Chemistry Stoichiometry Problems

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Questions and Answers

What is Hess's Law related to?

The enthalpy change of a reaction (correct)

The atomic number of an element

The heat of formation of a compound

The mass of a compound

What is unique to every compound?

Its heat of formation

Its atomic number

Its own heat of formation (correct)

Its enthalpy change

What does the heat of formation of a compound represent?

The energy required to melt a compound

The energy released when a bond is formed

The energy required to break a bond

The energy required to form a compound (correct)

What is the significance of Hess's Law?

It helps in calculating the enthalpy change of a reaction Signup and view all the answers

What is the unit of heat of formation?

kJ/mol Signup and view all the answers

What is the relationship between the enthalpy change of a reaction and the number of steps involved?

The enthalpy change is independent of the number of steps Signup and view all the answers

What is the probable decay process of 234 into 230?

Alpha emission Signup and view all the answers

What is the resulting element when Uranium (92) decays into?

Thorium Signup and view all the answers

What type of reaction occurs in an electrolytic cell?

Redox reaction Signup and view all the answers

What is true about light elements with even numbers of protons and neutrons?

They are always stable Signup and view all the answers

What is the atomic number of Uranium?

92 Signup and view all the answers

What is the charge of the Zn ion in the reaction?

2+ Signup and view all the answers

What is the atomic number of Thorium?

90 Signup and view all the answers

What happens to the Zn atom during the reaction?

It gets smaller Signup and view all the answers

What is the type of radiation emitted when a nucleus emits a positron?

Beta radiation Signup and view all the answers

What is the role of atom C in the reaction?

It pulls electrons to itself Signup and view all the answers

What is the symbol of the element with atomic number 4?

He Signup and view all the answers

What is the result of the reaction on the Cu atom?

It gets bigger Signup and view all the answers

What is the direction of electron flow in the reaction?

From C to D Signup and view all the answers

What is the lecture topic of the given content?

Chemistry for Engineering Signup and view all the answers

What is the purpose of a bomb calorimeter?

To measure the heat emitted by a sample under controlled conditions Signup and view all the answers

What happens to energy during energy transfer or transformation?

Some energy is lost as heat Signup and view all the answers

What is the result of energy loss as heat?

An increase in entropy Signup and view all the answers

What is the context in which the heat emitted by a sample is measured?

Under controlled conditions Signup and view all the answers

What is the study of the relationships between heat, work, and energy?

Thermodynamics Signup and view all the answers

What is the lecture series about?

Chemistry for Engineering Signup and view all the answers

What is the half-life of Iodine-131?

8 days Signup and view all the answers

How many grams of Iodine-131 will remain after 16 days if you start with 200 grams?

100 grams Signup and view all the answers

What type of decay is K-42 related to?

Beta decay Signup and view all the answers

What is the result of 2 half-lives of Iodine-131 decay?

25 grams remaining Signup and view all the answers

What is the purpose of a decay equation?

To make a radioactive isotope stable Signup and view all the answers

How many half-lives are required for 200 grams of Iodine-131 to decay to 25 grams?

3 half-lives Signup and view all the answers

What is the result of 4 half-lives of Iodine-131 decay?

3.125 grams remaining Signup and view all the answers

How long will it take for 200 grams of Iodine-131 to decay to 12.5 grams?

32 days Signup and view all the answers

Study Notes

Heat Formation and Bomb Calorimeter

Every compound has its own heat of formation
A bomb calorimeter is used to measure the heat emitted by a sample burned under controlled conditions

Hess's Law

States that the enthalpy change of a reaction is the same, regardless of whether it occurs in one step or a series of steps
Energy transfer or transformation leads to an overall increase in entropy, with some energy lost as heat

Redox Reaction and Electrolytic Cells

Example of a redox reaction: Zn (2+) will be an ion, while Cu will be neutral
Zn gradually deteriorates, while Cu grows larger during the reaction

Radioactive Decay

234U decays via alpha emission, then positron decay
If the number of protons and neutrons in light elements are even, they are stable
Heavy elements (83 and above) are unstable and undergo radioactive decay
Intermediate elements (21-82) are also unstable

Half-Life of Iodine-131

Iodine-131 has a half-life of 8 days
If there are 200 grams of Iodine-131, after 32 days, 25 grams will remain

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Description

Solve problems related to stoichiometry, Hess's law, and chemical reactions. Practice calculating molar masses and quantities in chemical reactions.