How Many Grams Are There In 4.5 × 10 22 4.5 \times 10^{22} 4.5 × 1 0 22 Molecules Of B A ( N O 2 ) 2 Ba(NO_2)_2 B A ( N O 2 ​ ) 2 ​ ?2. How Many Molecules Are There In 9.34 Grams Of L I C L LiCl L I Cl ?3. How Many Grams Do 4.3 × 10 21 4.3 \times 10^{21} 4.3 × 1 0 21 Molecules Of U F 6 UF_6 U F 6 ​ Weigh?4.

Chemistry is a vast and fascinating field that deals with the study of matter, its properties, and the changes it undergoes. One of the fundamental concepts in chemistry is the calculation of molecular weight and the number of molecules present in a given sample. In this article, we will explore four different scenarios that involve calculating the number of grams in a given number of molecules of a compound, and vice versa.

Scenario 1: Calculating the Number of Grams in a Given Number of Molecules

Problem Statement

How many grams are there in $4.5 \times 10^{22}$ molecules of $Ba(NO_2)_2$?

Solution

To solve this problem, we need to calculate the molecular weight of $Ba(NO_2)_2$. The atomic weights of the elements present in the compound are:

• Barium (Ba): 137.33 g/mol
• Nitrogen (N): 14.01 g/mol
• Oxygen (O): 16.00 g/mol

The molecular weight of $Ba(NO_2)_2$ can be calculated as follows:

Molecular weight of $Ba(NO_2)_2$ = 137.33 + 2(14.01) + 4(16.00) = 137.33 + 28.02 + 64.00 = 229.35 g/mol

Now that we have the molecular weight of $Ba(NO_2)_2$, we can calculate the number of grams in $4.5 \times 10^{22}$ molecules of the compound.

Number of grams = Number of molecules $\times$ Molecular weight = $4.5 \times 10^{22}$ $\times$ 229.35 g/mol = $1.03 \times 10^{26}$ g

Therefore, there are $1.03 \times 10^{26}$ grams in $4.5 \times 10^{22}$ molecules of $Ba(NO_2)_2$.

Scenario 2: Calculating the Number of Molecules in a Given Mass

Problem Statement

How many molecules are there in 9.34 grams of $LiCl$?

Solution

To solve this problem, we need to calculate the molecular weight of $LiCl$. The atomic weights of the elements present in the compound are:

• Lithium (Li): 6.94 g/mol
• Chlorine (Cl): 35.45 g/mol

The molecular weight of $LiCl$ can be calculated as follows:

Molecular weight of $LiCl$ = 6.94 + 35.45 = 42.39 g/mol

Now that we have the molecular weight of $LiCl$, we can calculate the number of molecules in 9.34 grams of the compound.

Number of molecules = Mass of the compound / Molecular weight = 9.34 g / 42.39 g/mol = $2.20 \times 10^{21}$ molecules

Therefore, there are $2.20 \times 10^{21}$ molecules in 9.34 grams of $LiCl$.

Scenario 3: Calculating the Mass of a Given Number of Molecules

Problem Statement

How many grams do $4.3 \times 10^{21}$ molecules of $UF_6$ weigh?

Solution

To solve this problem, we need to calculate the molecular weight of $UF_6$. The atomic weights of the elements present in the compound are:

• Uranium (U): 238.03 g/mol
• Fluorine (F): 19.00 g/mol

The molecular weight of $UF_6$ can be calculated as follows:

Molecular weight of $UF_6$ = 238.03 + 6(19.00) = 238.03 + 114.00 = 352.03 g/mol

Now that we have the molecular weight of $UF_6$, we can calculate the mass of $4.3 \times 10^{21}$ molecules of the compound.

Mass of the compound = Number of molecules $\times$ Molecular weight = $4.3 \times 10^{21}$ $\times$ 352.03 g/mol = $1.51 \times 10^{24}$ g

Therefore, $4.3 \times 10^{21}$ molecules of $UF_6$ weigh $1.51 \times 10^{24}$ grams.

Scenario 4: Calculating the Number of Molecules in a Given Mass

Problem Statement

How many molecules are there in 5.67 grams of $CaF_2$?

Solution

To solve this problem, we need to calculate the molecular weight of $CaF_2$. The atomic weights of the elements present in the compound are:

• Calcium (Ca): 40.08 g/mol
• Fluorine (F): 19.00 g/mol

The molecular weight of $CaF_2$ can be calculated as follows:

Molecular weight of $CaF_2$ = 40.08 + 2(19.00) = 40.08 + 38.00 = 78.08 g/mol

Now that we have the molecular weight of $CaF_2$, we can calculate the number of molecules in 5.67 grams of the compound.

