A: Chemistry = Chemical Changes 1.5 Calculating Concentration Flashcards

1
Q

What is used to determine the relative concentrations of solutions?

A

Qualitative properties

Observing qualitative properties can provide insights into the concentration of solutions.

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2
Q

What is often useful to know about a solution in science and technology?

A

Specific amount of solute dissolved in a solvent

Knowing the exact quantity of solute helps in various calculations and applications.

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3
Q

What are three common ways to express concentrations?

A

Percent by volume, ppm, molarity

These methods allow for different contexts and applications in communicating concentration.

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4
Q

What does % V/V represent?

A

Volume of liquid solute in total volume of solution

This is a common way to express concentration in solutions.

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5
Q

What does ppm stand for?

A

Parts per million

This unit is often used for very dilute aqueous solutions.

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6
Q

What does molarity express?

A

Amount of moles of a pure substance in total volume of solution

Molarity is a key concept in chemistry for expressing concentration.

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7
Q

Fill in the blank: Manufacturers of consumer products use _______ to communicate concentration.

A

Percent by volume

This is commonly used in product labeling.

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8
Q

Who uses ppm to communicate concentration levels?

A

Agencies that set health and safety standards

Ppm is crucial for monitoring pollutants and health safety.

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9
Q

True or False: Scientists and lab technicians primarily use molarity to communicate concentration.

A

True

Molarity is essential for chemical reactions and laboratory work.

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10
Q

What is the formula for calculating % V/V?

A

mL of solute / mL of solution x 100%

This formula helps in determining the concentration of a solute in a solution.

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11
Q

What is the formula for calculating ppm?

A

g of solute / g of solution x 10^6

This formula is particularly useful for expressing very low concentrations.

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12
Q

What is the formula for calculating molarity?

A

mol of solute / L of solution

Molarity is a standard way to express concentration in chemistry.

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13
Q

What is a mole?

A

A specific amount of a substance that consists of 6.022 x 10^23 particles

This constant is known as Avogadro’s number.

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14
Q

Define molar concentration.

A

The amount of solute, in moles, per litre of solution

Molar concentration is commonly referred to as molarity.

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15
Q

How many hydrogen molecules are produced from breaking down one water molecule?

A

Twice as many hydrogen gas molecules as oxygen gas molecules

This reflects the stoichiometry of the water molecule, H2O.

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16
Q

Why is the mole a useful quantity in chemistry?

A

It enables technologists to combine precise amounts of substances for complete conversion in chemical reactions.

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17
Q

Fill in the blank: The molar concentration of a solution can be calculated using the following relationship: number of moles of _______.

A

[solute]

This relationship is essential for determining the concentration of a solution.

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18
Q

True or False: Molarity is most often used to communicate concentrations within the scientific community.

A

True

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19
Q

What is the most common way to communicate concentrations in the scientific community?

A

Molar concentration or molarity

Molar concentration is widely used in chemistry to express the concentration of a solution.

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20
Q

How can the molar concentration of a solution be calculated?

A

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.

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21
Q

What does the molar concentration communicate?

A

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.

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22
Q

Fill in the blank: The molar concentration of a solution is calculated using the formula C = _______ / V.

A

n

‘n’ represents the number of moles of solute.

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23
Q

True or False: Molar concentration is expressed in units of mol/L.

A

True

Molarity is defined as moles of solute per liter of solution.

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24
Q

What should always be included when recording measurements or doing calculations?

A

Units

Including units ensures clarity and precision in communication.

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25
Q

In Example Problem 1.11, what unit was the volume of the solution given in?

A

Millilitres (mL)

The volume can also be expressed in litres (L) for consistency.

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26
Q

What is a conversion factor?

A

A fraction used to convert one set of units into another

Conversion factors are essential for unit conversion in calculations.

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27
Q

How do conversion factors help in calculations?

A

They keep solutions organized and clarify thinking

Using conversion factors provides a reliable method for handling units.

28
Q

What is sometimes necessary to calculate the molar mass?

A

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.

29
Q

What is the equation for calculating the number of moles in a substance?

A

Mass of the sample / Molar mass

This relationship is fundamental in chemistry for converting mass to moles.

30
Q

What is molar mass?

A

The mass of 1 mol of a substance

Molar mass is typically expressed in grams per mole (g/mol).

31
Q

How do you calculate the number of moles in a substance?

A

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.

