Chemical Quantities
What are moles in chemistry
A mole is a unit used to count particles such as atoms, molecules, or ions just like a "dozen" is used to count 12 items. But a mole refers to a much larger number:
What is stoichiometry and why is it important?
Stoichiometry is the area of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction.
What is thermochemistry?
Thermochemistry is the study of heat energy changes that happen during chemical reactions or physical changes.
What is an acid?
An acid is a substance that releases hydrogen ions (H⁺) in a solution.
What is nuclear chemistry?
Nuclear chemistry is the study of changes in the nucleus of an atom, especially those involving radioactive decay, fission, and fusion.
What is mole conversion?
Mole conversion is the process of changing between different units related to the mole, such as:
How do I calculate the amount of product from a given amount of reactant?
35.66 grams of water will be produced from 4 grams of hydrogen gas, assuming there is enough oxygen.
What is an exothermic reaction?
An exothermic reaction releases heat to the surroundings.
Ex: Burning of wood or fuel
What is a base?
A base is a substance that releases hydroxide ions (OH⁻) in a solution.
Which type of radiation is the most penetrating?
Gamma (γ) rays – they can pass through most materials and require thick lead or concrete to stop.
What is stoichiometry, and how is it used in chemical reactions?
Stoichiometry is the calculation of reactants and products in a chemical reaction. It involves using the coefficients from the balanced chemical equation to relate amounts of substances involved in the reaction.
How many grams of carbon dioxide (CO₂) are produced when 5.00 grams of glucose (C₆H₁₂O₆) are completely combusted?
Find the molar mass of glucose (C₆H₁₂O₆):
Carbon (C) = 12 g/mol, Hydrogen (H) = 1 g/mol, Oxygen (O) = 16 g/mol
Molar mass of glucose = (6 × 12) + (12 × 1) + (6 × 16) = 180 g/mol
Convert grams of glucose to moles:
Moles of glucose = 5.00 g180 g/mol=0.0278 moles\frac{5.00 \text{ g}}{180 \text{ g/mol}} = 0.0278 \text{ moles}180 g/mol5.00 g=0.0278 moles
Use the mole ratio from the balanced equation:
From the equation, the mole ratio of glucose to CO₂ is 1:6. Therefore:
Convert moles of CO₂ to grams:
Molar mass of CO₂ = (12 × 1) + (16 × 2) = 44 g/mol
Grams of CO₂ = 0.1668 moles×44 g/mol=7.34 g0.1668 \text{ moles} \times 44 \text{ g/mol} = 7.34 \text{ g}0.1668 moles×44 g/mol=7.34 g
So, 5.00 grams of glucose will produce 7.34 grams of CO₂.
What is the formula to calculate heat energy?
q=mcΔT
What happens when an acid reacts with a base? What is the name of this reaction?
An acid + base → salt + water
This is called a neutralization reaction.
If a radioactive isotope has a half-life of 5 years, how much of a 100 g sample is left after 10 years?
25 g
How do you calculate the percent composition of a compound?
To find the percent composition of each element in a compound, you use the formula:
2K+2H2O→2KOH+H2
How many moles of KOH from 3.0 mol of K?
1:1 mole ratio (2K → 2KOH), so :
3.0 mol K → 3.0 mol KOH
How do you know if a reaction is exothermic or endothermic from the temperature change?
If the temperature of the surroundings increases, it’s exothermic.
If the temperature of the surroundings decreases, it’s endothermic.
What is the pH scale?
The pH scale measures how acidic or basic a substance is, from 0 to 14:
Why do atoms undergo radioactive decay?
To become more stable by releasing excess energy or particles.
What is the ideal gas law, and how is it used?
The ideal gas law relates the pressure, volume, temperature, and number of moles of a gas.
How many grams of H₂O from 16.0 g CH₄?
CH4+2O2→CO2+2H2OCH_4 + 2O_2 \rightarrow CO_2 + 2H_2OCH4+2O2→CO2+2H2O
2mol×18=36.0gH2O
What happens to bonds during chemical reactions that involve heat?
Breaking bonds requires energy (endothermic).
Forming bonds releases energy (exothermic).
Name two common household acids and two bases.
Vinegar (contains acetic acid)
Lemon juice (contains citric acid)
Bases:
Baking soda (contains sodium bicarbonate)
Soap (often contains sodium hydroxide or other bases)
What happens to the atomic number during alpha decay?
It decreases by 2, because 2 protons are lost.