PHY-102 Chemistry Exercises essay

PHY-102:Chemistry Exercises

Completethe following exercises.

1. Which of the following are physical properties? (Select all that apply)

1. Color

2. Hardness

3. Density

4. Flammability

5. Conductivity

6. Reactivity with other materials

2. Which of the following describe a physical change? (Select all that apply)

1. Photosynthesis

2. Evaporation of alcohol when a table is wiped with an alcohol swab

3. Burning of firewood

4. Rusting of iron

5. Breaking a glass

6. Melting ice

3. Which of the following are chemical properties? (Select all that apply)

1. Texture

2. Toxicity

3. Conductivity

4. Density

5. Flammability

6. Reactivity with other materials

4. Which of the following describe a chemical change? (Select all that apply)

1. Melting of ice

2. Evaporation of alcohol when a table is wiped with an alcohol swab

3. Burning of firewood

4. Rusting of iron

5. Breaking a glass

6. Cooking an egg

5. Match the following substances with the best classification:

1. Magnesium: element

2. Salt water: solution

3. Blood: Suspension

4. Carbon dioxide: compound

1. Soil sample: Heterogeneous mixture

2. Compound

3. Element

4. Solution

5. Heterogeneous mixture

6. Suspension

6. Which of the following illustrations best illustrate an element, a compound, and a mixture. Provide an explanation for your choices.

.

A:Compound(there is a bond between the atoms)

B:Mixture(mixture of element and compound)

C:Element(these are molecules of an element)

7. Describe a method to separate the substances in a solution.

Distillation:Thismethod is used to separate solutions that have different boilingpoints. The solution is heated in a gradual manner and the substancethat has a lower boiling point/vaporizes the easiest will separatefirst

8. Distinguish between a saturated and an unsaturated solution.

Asaturated solution cannot dissolve any more solute whereasunsaturated solution can still dissolve more solute

9. Match the following:

1. Sodium chloride, NaCl: ionic compund

2. Oxygen, O₂: diatomic gas

3. Methane, CH₄: covalent compound

4. Lithium :element

5. Air: solution

1. Element

2. Solution

3. Diatomic gas

4. Ionic compound

5. Covalent compound

10. Electron dot diagrams are a way to illustrate the number of valence electrons for an element. The symbol for the element is surrounded by a dot for each valence electron. Match the following electron dot diagrams with an element:

1. Electron dot diagram #1:F

2. Electron dot diagram #2: N

3. Electron dot diagram #3: Al

4. Electron dot diagram #4: Na

1. Sodium, Na

2. Aluminum, Al

3. Flourine, F

4. Nitrogen, N

11. For the following questions consider a compound of calcium and chlorine.

1. What type of bond do calcium and chlorine form? Ionic bond

2. Describe how this bond forms.valence electrons of chlorine are transferred to the calcium ion chlrine atom becomes positively charged whreas calcium atom become negatively charged

3. What is the chemical formula for the compound? Explain CaCl₂ (Calcium- Ca2+ Chlorine – Cl- so they form CaCl₂)

12. For the following questions consider a water molecule, H₂O.

1. What type of bond is formed between the oxygen and the hydrogen atoms? Hydrogen bonds

2. Describe how these bonds form. It is formed when a charged part of a molecule, which has a polar covalent bond, create an electrostatic bond/interaction with a substance that has opposite charge

3. Explain why there are two hydrogen atoms for each oxygen atom ( this is because we have H⁺ and O^2- so for them to combine chemically to form a neutral molecule we need 2H⁺ and 1O^2- )

13. For the following questions consider a piece of copper wire.

1. What type of bond is formed between the copper atoms? Metallic bond

2. Describe how these bonds form. It is formed between metals ad it involve the sharing of delocalized electrons amongst a lattice of positive ions

3. Explain why copper is a good electrical conductor. It has delocalized electrons that allow chain reaction of electrons

14. Explain why food stays fresh longer when kept in the refrigerator. The cold present in the fridge slows down the growth of bacteria, which breed, feed, and grow on food, hence, food stays longer

15. In the stratospheric level of the atmosphere there is a high level of ozone, O₃. This ozone absorbs much of the ultraviolet light from the sun and thus protects life in the surface of the Earth from harmful high level of ultraviolet radiation. Explain why one chlorofluorocarbon (CFC) molecule in the ozone layer is capable of breaking down hundreds and even thousands of ozone molecules? The chlorine atom present in CFC is a photocatalyst and it can be used over and over again to destroy the ozone molecule

16. Balance the following chemical reaction by placing the proper coefficients in front of each reactant and in front of the product.

1. What is the coefficient on line (a)? 4

2. What is the coefficient on line (b)? 3

3. What is the coefficient on line (c)? 2

17. Acetylene gas (C₂H₂) burns in the oxyacetylene torch for welding. Balance the chemical reaction by placing the proper coefficients in front of each reactant and each product.

1. What is the coefficient on line (a)? 2

2. What is the coefficient on line (b)? 5

3. What is the coefficient on line (c)? 4

4. What is the coefficient on line (c)? 2

Theremaining questions are multiple-choice questions:

18. What is a substance made up of only one type of atom called?

1. An element

2. A mixture

3. A solution

4. A compound

5. A nucleus

19. Which of the following is a solution?

1. Table salt

2. Nitrogen

3. A vinegar and oil salad dressing

4. Copper wire

5. A 14 karat gold ring

20. Which of the following is a heterogeneous mixture?

1. Table salt

2. Air

3. A vinegar and oil salad dressing

4. Steel

5. A 14 karat gold ring

21. On a container of chicken broth you notice the instructions to “shake well before serving.” Which of the following best describes the chicken broth?

1. A solution

2. An element

3. A compound

4. A suspension

5. A pure substance

22. The formation of an ionic bond involves:

1. A transfer of electrons

2. A transfer of protons

3. A transfer of neutrons

4. A sharing of electrons

5. A sharing of protons

23. Which of the following is the chemical formula for the ionic compound magnesium nitride?

1. MgN

2. Mg₂N

3. Mg₂N₃

4. Mg₃N₂

5. MgN₂

24. Which of the following is correct about a molecule of carbon trichloride?

1. It has one carbon atom for each chloride atom.

2. It has three chloride atoms for each carbon atom.

3. It has three carbon atoms for each chloride atom.

4. It is a mixture of equal parts carbon and trichloride.

5. It is a solution of carbon in chlorine.

25. What is the term for the substances that undergo a change in a chemical reaction?

    1. Solutions

    2. Products

    3. Solvents

    4. Catalysts

    5. Reactants

26. When methane (CH₄) burns it combines with oxygen and forms carbon dioxide and water. Which of the following is the balanced chemical reaction for the burning of methane?

    1. CH₄ + O₂ → CO₂ + H₂O

    2. 3 CH₄ + 6 O₂ → 3 CO₂ + 6 H₂O

    3. 2 CH₄ + 3 O₂ → CO₂ + 4 H₂O

    4. CH₄ + 3 O₂ → 2 CO₂ + 2 H₂O

    5. CH₄ + 2 O₂ → CO₂ + 2 H₂O

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