A: Chemistry = Chemical Changes 1.5 Calculating Concentration Flashcards
What is used to determine the relative concentrations of solutions?
Qualitative properties
Observing qualitative properties can provide insights into the concentration of solutions.
What is often useful to know about a solution in science and technology?
Specific amount of solute dissolved in a solvent
Knowing the exact quantity of solute helps in various calculations and applications.
What are three common ways to express concentrations?
Percent by volume, ppm, molarity
These methods allow for different contexts and applications in communicating concentration.
What does % V/V represent?
Volume of liquid solute in total volume of solution
This is a common way to express concentration in solutions.
What does ppm stand for?
Parts per million
This unit is often used for very dilute aqueous solutions.
What does molarity express?
Amount of moles of a pure substance in total volume of solution
Molarity is a key concept in chemistry for expressing concentration.
Fill in the blank: Manufacturers of consumer products use _______ to communicate concentration.
Percent by volume
This is commonly used in product labeling.
Who uses ppm to communicate concentration levels?
Agencies that set health and safety standards
Ppm is crucial for monitoring pollutants and health safety.
True or False: Scientists and lab technicians primarily use molarity to communicate concentration.
True
Molarity is essential for chemical reactions and laboratory work.
What is the formula for calculating % V/V?
mL of solute / mL of solution x 100%
This formula helps in determining the concentration of a solute in a solution.
What is the formula for calculating ppm?
(g of solute / g of solution) x 10^6
This formula is particularly useful for expressing very low concentrations.
What is the formula for calculating molarity?
mol of solute / L of solution
Molarity is a standard way to express concentration in chemistry.
What is a mole?
A specific amount of a substance that consists of 6.022 x 10^23 particles
This constant is known as Avogadro’s number.
Define molar concentration.
The amount of solute, in moles, per litre of solution
Molar concentration is commonly referred to as molarity.
How many hydrogen molecules are produced from breaking down one water molecule?
Twice as many hydrogen gas molecules as oxygen gas molecules
This reflects the stoichiometry of the water molecule, H2O.
Why is the mole a useful quantity in chemistry?
It enables technologists to combine precise amounts of substances for complete conversion in chemical reactions.
Fill in the blank: The molar concentration of a solution can be calculated using the following relationship: number of moles of _______.
[solute compared to solution]
This relationship is essential for determining the concentration of a solution.
True or False: Molarity is most often used to communicate concentrations within the scientific community.
True
What is the most common way to communicate concentrations in the scientific community?
Molar concentration or molarity
Molar concentration is widely used in chemistry to express the concentration of a solution.
How can the molar concentration of a solution be calculated?
C = (Number of moles of solute) / (Total volume of the solution)
This formula helps in determining the concentration of solute in a given volume of solution.
What does the molar concentration communicate?
The number of molecules or ions of solute dissolved or dissociated in a specified volume of a solution
This is crucial for understanding the properties and behavior of the solution.
Fill in the blank: The molar concentration of a solution is calculated using the formula C = _______ / V.
n
‘n’ represents the number of moles of solute.
True or False: Molar concentration is expressed in units of mol/L.
True
Molarity is defined as moles of solute per liter of solution.
What should always be included when recording measurements or doing calculations?
Units
Including units ensures clarity and precision in communication.
What is a conversion factor?
A fraction used to convert one set of units into another
Conversion factors are essential for unit conversion in calculations.
How do conversion factors help in calculations?
They keep solutions organized and clarify thinking
Using conversion factors provides a reliable method for handling units.
What is sometimes necessary to calculate the molar mass?
Calculate the number of moles using the mass of the sample and information from the periodic table
This calculation is crucial for stoichiometric calculations in chemistry.
The characteristic molar mass of an element is simply the atomic mass in g/mol. However, molar mass can also be calculated by multiplying the atomic mass in amu by the molar mass constant (1 g/mol). To calculate the molar mass of a compound with multiple atoms, sum all the atomic mass of the constituent atoms.
What is the equation for calculating the number of moles in a substance?
