A Pure Sample Of A Compound Contains 80 % 80\% 80% Carbon And 20 % 20\% 20% Hydrogen By Mass.Which Of The Following Is The Empirical Formula Of The Compound?Choose 1 Answer:A. C H 3 CH_3 C H 3 ​ B. C H 4 CH_4 C H 4 ​ C. C 2 H 6 C_2H_6 C 2 ​ H 6 ​ D. C 2 H 8 C_2H_8 C 2 ​ H 8 ​

Introduction

In chemistry, determining the empirical formula of a compound is a crucial step in understanding its composition and properties. The empirical formula represents the simplest whole-number ratio of atoms of each element present in the compound. In this article, we will explore how to determine the empirical formula of a compound given its mass percentage composition.

Mass Percentage Composition

The mass percentage composition of a compound is a way to express the percentage of each element present in the compound by mass. In this case, we are given that a pure sample of a compound contains $80\%$ carbon and $20\%$ hydrogen by mass.

Calculating the Number of Moles

To determine the empirical formula, we need to calculate the number of moles of each element present in the compound. We can do this by assuming a $100\,g$ sample of the compound and calculating the number of moles of each element.

Let's assume we have a $100\,g$ sample of the compound. The mass of carbon present in the sample is $80\,g$, and the mass of hydrogen present is $20\,g$.

We can calculate the number of moles of each element using the following formulas:

$$n_{C} = \frac{m_{C}}{M_{C}}$$

$$n_{H} = \frac{m_{H}}{M_{H}}$$

where $n$ is the number of moles, $m$ is the mass, and $M$ is the molar mass.

The molar mass of carbon is $12.01\,g/mol$, and the molar mass of hydrogen is $1.008\,g/mol$.

Plugging in the values, we get:

$$n_{C} = \frac{80\,g}{12.01\,g/mol} = 6.66\,mol$$

$$n_{H} = \frac{20\,g}{1.008\,g/mol} = 19.88\,mol$$

Determining the Empirical Formula

Now that we have the number of moles of each element, we can determine the empirical formula of the compound. To do this, we need to find the simplest whole-number ratio of atoms of each element present in the compound.

We can do this by dividing the number of moles of each element by the smallest number of moles.

In this case, the smallest number of moles is $6.66\,mol$, which is the number of moles of carbon.

Dividing the number of moles of each element by the smallest number of moles, we get:

$$\frac{n_{C}}{n_{C,min}} = \frac{6.66\,mol}{6.66\,mol} = 1$$

$$\frac{n_{H}}{n_{C,min}} = \frac{19.88\,mol}{6.66\,mol} = 3$$

Therefore, the empirical formula of the compound is $CH_3$.

Conclusion

In conclusion, we have determined the empirical formula of a compound given its mass percentage composition. We assumed a $100\,g$ sample of the compound and calculated the number of moles of each element present in the sample. We then determined the empirical formula by finding the simplest whole-number ratio of atoms of each element present in the compound.

The empirical formula of the compound is $CH_3$.

References

• Chemistry: An Atoms First Approach, by Steven S. Zumdahl
• General Chemistry: Principles and Modern Applications, by Linus Pauling

Answer

The correct answer is:

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Introduction

In our previous article, we explored how to determine the empirical formula of a compound given its mass percentage composition. In this article, we will answer some frequently asked questions related to determining the empirical formula of a compound.

Q: What is the empirical formula of a compound?

A: The empirical formula of a compound is the simplest whole-number ratio of atoms of each element present in the compound.

Q: How do I determine the empirical formula of a compound?

A: To determine the empirical formula of a compound, you need to follow these steps:

1. Calculate the number of moles of each element present in the compound.
2. Divide the number of moles of each element by the smallest number of moles.
3. The resulting ratio is the empirical formula of the compound.

Q: What is the difference between the empirical formula and the molecular formula of a compound?

A: The empirical formula of a compound represents the simplest whole-number ratio of atoms of each element present in the compound, while the molecular formula represents the actual number of atoms of each element present in a molecule of the compound.

Q: How do I calculate the number of moles of each element present in a compound?

A: To calculate the number of moles of each element present in a compound, you need to use the following formula:

$$n = \frac{m}{M}$$

where $n$ is the number of moles, $m$ is the mass of the element, and $M$ is the molar mass of the element.

Q: What is the molar mass of an element?

A: The molar mass of an element is the mass of one mole of the element, usually expressed in grams per mole (g/mol).

Q: How do I determine the molar mass of an element?

A: To determine the molar mass of an element, you need to know the atomic mass of the element, which is the mass of one atom of the element. You can find the atomic mass of an element in a periodic table.

Q: What is the atomic mass of an element?

A: The atomic mass of an element is the mass of one atom of the element, usually expressed in atomic mass units (amu).

Q: How do I convert atomic mass units (amu) to grams per mole (g/mol)?

A: To convert atomic mass units (amu) to grams per mole (g/mol), you need to use the following conversion factor:

$$1\,amu = \frac{1\,g}{6.022 \times 10^{23}\,mol}$$

Q: What is the significance of the empirical formula of a compound?

A: The empirical formula of a compound is significant because it represents the simplest whole-number ratio of atoms of each element present in the compound, which is useful in understanding the properties and behavior of the compound.

Conclusion

In conclusion, determining the empirical formula of a compound is an important step in understanding the properties and behavior of the compound. By following the steps outlined in this article, you can determine the empirical formula of a compound given its mass percentage composition.

References

• Chemistry: An Atoms First Approach, by Steven S. Zumdahl
• General Chemistry: Principles and Modern Applications, by Linus Pauling

Answer

The correct answers to the questions are:

Q1: The empirical formula of a compound is the simplest whole-number ratio of atoms of each element present in the compound. Q2: To determine the empirical formula of a compound, you need to calculate the number of moles of each element present in the compound, divide the number of moles of each element by the smallest number of moles, and the resulting ratio is the empirical formula of the compound. Q3: The empirical formula of a compound represents the simplest whole-number ratio of atoms of each element present in the compound, while the molecular formula represents the actual number of atoms of each element present in a molecule of the compound. Q4: To calculate the number of moles of each element present in a compound, you need to use the formula n = m/M, where n is the number of moles, m is the mass of the element, and M is the molar mass of the element. Q5: The molar mass of an element is the mass of one mole of the element, usually expressed in grams per mole (g/mol). Q6: To determine the molar mass of an element, you need to know the atomic mass of the element, which is the mass of one atom of the element. Q7: The atomic mass of an element is the mass of one atom of the element, usually expressed in atomic mass units (amu). Q8: To convert atomic mass units (amu) to grams per mole (g/mol), you need to use the conversion factor 1 amu = 1 g / 6.022 x 10^23 mol. Q9: The empirical formula of a compound is significant because it represents the simplest whole-number ratio of atoms of each element present in the compound, which is useful in understanding the properties and behavior of the compound.