Number of molecules = Mass of the compound / Molecular weight = 5.67 g / 78.08 g/mol = $7.28 \times 10^{19}$ molecules

Therefore, there are $7.28 \times 10^{19}$ molecules in 5.67 grams of $CaF_2$.

Conclusion

In this article, we have explored four different scenarios that involve calculating the number of grams in a given number of molecules of a compound, and vice versa. We have used the concept of molecular weight and the Avogadro's number to solve these problems. The molecular weight of a compound is calculated by summing the atomic weights of the elements present in the compound, and the Avogadro's number is used to convert the number of molecules to the number of grams and vice versa. These calculations are essential in chemistry and are used to determine the properties and behavior of compounds.

References

• CRC Handbook of Chemistry and Physics, 97th Edition
• Atkins, P. W., & De Paula, J. (2010). Physical Chemistry. Oxford University Press.
• Chang, R. (2010). Chemistry. McGraw-Hill.

Further Reading

• Molecular Weight and Mole Calculations in Chemistry
• Avogadro's Number and the Mole
• Atomic Weights and the Periodic Table
  Frequently Asked Questions (FAQs) on Molecular Weight and Mole Calculations ================================================================================

In this article, we will address some of the most frequently asked questions on molecular weight and mole calculations in chemistry.

Q: What is the difference between molecular weight and atomic weight?

A: The atomic weight of an element is the average weight of a single atom of that element, while the molecular weight of a compound is the sum of the atomic weights of all the atoms present in the compound.

Q: How do I calculate the molecular weight of a compound?

A: To calculate the molecular weight of a compound, you need to sum the atomic weights of all the atoms present in the compound. For example, the molecular weight of water (H2O) is calculated as follows:

Molecular weight of H2O = 2(1.01) + 16.00 = 2.02 + 16.00 = 18.02 g/mol

Q: What is Avogadro's number?

A: Avogadro's number is a constant that represents the number of molecules present in one mole of a substance. It is equal to 6.022 x 10^23 molecules per mole.

Q: How do I convert the number of molecules to the number of grams and vice versa?

A: To convert the number of molecules to the number of grams, you need to multiply the number of molecules by the molecular weight of the compound. To convert the number of grams to the number of molecules, you need to divide the number of grams by the molecular weight of the compound.

Q: What is the significance of Avogadro's number in chemistry?

A: Avogadro's number is a fundamental constant in chemistry that allows us to convert the number of molecules to the number of grams and vice versa. It is used to calculate the number of moles of a substance, which is a measure of the amount of substance present.

Q: How do I calculate the number of moles of a substance?

A: To calculate the number of moles of a substance, you need to divide the number of grams of the substance by its molecular weight. For example, if you have 10 grams of water (H2O), the number of moles of water can be calculated as follows:

Number of moles = Mass of the substance / Molecular weight = 10 g / 18.02 g/mol = 0.555 mol

Q: What is the difference between a mole and a gram?

A: A mole is a unit of measurement that represents 6.022 x 10^23 particles (atoms or molecules), while a gram is a unit of mass. One mole of a substance has a mass equal to its molecular weight.

Q: How do I calculate the mass of a substance in grams?

A: To calculate the mass of a substance in grams, you need to multiply the number of moles of the substance by its molecular weight. For example, if you have 0.555 moles of water (H2O), the mass of water can be calculated as follows:

Mass of the substance = Number of moles $\times$ Molecular weight = 0.555 mol $\times$ 18.02 g/mol = 10 g

Q: What are some common applications of molecular weight and mole calculations?

A: Molecular weight and mole calculations have numerous applications in chemistry, including:

• Calculating the number of moles of a substance
• Determining the mass of a substance in grams
• Calculating the number of molecules present in a given mass
• Determining the molecular weight of a compound
• Calculating the number of moles of a substance present in a given mass

Conclusion

In this article, we have addressed some of the most frequently asked questions on molecular weight and mole calculations in chemistry. We have discussed the significance of Avogadro's number, the difference between molecular weight and atomic weight, and how to calculate the molecular weight of a compound. We have also provided examples of how to convert the number of molecules to the number of grams and vice versa, and how to calculate the number of moles of a substance.

References

• CRC Handbook of Chemistry and Physics, 97th Edition
• Atkins, P. W., & De Paula, J. (2010). Physical Chemistry. Oxford University Press.
• Chang, R. (2010). Chemistry. McGraw-Hill.

Further Reading

• Molecular Weight and Mole Calculations in Chemistry
• Avogadro's Number and the Mole
• Atomic Weights and the Periodic Table