A: Chemistry = Chemical Changes 2.1 Compounds and Chemical Change Flashcards
What is tarnishing in metals?
A chemical reaction evidenced by a color change
Which metal is known to tarnish due to reactions with air molecules?
Silver
What molecules in the air does silver react with to cause tarnishing?
Hydrogen sulfide in the presence of oxygen
What are the products of the tarnishing reaction of silver?
Silver sulfide (Ag2S) and water
What gives tarnished silverware its black color?
Silver sulfide
Fill in the blank: The process of developing a balanced chemical equation is called _______.
[balancing]
What is the first step in writing a balanced chemical equation?
Translate the words into chemical formulas
What is the chemical formula for solid silver?
Ag(s)
What is the chemical formula for hydrogen sulfide gas?
H₂S(g)
What is the chemical formula for oxygen gas?
O₂(g)
What is the chemical formula for solid silver sulfide?
Ag₂S(s)
solid silver + hydrogen sulfide gas + oxygen gas makes solid silver sulfide + liquid water
Fill in the blank: The balanced chemical equation is _______.
4 Ag(s) + 2 H₂S(g) + O₂(g) → 2 Ag₂S(s) + 2 H₂O(l)
What do coefficients of 1 in a balanced chemical equation indicate? Should they be written?
They are not recorded
What do coefficients in a chemical equation ensure?
They ensure that the equation is balanced.
What happens to atoms in a chemical reaction?
Atoms are rearranged; they are not created nor destroyed.
Fill in the blank: Atoms were not created nor destroyed; they were simply _______.
rearranged.
What is the purpose of using a table in chemical equations?
To check whether chemical equations are balanced.
True or False: New compounds in a chemical reaction are formed by creating new atoms.
False.
What does it mean for a chemical equation to be balanced?
The total of each kind of atom before the reaction is equal to the total of each kind of atom after the reaction.
This reflects the law of conservation of matter.
What does the conservation of matter imply in a chemical reaction?
Matter is conserved, meaning it cannot be created or destroyed in a chemical reaction.
What do the coefficients in a balanced equation indicate?
The coefficients indicate the relative amounts of reactants and products in the reaction.
In the reaction of silver with silver sulfide, what is the ratio of silver atoms to silver sulfide units produced?
4-to-2 ratio.
This means for every four atoms of silver, two units of silver sulfide crystal are produced.
Fill in the blank: When silver reacts with silver sulfide, for every _______ atoms of silver, there are only two units of silver sulfide produced.
four
What does it mean for a chemical equation to be balanced?
The total of each kind of atom before the reaction is equal to the total of each kind of atom after the reaction.
This reflects the law of conservation of matter.
What does the conservation of matter imply in a chemical reaction?
Matter is conserved, meaning it cannot be created or destroyed in a chemical reaction.
What charge does a sulfur atom acquire when it fills its outer energy level?
2-
What charge does a silver atom acquire when it loses one electron?
1+
What is the term for the ratio of coefficients in a balanced chemical equation?
Mole ratio
What does a mole ratio indicate in a chemical reaction?
Proportion of substances involved
For example, there will always be double the number of silver atoms to units of silver sulfide.
True or False: Mole ratios can be used to solve problems in chemistry.
True
They are very useful for problem-solving.
Fill in the blank: The coefficient of the required substance is used along with the __________ of the given substance to determine mole ratios.
coefficient
Coefficients are essential for establishing the mole ratio in a reaction.
How can mole ratios be expressed?
As a ratio
Examples include 600 to 300 or 4 mol to 2 mol.
What is the mole ratio of silver to silver sulfide in the balanced chemical equation?
4:2
The balanced chemical equation is O₂(g) + 4 Ag(s) + 2 H₂S(g) → 2 Ag₂S(s) + 2 H₂O(l), indicating that 4 moles of silver are required for every 2 moles of silver sulfide.
How many moles of silver are required to make 0.876 mol of silver sulfide?
1.75 mol
To find the moles of silver required, multiply the moles of silver sulfide by the mole ratio 0.876 mol Ag₂S × 4 mol Ag / 2 mol Ag₂S = 1.75 mol Ag₂S.
Fill in the blank: To determine the amount of silver required to make 0.876 mol of silver sulfide, first determine the _______.
mole ratio
In math this is the conversion factor.
What is the balanced chemical equation for the reaction involving silver and silver sulfide?
O₂(g)+ 4 Ag(s) + 2 H₂S(g) → 2 Ag₂S(s) + 2 H₂O(l)
This equation shows the reactants and products in the synthesis of silver sulfide.
True or False: 0.876 mol of silver sulfide requires 0.876 mol of silver.
False
The correct amount of silver required is 1.75 mol, based on the mole ratio.
What is formed when aluminium metal reacts with oxygen in the air?
Aluminium oxide
The reaction is represented by the equation: 4 Al(s) + 3 O2(g) → 2 Al2O3(s)
How many moles of aluminium oxide are formed from 6.25 moles of aluminium?
3.13 moles
According to the reaction stoichiometry, 4 moles of Al produce 2 moles of Al2O3.
Fill in the blank: To react with 6.25 moles of aluminium, you need _____ moles of oxygen.
4.69 moles
The stoichiometry of the reaction shows that 4 moles of Al react with 3 moles of O2.
If you have 6.25 moles of aluminium, how many moles of oxygen are required?
4.6875 moles
The calculation is based on the 4:3 ratio from the balanced equation.
True or False: 3 moles of oxygen are needed for every 4 moles of aluminium in the reaction.
True
This is a direct reflection of the stoichiometric coefficients in the balanced chemical equation.
What is the significance of the warrior cache described in the lesson?
It represents a rare discovery of well-preserved artifacts in a heavily forested area.
What types of artifacts were found in the warrior cache?
Bone tools and copper artifacts.
What environmental condition typically affects the preservation of artifacts in forested areas?
Acidic soil environment due to decaying forest vegetation.
How does acidic soil impact artifacts?
It results in the rapid deterioration of objects.
What played a role in preserving the artifacts found in the warrior cache?
Layers of shells surrounding the artifacts.
What did the layers of shells represent?
Hundreds of years of debris from the First Nations people.
How did rainwater affect the shells and the surrounding environment?
It dissolved the shells, creating a solution that neutralized the acid.
Fill in the blank: The naturally acidic soil chemistry was altered by the layers of _______.
[shells]
True or False: The warrior cache artifacts were preserved due to the acidic soil environment.
False
What was the main effect of the shell layers on the preservation of artifacts?
Helped prevent further deterioration.
What is the role of chemistry in preserving artifacts?
Chemistry is used by experts to preserve and display valuable artifacts
An understanding of chemical reactions ensures optimal maintenance conditions.
What is one method to prevent damage to artifacts during handling?
Handling artifacts with gloves
This prevents the transfer of sweat and oils from the skin.
What type of materials should be used for packing and shipping artifacts?
Special acid-free tissue and acid-free boxes
These materials help prevent chemical reactions that can damage the artifacts.
Where should artifacts be displayed to ensure their preservation?
In climate-controlled cabinets
This ensures stable temperatures, low humidity, and an environment free of harmful substances.
Fill in the blank: Artifacts should be maintained under _______ conditions.
optimum
True or False: Displaying artifacts in regular cabinets is sufficient for their preservation.
False
Artifacts require climate-controlled environments for proper preservation.