32
Q

Fill in the blank: The equation for calculating the number of moles in a substance is _______.

A

mass of the substance (g) / molar mass of the substance (g/mol)

33
Q

True or False: Molar mass is a concept used to determine the number of moles in a substance.

A

True

Molar mass is essential for converting mass to moles.

34
Q

What is the unit for molar mass?

A

grams per mole (g/mol)

Molar mass values depend on the substance’s atomic or molecular weight.

35
Q

What is the first step in calculating molar concentration?

A

Finding the number of moles of the substance

This step is crucial before calculating concentration.

36
Q

What is a standard solution?

A

A solution having a precisely known concentration

Standard solutions are crucial in various fields, especially in health care and manufacturing.

37
Q

Why do industries often prepare their own solutions instead of ordering pre-mixed ones?

A

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.

38
Q

What is the importance of practice and skill in making a standard solution?

A

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.

39
Q

Fill in the blank: A standard solution is essential for allowing precise control of a _______.

A

[chemical reaction]

40
Q

True or False: It is always more expensive to ship pre-mixed solutions than concentrated solutions.

A

True

41
Q

What types of industries require the preparation of standard solutions?

A

Health care and manufacturing

These industries often involve precise chemical reactions and medicinal applications.

42
Q

What is the purpose of diluting chemical solutions?

A

To obtain a solution with a specifically desired concentration

43
Q

What happens to the amount of solute when diluting a solution?

A

The amount of solute is unchanged

44
Q

What changes when a solution is diluted?

A

The amount of solvent changes

45
Q

When solvent is added to a solution, what happens to the number of moles of solute, n?

A

n is unchanged

46
Q

Fill in the blank: In the equation n = CV, what does ‘C’ represent?

A

[concentration]

47
Q

Fill in the blank: In the equation n = CV, what does ‘V’ represent?

A

[volume]

48
Q

True or False: Adding solvent to a solution increases the number of moles of solute.

A

False

49
Q

What is the relationship between solute and solvent when making a solution more concentrated?

A

Water is removed from a solution

50
Q

What are compounds that produce hydrogen ions when dissolved in water called?

A

Acids

Acids form conducting aqueous solutions.

51
Q

Give three examples of slightly acidic foods.

A
  • Soft drinks
  • Tomato sauce
  • Pickles

These foods have a sour taste due to their acid content.

52
Q

What are the potential hazards of concentrated acids?

A
  • Acid burns on skin
  • Blindness if splashed in the eyes
  • Death if swallowed

Concentrated acids are much more dangerous than those found in food.

53
Q

What is the most common acid used in industry?

A

Sulfuric acid

More sulfuric acid is produced each year than any other industrial chemical.

54
Q

What safety precaution should be taken when diluting an acid?

A

Always add the acid to the water in small amounts

This prevents exothermic reactions that can be a safety risk.

55
Q

True or False: Concentrated acids are harmless and safe to handle.

A

False

Concentrated acids can cause severe injuries.

56
Q

Fill in the blank: A substance that produces _______ ions when dissolved in water is called an acid.

A

hydrogen

57
Q

What type of reaction occurs when an acid is diluted?

A

Exothermic

This reaction releases heat, which can pose safety risks.

58
Q

What produces the electric current for a vehicle’s headlights when the motor is shut off?

A

The battery produces the electric current for the lights.

59
Q

What sustains the electric current in a vehicle’s battery?

A

Chemical reactions within the battery sustain the electric current.

60
Q

What decreases in concentration as the battery sustains electric current?

A

The concentration of sulfuric acid decreases.

61
Q

What happens if the concentration of sulfuric acid drops below a critical level?

A

The battery is said to be fully discharged or dead.

62
Q

Fill in the blank: The battery is said to be fully ______ when the sulfuric acid concentration drops below a critical level.

A

[discharged]

63
Q

What produces the electric current for a vehicle’s headlights when the motor is shut off?

A

The battery produces the electric current for the lights.

64
Q

What sustains the electric current in a vehicle’s battery?

A

Chemical reactions within the battery sustain the electric current.

65
Q

What decreases in concentration as the battery sustains electric current?

A

The concentration of sulfuric acid decreases.

66
Q

What happens if the concentration of sulfuric acid drops below a critical level?

A

The battery is said to be fully discharged or dead.

67
Q

Fill in the blank: The battery is said to be fully ______ when the sulfuric acid concentration drops below a critical level.

A

[discharged]