Chapter 3 Flashcards

1
Q

Define chemical Stoichiometry

A

Area of study where the quantities if materials consumed and produced in chemical reactions are considered

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2
Q

If you know the __ __ of objects, the objects behave as they were all __

A

Average mass; Identical

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3
Q

To count atoms, determine the # of __ in a sample by finding its __

A

Atoms; Mass

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4
Q

Modern system of atomic masses is based in __ as the standard

A

12C

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5
Q

__ is assigned a mass of exactly __ atomic mass units (amu)

A

12C; 12

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6
Q

Define mass spectrometer

A

An instrument used to determine the relative masses of atoms or the isotopic composition of a natural element by the deflection of their ions on a magnetic field

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7
Q

Accelerating ions produce own __ __, interacts with applied __ __, which tends to change the path of the __ (most massive __ are deflected the __ & separate)

A

Magnetic field; Magnetic field; Ion; Ions; Least

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8
Q

Masses of atoms are called __ __; atomic mass of _ is an average value of isotopes

A

Atomic weight; C

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9
Q

Define mole

A

Number equal to the number of carbon atoms in exactly 12 grams of pure 12C

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10
Q

Define average atomic mass

A

Average mass of an element

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11
Q

Define molar mass (molecular weight)

A

Mass in grams of one mole of the compound

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12
Q

Define Avogadro’a number

A

6.022 • 10^23; number of units of a substance in one mole of it

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13
Q

Mass of 1 mole of an element is equal to its __ __ in __; 6.022 • 10^23 __ = 1 _

A

Atomic mass; Grams; Amu; g

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14
Q

To find the molar mass, sum the masses of the __ __

A

Component atoms

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15
Q

2 common ways to describe the composition of atoms

A

of atomsPercentage of elements

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16
Q

Define mass percent (weight percent)

A

Percent by mass of a given element in a compound ((mass of element in 1 mole of compound / total mass of 1 mole of compound) x 100)

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17
Q

To determine the formula of a compound, most often a __ sample of the compound is either __ into its component elements or __ with oxygen to produce substances that are than __ and __

A

Weighed; Decomposed; Reacted; Collected; Weighed

18
Q

Since the formula of a compound indicates the number of __ in the compound, masses of the elements must be converted to number of __ (easiest way is to use __ g)

A

Atoms; Atoms; 100.00

19
Q

Numbers very close to whole numbers should be rounded to __ numbers for the integers

A

Whole

20
Q

Define empirical formula

A

Simplest whole number ratio of atoms in a compound

21
Q

Define molecular formula

A

Exact formula of a molecule, giving types of atoms and the number of each type

22
Q

Molecular formula determination method 1 (4)

A

1) Obtain empirical formula2) compute the mass corresponding to the empirical formula 3) calculate the ratio (molar mass / empirical formula mass) 4) multiply the empirical formula by this integer to get the molecular formula

23
Q

Empirical formula determination (4)

A

1) base calculations in 100g, each percent will then represent the mass in grams of that element2) determine number of moles of each element present in 100g of compound using atomic masses 3) divide each value of number of moles by the smallest values 4) multiply each number by an integer so the results are whole numbers

24
Q

Define chemical equation

A

A representation of a chemical reaction showing the relative numbers of reactant and product molecules, and the nature of the reactants

25
Q

Molecular formula determination method 2 (3)

A

1) Using mass %s and the molar mass, determine the mass of each element present in one mole of compound 2) determine the # of moles of each element present in one mole of compound 3) integers represent subscripts in the molecular formula

26
Q

Define reactants

A

Starting substance in a chemical reaction; on left side of chemical equation

27
Q

Chemical equations give the __ __ of the reactants and products

A

Physical states

28
Q

Define products

A

Substance resulting from a chemical reaction; on right side of chemical equation

29
Q

Define balancing a chemical equation

A

Making sure atoms are neither created not destroyed and all atoms present in the reactants must be accounted for among the products

30
Q

Numbers if reactants & products are indicated by the __

A

Coefficients

31
Q

Writing and balancing equations (3)

A

1) Determine reaction occurring (reactants, products, physical states) 2) write the unbalanced equation 3) balance the equation by starting with the most complicated molecules, determine coefficients necessary so the same number of each type of atom appears in both reactant and product sides, do not change formula of any compound

32
Q

Define mole ratio

A

Ratio of moles of a substance to moles of another substance in balanced equations

33
Q

Define haber process

A

The manufacture of ammonia from nitrogen & hydrogen, carried out at high pressure & high temperature with the aid of a catalyst

34
Q

Calculating masses of reactants and products in chemical reactions (5)

A

1) balance equation2) convert known mass of reactant or product to moles of that substance 3) use balanced equation to set up mole ratios4) use mole ratios to calculate number of moles of desired reactant or product 5) convert from moles back to grams if necessary

35
Q

Define Stoichiometric quantities

A

Quantities of reactants mixed in exactly the correct amounts so that all are used up at the same time

36
Q

Always determine which reactant is __ to correctly calculate amounts of product form

A

Limiting

37
Q

Define limiting reactant (limiting reagent)

A

Reactant that is completely consumed when a reaction is run to completion, and limits the amount of products that can be formed

38
Q

Define theoretical yield

A

The maximum amount of a given product that can be formed when the limiting reactant is completely consumed

39
Q

Define percent yield

A

Actual yield of a product as a percentage of the theoretical yield

40
Q

Solving a Stoichiometry problem involving masses of reactants & products (5)

A

1) write & balance the equation for the reaction2) convert the known masses of substances to moles3) determine which reactant is limiting4) using the amount of the limiting reactant and the appropriate mole ratios, compute the number of moles of the desired product 5) convert from moles to grams, using the molar mass

41
Q

Percent yield = (__ yield in g / __ yield in g) x 100%

A

Actual; Theoretical

42
Q

Percent yield can indicate the __ of a particular __ or __ reaction

A

Efficiency; Laboratory; Industrial