Mass of the sample / Molar mass
This relationship is fundamental in chemistry for converting mass to moles.
n = m / M
mol = g / (g / mol)
Molar mass is simply atomic mass from the periodic table.
Mass is the amount in your experiment.
What is molar mass?
The mass of 1 mol of a substance
Molar mass is typically expressed in grams per mole (g/mol).
This can be found directly on the periodic table.
How do you calculate the number of moles in a substance?
Number of moles = mass of the substance (g) / molar mass of the substance (g/mol)
This formula allows for the calculation of the moles based on the mass and molar mass.
Fill in the blank: The equation for calculating the number of moles in a substance is _______.
mass of the substance (g) / molar mass of the substance (g/mol)
True or False: Molar mass is a concept used to determine the number of moles in a substance.
True
Molar mass is essential for converting mass to moles.
What is the unit for molar mass?
grams per mole (g/mol)
Molar mass values depend on the substance’s atomic or molecular weight.
What is the first step in calculating molar concentration?
Finding the number of moles of the substance
This step is crucial before calculating concentration.
What is a standard solution?
A solution having a precisely known concentration
Standard solutions are crucial in various fields, especially in health care and manufacturing.
Why do industries often prepare their own solutions instead of ordering pre-mixed ones?
It is less expensive to ship highly concentrated solutions and sometimes solutions need to be modified
This modification allows for greater flexibility in mixing specific solutions for specific situations.
What is the importance of practice and skill in making a standard solution?
The slightest error can cause the concentration of your standard solution to be less accurate
Accurate concentrations are essential for precise control of chemical reactions.
Fill in the blank: A standard solution is essential for allowing precise control of a _______.
[chemical reaction]
True or False: It is always more expensive to ship pre-mixed solutions than concentrated solutions.
True
What types of industries require the preparation of standard solutions?
Health care and manufacturing
These industries often involve precise chemical reactions and medicinal applications.
What is the purpose of diluting chemical solutions?
To obtain a solution with a specifically desired concentration
What happens to the amount of solute when diluting a solution?
The amount of solute is unchanged
What changes when a solution is diluted?
The amount of solvent changes
When solvent is added to a solution, what happens to the number of moles of solute, n?
n is unchanged
Fill in the blank: In the equation n = CV, what does ‘C’ represent?
[concentration]
Fill in the blank: In the equation n = CV, what does ‘V’ represent?
[volume]
True or False: Adding solvent to a solution increases the number of moles of solute.
False
What is the relationship between solute and solvent when making a solution more concentrated?
Water is removed from a solution
What are compounds that produce hydrogen ions when dissolved in water called?
Acids
Acids form conducting aqueous solutions.
Give three examples of slightly acidic foods.
- Soft drinks
- Tomato sauce
- Pickles
These foods have a sour taste due to their acid content.
What are the potential hazards of concentrated acids?
- Acid burns on skin
- Blindness if splashed in the eyes
- Death if swallowed
Concentrated acids are much more dangerous than those found in food.
What is the most common acid used in industry?
Sulfuric acid
More sulfuric acid is produced each year than any other industrial chemical.
What safety precaution should be taken when diluting an acid?
Always add the acid to the water in small amounts
This prevents exothermic reactions that can be a safety risk.
True or False: Concentrated acids are harmless and safe to handle.
False
Concentrated acids can cause severe injuries.
Fill in the blank: A substance that produces _______ ions when dissolved in water is called an acid.
hydrogen
What type of reaction occurs when an acid is diluted?
Exothermic
This reaction releases heat, which can pose safety risks.
What produces the electric current for a vehicle’s headlights when the motor is shut off?
The battery produces the electric current for the lights.
What sustains the electric current in a vehicle’s battery?
Chemical reactions within the battery sustain the electric current.
What decreases in concentration as the battery sustains electric current?
The concentration of sulfuric acid decreases.
What happens if the concentration of sulfuric acid drops below a critical level?
The battery is said to be fully discharged or dead.
Fill in the blank: The battery is said to be fully ______ when the sulfuric acid concentration drops below a critical level.
[discharged]
