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Honors Chemistry > Module 7 Test > Flashcards

Module 7 Test Flashcards

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1
Q

What is Avogadro’s number equal to?

A

6.022 x 1023 units/mol

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2
Q

A mole is defined by?

A

The number of atoms in the exact amount of a unit

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3
Q

A unit can be what?

A

Atoms, molecules, ions

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4
Q

What do you use as a conversion factor when asked “how many molecules are in a ____ # of moles?

A

Avogadro’s number

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5
Q

Do you use Avogadro’s number directly to convert from grams?

A

No

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6
Q

What do you use to convert from grams if you don’t use Avogadro’s number?

A

The Mole Island chart

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7
Q

The molar mass of the compound is equal to what?

A

The molar mass of a compound is equal to the molar mass of the all the elements that it is composed of

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8
Q

What does the chemical formula tell you?

A

It tells you how many/much of each element is in the compound

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9
Q

What are the units for molar mass?

A

The units are g/mol

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10
Q

What is the formula unit?

A

The simplest ratio of cations to anions

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11
Q

What can molar mass be used for?

A

Can be used to convert the amount of a substance from moles to mass, or mass to moles

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12
Q

Why is percent composition useful for scientists?

A

Percent composition helps them determine the specific elements in a compound and the ratios of the elements in the compound

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13
Q

What is percent composition?

A

Percent composition is the percentage by mass of each element in a compound

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14
Q

If you know the composition of a compound, then what else can you do?

A

Then you can determine the percentage composition of the elements that make up the entire compound

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15
Q

What do you do first when finding percent composition?

A

You determine the mass of each element (by the amount of elements present x the atomic mass)

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16
Q

What is the second step for finding percent composition?

A

Calculate the molar mass of the compound (add all the masses of each element together)

17
Q

What is the third step for finding percent composition?

A

Divide the mass of each element by the molar mass them multiply by 100 to get a percentage

18
Q

What is the fourth and last step for finding percent composition?

A

Verify your answers and the percentages should add up to 100%

19
Q

What is the empirical formula?

A

It is the simplest ratio of elements in a compound

20
Q

It is okay if the empirical formula my not always be the right formula for the compound?

A

Yes

21
Q

What is the empirical formula calculated from?

A

The percent composition

22
Q

What is the first step in finding the empirical formula?

A

Convert the percent composition to mass in grams (assume in a 100 g sample)

23
Q

What is the second step in finding the empirical formula?

A

You need to convert the mass to moles by using the atomic mass (divide each element by their own atomic mass)

24
Q

What is the third step in finding the empirical formula?

A

Determine which element has the lowest number of moles

25
Q

What is the fourth step in finding the empirical formula?

A

Set up ratios by dividing all each element by the least amount of moles

26
Q

What do you need to do if each element does not have a full number after you divided by the least amount of moles?

A

You need to multiply all elements by a common number to get the smallest whole number ratio

27
Q

If the number is/ends in .33 what do you multiply by?

A

Multiply by 3

28
Q

If the number is/ends in .25 what do you multiply by?

A

Multiply by 4

29
Q

If the number is/ends in .66 what do you multiply by?

A

Multiply by 3

30
Q

If the number is/ends in .75 what do you multiply by?

A

Multiply by 4

31
Q

If the number is/ends in.5 what do you multiply by?

A

Multiply by 2

32
Q

What is the fifth step in finding the empirical formula?

A

Place the numbers from the ratios as the subscripts of that element in the empirical formula

33
Q

What can empirical formulas be used to determine (in regards to the molecular formula)?

A

Can be used to determine the molecular formula if the molar mass of the compound is known

34
Q

What is the first step in finding the molecular formula?

A

Make sure the empirical formula and the molar mass of the compound is given

35
Q

What is the second step in finding the molecular formula?

A

Calculate the molar mass of the empirical formula

36
Q

What is the third step in finding the molecular formula?

A

Divide the molar mass of the compound by the molar mass of the empirical formula

37
Q

What is the fourth and final step in finding the molecular formula?

A

Multiply all of the subscripts by the ratio (answer) found in the previous step

Honors Chemistry (13 decks)

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