrate is a chemical compound used in the script as an example of a solute. The video presents a problem where 75 grams of sodium nitrate is dissolved to make a 15% solution, and the viewer is guided to calculate the total mass of the resulting solution.
💡Concentration
Concentration in the context of solutions refers to the amount of solute present in a given amount of solvent, typically expressed as a percentage or ratio. The mass percent formula is a way to express the concentration of a solute in a solution, as shown in the video's examples.
💡Formula Manipulation
Formula manipulation refers to the mathematical process of rearranging an equation to solve for a different variable. In the script, the mass percent formula is manipulated to solve for either the mass of the solute or the mass of the solution, depending on the information provided in various problems.
Highlights

Introduction to mass percent and its significance in calculating the composition of a solution.

Explanation of mass percent formula: mass of solute divided by mass of the entire solution, multiplied by 100.

Illustration of how to calculate mass percent with an example using 15 grams of NaCl and 100 grams of water.

Conversion of 100 milliliters of water to 100 grams based on the density of water being 1 gram per milliliter.

Calculation resulting in a 13% mass percent saltwater solution using significant figures.

Presentation of three different formulas derived from the mass percent formula to solve for mass percent, mass of solute, or mass of solution.

Example problem: Calculating the mass percent of salt in a solution made with 25.5 grams of salt and 150 grams of water.

Result of the example problem showing a 14.5% mass percent of sodium chloride in the solution.

Application of the mass percent formula to determine the mass of lactose in 175 grams of cow's milk with 4.5% lactose content.

Calculation revealing 7.9 grams of lactose in the given amount of cow's milk.

Another example problem involving determining the mass of a solution with 75 grams of sodium nitrate to make a 15% solution.

Final calculation showing the mass of the solution to be 500 grams.

Emphasis on using the correct number of significant figures in calculations for accuracy.

Encouragement for viewers to subscribe for more educational content.

Transcripts

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ChemistryMass PercentSoluteSolventTutorialEducationScienceCalculationSodium ChlorideLactose