Chemistry Worksheet: Mole Concept - Free Printable
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Step-by-step solution for: Chemistry Worksheet: Mole Concept
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Step-by-step solution for: Chemistry Worksheet: Mole Concept
Here's the completed worksheet with explanations for each section and question.
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## Notes Section (Fill in the Blanks)
1. An _isotope_ is an atom that has the same number of protons as other atoms of the same element do but that has a different number of _neutrons_ (and a different atomic mass).
> *Explanation:* Isotopes are variants of an element with the same atomic number (same protons) but different mass numbers due to different neutrons. For example, Carbon-12 and Carbon-14 are isotopes.
2. On the periodic table, the atomic mass displayed is an _average_ of the atomic masses of all of that element’s isotopes.
> *It is a _weighted_ average so the most commonly found _isotopes_ have the most impact on the mass.*
> *Explanation:* The atomic mass shown is not the mass of one isotope, but a weighted average based on how common each isotope is in nature. More abundant isotopes contribute more to the average.
3. A _mole_ is the SI base unit that describes the amount of a substance.
> *_Avogadro’s_ constant is the number of particles in 1 mole of a substance and is equal to 602213670000000000000000 or 6.022 x 10²³.**
> *The _molar mass_ is the mass in grams of 1 mol of a substance.*
> *Explanation:* The mole connects the microscopic world (atoms/molecules) to the macroscopic world (grams). Avogadro’s number (6.022 × 10²³) tells us how many particles are in one mole. Molar mass is numerically equal to atomic/molecular mass in amu, but expressed in g/mol.
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## Questions:
> Answer: 79.90 g/mol
> *Explanation:* From the periodic table, bromine (Br) has an atomic mass of approximately 79.90 amu. Therefore, one mole of Br atoms has a mass of 79.90 grams.
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> Answer: 47.87 g/mol
> *Explanation:* Titanium (Ti) has an atomic mass of about 47.87 amu → molar mass = 47.87 g/mol.
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> Answer: 118.71 g/mol
> *Explanation:* Tin (Sn) has an atomic mass of ~118.71 amu → molar mass = 118.71 g/mol.
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> Answer: 52.00 g/mol
> *Explanation:* Chromium (Cr) has an atomic mass of ~52.00 amu → molar mass = 52.00 g/mol.
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> Answer: 74.92 g
> *Explanation:* 6.02 × 10²³ atoms = 1 mole of atoms. Arsenic (As) has an atomic mass of ~74.92 amu → so 1 mole of As atoms has a mass of 74.92 grams.
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> Answer: 6.022 × 10²³ atoms
> *Explanation:* This is Avogadro’s number, the definition of one mole. It applies to atoms, molecules, ions, etc.
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> Note: This is likely a typo — it should be “Br₂ molecules”, since Br₂ is diatomic.
> Answer: 159.80 g/mol
> *Explanation:* Br₂ means two bromine atoms per molecule.
> - Molar mass of Br = 79.90 g/mol
> - So molar mass of Br₂ = 2 × 79.90 = 159.80 g/mol
> *(If they truly meant "Br₂ atoms", that doesn’t make chemical sense — atoms aren't diatomic; molecules are. But context implies they mean Br₂ molecules.)*
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> Answer: 18.02 g/mol
> *Explanation:* Calculate molar mass:
> - H: 1.008 g/mol × 2 = 2.016 g
> - O: 16.00 g/mol × 1 = 16.00 g
> - Total = 2.016 + 16.00 = 18.016 ≈ 18.02 g/mol
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> Answer: 110.98 g/mol
> *Explanation:*
> - Ca: 40.08 g/mol
> - Cl: 35.45 g/mol × 2 = 70.90 g/mol
> - Total = 40.08 + 70.90 = 110.98 g/mol
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> Answer: 294.18 g/mol
> *Explanation:*
> - K: 39.10 g/mol × 2 = 78.20 g
> - Cr: 52.00 g/mol × 2 = 104.00 g
> - O: 16.00 g/mol × 7 = 112.00 g
> - Total = 78.20 + 104.00 + 112.00 = 294.20 g/mol (often rounded to 294.18 g/mol depending on precision of atomic masses used)
> *(Note: Some tables use K=39.098, Cr=51.996, O=15.999 — then total = 2×39.098 + 2×51.996 + 7×15.999 = 78.196 + 103.992 + 111.993 = 294.181 ≈ 294.18 g/mol)*
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## ✔ Final Answers Summary:
| Question | Answer |
|----------|--------|
| 1 | 79.90 g |
| 2 | 47.87 g |
| 3 | 118.71 g/mol |
| 4 | 52.00 g |
| 5 | 74.92 g |
| 6 | 6.022 × 10²³ atoms |
| 7 | 159.80 g (for Br₂ molecules) |
| 8 | 18.02 g |
| 9 | 110.98 g/mol |
| 10 | 294.18 g/mol |
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Let me know if you’d like this formatted as a printable worksheet or need help with more practice problems!
---
## Notes Section (Fill in the Blanks)
1. An _isotope_ is an atom that has the same number of protons as other atoms of the same element do but that has a different number of _neutrons_ (and a different atomic mass).
