A Weighed Sample Of Crystalline Sodium Carbonate $\left( Na_2CO_{3} \cdot NH_2O \right$\] Was Heated In A Crucible Until There Was No Further Change In Mass. The Mass Of The Sample Reduced By $14.5\%$. Calculate The Number Of Moles (n)
Introduction
In chemistry, the calculation of the number of moles of a substance is a fundamental concept that plays a crucial role in understanding various chemical reactions and processes. In this article, we will discuss how to calculate the number of moles of crystalline sodium carbonate, which is a common compound used in various industrial and laboratory applications.
Theoretical Background
Sodium carbonate, also known as washing soda, is a crystalline compound with the chemical formula Na2CO3. It is commonly used as a cleaning agent, a water softener, and in the manufacture of glass, paper, and textiles. The compound can exist in different forms, including anhydrous and hydrated forms, which are denoted by the number of water molecules (n) in the formula Na2CO3 Ā· nH2O.
Experimental Procedure
In this experiment, a weighed sample of crystalline sodium carbonate was heated in a crucible until there was no further change in mass. The mass of the sample was reduced by 14.5%. To calculate the number of moles of the compound, we need to determine the mass of the anhydrous form of sodium carbonate.
Calculations
Let's assume that the initial mass of the sample is m (in grams). Since the mass of the sample reduced by 14.5%, the mass of the anhydrous form of sodium carbonate is:
m_anhydrous = m - (0.145 * m)
m_anhydrous = 0.855m
The molar mass of anhydrous sodium carbonate (Na2CO3) is 105.99 g/mol. To calculate the number of moles (n) of the compound, we can use the following formula:
n = m_anhydrous / M
where M is the molar mass of the compound.
Substitution and Simplification
Substituting the expression for m_anhydrous into the formula for n, we get:
n = (0.855m) / M
n = (0.855m) / 105.99
Simplification
To simplify the expression, we can cancel out the units of mass (g) by dividing both the numerator and the denominator by the molar mass of the compound (105.99 g/mol).
n = (0.855 * 1) / (105.99 * 1)
n = 0.00805
Conclusion
In this article, we discussed how to calculate the number of moles of crystalline sodium carbonate using the mass of the anhydrous form of the compound. We assumed that the initial mass of the sample was m (in grams) and that the mass of the sample reduced by 14.5%. We used the molar mass of anhydrous sodium carbonate (105.99 g/mol) to calculate the number of moles (n) of the compound.
Calculating the Number of Moles: A Step-by-Step Guide
Step 1: Determine the Mass of the Anhydrous Form of Sodium Carbonate
The mass of the anhydrous form of sodium carbonate is given by:
m_anhydrous = m - (0.145 * m)
m_anhydrous = 0.855m
Step 2: Calculate the Number of Moles of the Compound
The number of moles (n) of the compound is given by:
n = m_anhydrous / M
where M is the molar mass of the compound.
Step 3: Simplify the Expression
To simplify the expression, we can cancel out the units of mass (g) by dividing both the numerator and the denominator by the molar mass of the compound (105.99 g/mol).
n = (0.855 * 1) / (105.99 * 1)
n = 0.00805
Step 4: Interpret the Results
The calculated value of n represents the number of moles of crystalline sodium carbonate in the sample.
Common Applications of Sodium Carbonate
Sodium carbonate is a versatile compound with a wide range of applications in various industries. Some of the common applications of sodium carbonate include:
- Cleaning Agent: Sodium carbonate is used as a cleaning agent in various household and industrial applications.
- Water Softener: Sodium carbonate is used to soften water by removing calcium and magnesium ions.
- Glass Manufacturing: Sodium carbonate is used in the manufacture of glass, paper, and textiles.
- Pharmaceuticals: Sodium carbonate is used as an excipient in various pharmaceutical applications.
Conclusion
Q: What is the chemical formula of crystalline sodium carbonate?
A: The chemical formula of crystalline sodium carbonate is Na2CO3 Ā· nH2O, where n represents the number of water molecules in the compound.
Q: What is the molar mass of anhydrous sodium carbonate?
A: The molar mass of anhydrous sodium carbonate (Na2CO3) is 105.99 g/mol.
Q: How do I calculate the number of moles of crystalline sodium carbonate?
A: To calculate the number of moles of crystalline sodium carbonate, you need to determine the mass of the anhydrous form of the compound and then divide it by the molar mass of the compound.
Q: What is the formula for calculating the number of moles of crystalline sodium carbonate?
A: The formula for calculating the number of moles of crystalline sodium carbonate is:
n = m_anhydrous / M
where m_anhydrous is the mass of the anhydrous form of the compound and M is the molar mass of the compound.
Q: How do I determine the mass of the anhydrous form of sodium carbonate?
A: To determine the mass of the anhydrous form of sodium carbonate, you need to subtract the mass of the water molecules from the initial mass of the sample.
Q: What is the significance of the molar mass of a compound?
A: The molar mass of a compound is the mass of one mole of the compound, expressed in grams per mole (g/mol). It is a fundamental concept in chemistry that plays a crucial role in understanding various chemical reactions and processes.
Q: Can I use the formula for calculating the number of moles of crystalline sodium carbonate for other compounds?
A: Yes, you can use the formula for calculating the number of moles of crystalline sodium carbonate for other compounds, as long as you know the molar mass of the compound and the mass of the anhydrous form of the compound.
Q: What are some common applications of sodium carbonate?
A: Some common applications of sodium carbonate include:
- Cleaning Agent: Sodium carbonate is used as a cleaning agent in various household and industrial applications.
- Water Softener: Sodium carbonate is used to soften water by removing calcium and magnesium ions.
- Glass Manufacturing: Sodium carbonate is used in the manufacture of glass, paper, and textiles.
- Pharmaceuticals: Sodium carbonate is used as an excipient in various pharmaceutical applications.
Q: How do I ensure the accuracy of my calculations?
A: To ensure the accuracy of your calculations, you need to:
- Use the correct formula: Use the correct formula for calculating the number of moles of crystalline sodium carbonate.
- Know the molar mass of the compound: Know the molar mass of the compound and the mass of the anhydrous form of the compound.
- Use accurate measurements: Use accurate measurements of the mass of the sample and the molar mass of the compound.
- Check your calculations: Check your calculations for errors and inconsistencies.
Conclusion
In conclusion, calculating the number of moles of crystalline sodium carbonate is a fundamental concept in chemistry that plays a crucial role in understanding various chemical reactions and processes. By following the step-by-step guide outlined in this article and answering the frequently asked questions, you can ensure the accuracy of your calculations and apply the concept to other compounds.