General Chemistry Exam 1 Study Guidance

Q1. Which one of the following compounds is ionic?

Background

Topic: Types of Chemical Bonds

This question tests your understanding of the difference between ionic and covalent compounds.

Key Terms:

• Ionic compound: Formed from the transfer of electrons between a metal and a nonmetal.

• Covalent compound: Formed from the sharing of electrons between nonmetals.

Step-by-Step Guidance

1. Identify which elements in each compound are metals and which are nonmetals.

2. Recall that ionic compounds are typically formed between metals and nonmetals.

3. Examine each option and determine if it fits the criteria for an ionic compound.

Try solving on your own before revealing the answer!

Final Answer: D) CaO

CaO is formed from calcium (a metal) and oxygen (a nonmetal), making it an ionic compound.

Q2. Which of the following is the lowest temperature?

Background

Topic: Temperature Conversions

This question tests your ability to convert between Fahrenheit, Celsius, and Kelvin.

Key Formulas:

• $\text{Celsius to Kelvin: } K = ^\circ C + 273.15$

• $\text{Fahrenheit to Celsius: } ^\circ C = \frac{5}{9}(F - 32)$

Step-by-Step Guidance

1. Convert 54°F to Celsius using $^\circ C = \frac{5}{9}(54 - 32)$.

2. Convert the Celsius value to Kelvin using $K = ^\circ C + 273.15$.

3. Compare the converted values for all options to determine which is lowest.

Try solving on your own before revealing the answer!

Final Answer: A) 54°F

54°F is the lowest temperature after conversion to Kelvin.

Q3. If the melting point of titanium metal is 1672°C, what is its melting point in Kelvin?

Background

Topic: Temperature Conversion

This question tests your ability to convert Celsius to Kelvin.

Key Formula:

• $K = ^\circ C + 273.15$

Step-by-Step Guidance

1. Write down the melting point in Celsius: $1672^\circ C$.

2. Add 273.15 to the Celsius value to convert to Kelvin: $K = 1672 + 273.15$.

Try solving on your own before revealing the answer!

Final Answer: D) 1945 K

Adding 273.15 to 1672 gives the melting point in Kelvin.

Q4. When 10.0 g of calcium metal is reacted with water, 5.00 g of calcium hydroxide is produced. Using the following balanced equation, calculate the percent yield for the reaction?

Ca(s) + 2 H2O(l) → Ca(OH)2(aq) + H2(g)

Background

Topic: Stoichiometry and Percent Yield

This question tests your ability to calculate percent yield from a chemical reaction.

Key Formula:

• $\text{Percent Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100\%$

Step-by-Step Guidance

1. Calculate the moles of calcium used: $\text{moles Ca} = \frac{10.0\,g}{\text{molar mass of Ca}}$.

2. Use the stoichiometry of the reaction to find the theoretical yield of Ca(OH)2.

3. Calculate the percent yield using the actual yield (5.00 g) and the theoretical yield.

Try solving on your own before revealing the answer!

Final Answer: D) 27.1%

The percent yield is calculated using the actual and theoretical yields.

Q5. Calculate the percentage by mass of carbon in CO2.

Background

Topic: Mass Percent Composition

This question tests your ability to calculate the mass percent of an element in a compound.

Key Formula:

• $\text{Mass percent} = \frac{\text{mass of element in 1 mole}}{\text{molar mass of compound}} \times 100\%$

Step-by-Step Guidance

1. Find the molar mass of CO2: $\text{C} = 12.01\,g/mol$, $\text{O} = 16.00\,g/mol$.

2. Calculate the total mass of CO2: $12.01 + 2 \times 16.00$.

3. Calculate the mass percent of carbon: $\frac{12.01}{\text{total mass}} \times 100\%$.

Try solving on your own before revealing the answer!

Final Answer: C) 27.29%

The mass percent is calculated using the molar mass of carbon and CO2.

Q6. Which species below is the carbonate ion?

Background

Topic: Polyatomic Ions

This question tests your knowledge of common polyatomic ions and their formulas.

Key Terms:

• Carbonate ion: $\text{CO}_3^{2-}$

Step-by-Step Guidance

1. Recall the formula for the carbonate ion.

2. Compare the options to identify the correct formula.

Try solving on your own before revealing the answer!

Final Answer: B) CO32-

CO32- is the correct formula for the carbonate ion.

Q7. Osmium has a density of 22.6 g/cm3. What volume (in cm3) would be occupied by a 21.8 g sample of osmium?

Background

Topic: Density Calculations

This question tests your ability to use the density formula to find volume.

Key Formula:

• $\text{Density} = \frac{\text{mass}}{\text{volume}}$

• $\text{Volume} = \frac{\text{mass}}{\text{density}}$

Step-by-Step Guidance

1. Write down the mass and density values: $\text{mass} = 21.8\,g$, $\text{density} = 22.6\,g/cm^3$.

2. Use the formula $\text{Volume} = \frac{\text{mass}}{\text{density}}$ to set up the calculation.

Try solving on your own before revealing the answer!

Final Answer: A) 0.965 cm3

Divide the mass by the density to find the volume.

Q8. Of the reactions below, which one is a decomposition reaction?

Background

Topic: Types of Chemical Reactions

This question tests your ability to identify decomposition reactions.

Key Terms:

• Decomposition reaction: A single compound breaks down into two or more simpler substances.

Step-by-Step Guidance

1. Look for a reaction where one reactant forms two or more products.

2. Compare each option to see which fits the definition of decomposition.

Try solving on your own before revealing the answer!

Final Answer: A) NH4Cl → NH3 + HCl

This reaction shows a single compound breaking into two products.

Q9. When silver nitrate (169.87 g/mol) reacts with barium chloride (208.23 g/mol), silver chloride and barium nitrate are formed. How many grams of silver chloride (143.32 g/mol) are formed when 10.0 g of silver nitrate reacts with 15.0 g of barium chloride?

2 AgNO3 + BaCl2 → 2 AgCl + Ba(NO3)2

Background

Topic: Limiting Reactant and Stoichiometry

This question tests your ability to determine the limiting reactant and calculate the mass of product formed.

Key Steps:

• Calculate moles of each reactant.

• Determine the limiting reactant.

• Use stoichiometry to find moles of AgCl produced.

• Convert moles of AgCl to grams.

Step-by-Step Guidance

1. Calculate moles of AgNO3: $\text{moles AgNO}_3 = \frac{10.0\,g}{169.87\,g/mol}$.

2. Calculate moles of BaCl2: $\text{moles BaCl}_2 = \frac{15.0\,g}{208.23\,g/mol}$.

3. Use the balanced equation to determine which reactant is limiting.

4. Calculate moles of AgCl produced based on the limiting reactant.

Try solving on your own before revealing the answer!

Final Answer: B) 8.44 g

Use the limiting reactant and stoichiometry to find the mass of AgCl produced.

Q10. What is the name of the acid H3PO4?

Background

Topic: Naming Acids

This question tests your knowledge of acid nomenclature.

Key Terms:

• Acid nomenclature: Acids containing polyatomic ions ending in "-ate" are named as "ic acid".

Step-by-Step Guidance

1. Identify the polyatomic ion in H3PO4 (phosphate).

2. Recall the naming rule: "phosphate" becomes "phosphoric acid".

Try solving on your own before revealing the answer!

Final Answer: D) phosphoric acid

H3PO4 is named phosphoric acid because it contains the phosphate ion.