> *Explanation:* Isotopes are variants of an element with the same atomic number (same protons) but different mass numbers due to different neutrons. For example, Carbon-12 and Carbon-14 are isotopes.
2. On the periodic table, the atomic mass displayed is an _average_ of the atomic masses of all of that element’s isotopes.
> *It is a _weighted_ average so the most commonly found _isotopes_ have the most impact on the mass.*
> *Explanation:* The atomic mass shown is not the mass of one isotope, but a weighted average based on how common each isotope is in nature. More abundant isotopes contribute more to the average.
3. A _mole_ is the SI base unit that describes the amount of a substance.
> *_Avogadro’s_ constant is the number of particles in 1 mole of a substance and is equal to 602213670000000000000000 or 6.022 x 10²³.**
> *The _molar mass_ is the mass in grams of 1 mol of a substance.*
> *Explanation:* The mole connects the microscopic world (atoms/molecules) to the macroscopic world (grams). Avogadro’s number (6.022 × 10²³) tells us how many particles are in one mole. Molar mass is numerically equal to atomic/molecular mass in amu, but expressed in g/mol.
---
## Questions:
1) What is the mass of one mole of Br atoms?
> Answer: 79.90 g/mol
> *Explanation:* From the periodic table, bromine (Br) has an atomic mass of approximately 79.90 amu. Therefore, one mole of Br atoms has a mass of 79.90 grams.
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2) What is the mass of one mole of titanium atoms?
> Answer: 47.87 g/mol
> *Explanation:* Titanium (Ti) has an atomic mass of about 47.87 amu → molar mass = 47.87 g/mol.
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3) What is the molar mass of tin?
> Answer: 118.71 g/mol
> *Explanation:* Tin (Sn) has an atomic mass of ~118.71 amu → molar mass = 118.71 g/mol.
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4) What is the mass of one mole of chromium atoms?
> Answer: 52.00 g/mol
> *Explanation:* Chromium (Cr) has an atomic mass of ~52.00 amu → molar mass = 52.00 g/mol.
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5) What is the mass of 6.02 x 10²³ atoms of arsenic?
> Answer: 74.92 g
> *Explanation:* 6.02 × 10²³ atoms = 1 mole of atoms. Arsenic (As) has an atomic mass of ~74.92 amu → so 1 mole of As atoms has a mass of 74.92 grams.
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6) How many atoms are there in one mole of atoms?
> Answer: 6.022 × 10²³ atoms
> *Explanation:* This is Avogadro’s number, the definition of one mole. It applies to atoms, molecules, ions, etc.
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7) What is the mass of one mole of Br₂ atoms?
> Note: This is likely a typo — it should be “Br₂ molecules”, since Br₂ is diatomic.
> Answer: 159.80 g/mol
> *Explanation:* Br₂ means two bromine atoms per molecule.
> - Molar mass of Br = 79.90 g/mol
> - So molar mass of Br₂ = 2 × 79.90 = 159.80 g/mol
> *(If they truly meant "Br₂ atoms", that doesn’t make chemical sense — atoms aren't diatomic; molecules are. But context implies they mean Br₂ molecules.)*
---
8) What is the mass of one mole of water (H₂O)?
> Answer: 18.02 g/mol
> *Explanation:* Calculate molar mass:
> - H: 1.008 g/mol × 2 = 2.016 g
> - O: 16.00 g/mol × 1 = 16.00 g
> - Total = 2.016 + 16.00 = 18.016 ≈ 18.02 g/mol
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9) What is the molar mass of CaCl₂?
> Answer: 110.98 g/mol
> *Explanation:*
> - Ca: 40.08 g/mol
> - Cl: 35.45 g/mol × 2 = 70.90 g/mol
> - Total = 40.08 + 70.90 = 110.98 g/mol
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10) What is the molar mass of K₂Cr₂O₇?
> Answer: 294.18 g/mol
> *Explanation:*
> - K: 39.10 g/mol × 2 = 78.20 g
> - Cr: 52.00 g/mol × 2 = 104.00 g
> - O: 16.00 g/mol × 7 = 112.00 g
> - Total = 78.20 + 104.00 + 112.00 = 294.20 g/mol (often rounded to 294.18 g/mol depending on precision of atomic masses used)
> *(Note: Some tables use K=39.098, Cr=51.996, O=15.999 — then total = 2×39.098 + 2×51.996 + 7×15.999 = 78.196 + 103.992 + 111.993 = 294.181 ≈ 294.18 g/mol)*
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## ✔ Final Answers Summary:
| Question | Answer |
|----------|--------|
| 1 | 79.90 g |
| 2 | 47.87 g |
| 3 | 118.71 g/mol |
| 4 | 52.00 g |
| 5 | 74.92 g |
| 6 | 6.022 × 10²³ atoms |
| 7 | 159.80 g (for Br₂ molecules) |
| 8 | 18.02 g |
| 9 | 110.98 g/mol |
| 10 | 294.18 g/mol |
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Let me know if you’d like this formatted as a printable worksheet or need help with more practice problems!
Parent Tip: Review the logic above to help your child master the concept of mole concept worksheet.
