Q: Which of the following is the correct balanced equation for the combustion of methane ($$\text{CH}_4$$)?

$$\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}$$

Q: Which of the following is the correct formula for calculating percent yield?

$$\frac{\text{actual yield}}{\text{theoretical yield}} \times 100\%$$

Question 1

Given the reaction: $$3	ext{Mg}_3(	ext{PO}_4)_2 + 2	ext{Na}_3	ext{PO}_4 ightarrow 4	ext{Ag}_3	ext{PO}_4 + 3	ext{Na}_3	ext{PO}_4$$, how many grams of $$	ext{Ag}_3	ext{PO}_4$$ can be formed from 12.0 grams of $$	ext{Mg}_3(	ext{PO}_4)_2$$ and 15.0 grams of $$	ext{AgNO}_3$$? (Assume excess $$	ext{Na}_3	ext{PO}_4.)$$

Accepted Answer

9.87 grams

Question 2

Which of the following best describes the limiting reagent in a chemical reaction?

Accepted Answer

The reactant that determines the amount of product formed

Question 3

Calculate the mass of $$	ext{CO}_2$$ needed to produce 10,000 L during a complete combustion reaction of methane at STP. ($$1	ext{ mol} = 22.4	ext{ L} at $$STP)

Accepted Answer

19.64 kg

Question 4

Which of the following electron configurations represents a neutral atom of sulfur ($$Z=16$$)?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^4$$

Question 5

Which of the following elements has the highest first ionization energy?

Accepted Answer

Fluorine ($$F)$$

Question 6

Which of the following best explains why atomic radius decreases across a period from left to right?

Accepted Answer

The number of protons increases, pulling electrons closer to the nucleus

Question 7

A sample of gas occupies 4.50 L at 25°C and 1.00 atm. If the gas is heated to 40.0°C and forced into a 3.00 L tank, what is the new pressure? (Assume ideal gas behavior.)

Accepted Answer

2.13 atm

Question 8

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity decreases down a group and increases across a period

Question 9

Which of the following is the correct Lewis structure for $$	ext{CO}_2$$?

Accepted Answer

O=C=O, with each O atom having two lone pairs

Question 10

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electron pairs between atoms

Question 11

Which of the following is NOT a property of ionic compounds?

Accepted Answer

They are malleable and ductile

Question 12

A 3.50 g sample of $$	ext{NaCl} is $$dissolved in 250 mL of water. What is the molarity of the solution? ($$M_{NaCl} = 58.44 	ext{ g/mol})$$

Accepted Answer

0.239 M

Question 13

Which of the following best explains why metals are good conductors of electricity?

Accepted Answer

Metals have loosely held valence electrons that can move freely

Question 14

Which of the following is the correct balanced equation for the combustion of methane ($$	ext{CH}_4$$)?

Accepted Answer

$$	ext{CH}_4 + 2	ext{O}_2 ightarrow 	ext{CO}_2 + 2	ext{H}_2	ext{O}$$

Question 15

Which of the following is a correct application of the ideal gas law?

Accepted Answer

Calculating the number of moles of a gas given its pressure, volume, and temperature

Question 16

Which of the following is the correct formula for calculating percent yield?

Accepted Answer

$$\frac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100\%$$

Question 17

Which of the following best describes the trend in metallic character across a period?

Accepted Answer

Metallic character decreases from left to right

Question 18

Which of the following is a correct statement about the relationship between pressure and volume for a gas at constant temperature (Boyle's Law)?

Accepted Answer

Pressure and volume are inversely proportional

Question 19

How many grams of $$	ext{KClO}_3$$ are needed to form 2.50 L of $$	ext{O}_2 at 0.95 $$atm and 25°C? ($$2	ext{KClO}_3 ightarrow 2	ext{KCl} + 3	ext{O}_2$$; $$R = 0.0821 	ext{ L atm mol}^{-1} 	ext{K}^{-1})$$

Accepted Answer

8.15 grams

CHEM 111 Exam III Review: Stoichiometry, Chemical Reactions, Electrons, Bonding, and Gases

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