1. מסה מולרית Molar mass is the mass of one mole of a substance.
the number of grams that equals the atomic mass of that element.
Molar mass is rounded to the tenths (0.1 g) place for use in this text.
1 mole Ag mole C mole S
= g = g = g

2. מסה מולרית Molar Mass The molar mass
is the mass of one mole of an element or compound.
is the atomic mass expressed in grams.

3. תרגיל
Learning Check
Give the molar mass of the following elements to the nearest 0.1 g.
1. K = ________
2. Sn = ________
3. Si = ________

4. פתרון
Solution
Give the molar mass of the following elements to the nearest 0.1 g.
1. K = g
2. Sn = g
3. Si = g

5. מסה מולרית של תרכובת +דוגמא 1
The molar mass of a compound is the sum of the molar masses of the elements in the formula.
Example: Calculate the molar mass of CaCl2.
Element
Number of Moles
Atomic Mass
Total Mass Ca 1
40.1 g/mole
40.1 g Cl 2
35.5 g/mole
71.0 g
CaCl2
111.1 g

6. דוגמא 2 לחישוב מסה מולרית של תרכובת Molar Mass of K3PO4
Calculate the molar mass of K3PO4.
Element
Number of Moles
Atomic Mass
Total Mass in K3PO4 K 3
39.1 g/mole
117.3 g P 1
31.0 g/mole
31.0 g O 4
16.0 g/mole
64.0 g
K3PO4
212.3 g

7. השלבים בחישוב מסה מולרית
עמודים הם הרחבה ופירוט של 2 הדוגמאות שבעמודים קודמים

8. Molar Mass of CaCl2 מסה מולרית של תרכובת
We calculate the molar mass of CaCl2 to the nearest 0.1 g as follows.
Analyze the Problem.
Step 1 Obtain the molar mass of each element.
Given
Need
formula unit CaCl2
molar mass of Ca, Cl; CaCl2

9. המשך
We calculate the molar mass of CaCl2 to the nearest 0.1 g as follows.
Step 2 Multiply each molar mass by the number of
moles (subscript) in the formula.
Grams from 1 mole of Ca
Grams from 2 moles of Cl

10. המשך
We calculate the molar mass of CaCl2 to the nearest 0.1 g as follows.
Step 3 Calculate the molar mass by adding the
masses of the elements.

11. Learning Check מסה מולרית של תרכובת
Determine the molar mass of K3PO4 to 0.1 g.

12. Solution המשך Determine the molar mass of K3PO4 to 0.1 g.
Analyze the Problem.
Step 1 Obtain the molar mass of each element.
Given
Need
formula unit K3PO4
molar mass of K, P, O;
molar mass of K3PO4

13. Solution המשך Determine the molar mass of K3PO4 to 0.1 g.
Step 2 Multiply each molar mass by the number
of moles (subscript) in the formula.
Grams from 3 moles of K

14. Solution המשך Determine the molar mass of K3PO4 to 0.1 g.
Step 3 Calculate the molar mass by adding the
masses of the elements.

15. דוגמאות למסה מולרית של יסודות ותרכובות וכמותם בכוס
פוטסיוםדיכרומט
סוכרוז
32.1 g g g g g

16. תרגיל Learning Check What is the molar mass of each of the following?
A. K2O
B. Al(OH)3

17. פתרון Solution A. K2O 94.2 g/mole
2 mole K (39.1 g/mole) + 1 mole O (16.0 g/mole)
78.2 g g = g
B. Al(OH) g/mole
1 mole Al (27.0 g/mole) + 3 mol O (16.0 g/mole)
+ 3 mol H (1.01 g/mole)
27.0 g g g = g

18. תרגיל
Learning Check
Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?
1) g/mole
2) 262 g/mole
3) 309 g/mole

19. פתרון מקוצר
Solution
Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?
3) 309 g/mole
17 C (12.0) + 18 H (1.01) + 3 F (19.0)
+ 1 N (14.0) + 1 O (16.0) =
= 309 g/mole

20. פתרון מפורט
Solution
Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?
Analyze the Problem
Given
Need
molecular formula for Prozac, C17H18F3NO
molar mass of C, H, F, N, O
molar mass of C17H18F3NO

21. המשך
Solution
Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?
Step 1 Obtain the molar mass of each element. C g/mole N 14.0 g/mole
F g/mole O 16.0 g/mole
H g/mole

22. המשך
Solution
Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?
Step 2 Multiply each molar mass by the number of
moles (subscript) in the formula.

23. המשך
Solution
Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?
Step 3 Calculate the molar mass by adding the
masses of the elements.

24. Conversion Factors from Molar Mass
ביטויים לחישוב מסה מולרית
הרחבה
Conversion Factors from Molar Mass
Methane (CH4), known as natural gas, is used in gas stoves and gas heaters.
1 mole of CH4 = g of CH4
The molar mass of methane can be written as conversion factors

25. השלבים בחישוב מסה מולרית

26. Converting Mass to Moles, KCl
דוגמא- חישוב מסה מולרית
Converting Mass to Moles, KCl
How many moles are present in a 65.1 g sample of KCl?
Step 1 State the given and needed quantities.
Analyze the Problem.
Step 2 Write a plan to convert grams to moles.
grams of KCl Molar Mass moles of KCl
Given
Need
65.1 g of KCl
moles of KCl

27. המשך הדוגמא How many moles are present in a 65.1 g sample of KCl?
Step 3 Determine the molar mass and write
conversion factors.
Step 4 Set up the problem to convert grams to
moles.
1 mole of KCl = 74.6 g of KCl

28. תרגיל 1
Learning Check
Acetic acid C2H4O2 gives the sour taste to vinegar. Write two molar mass conversion factors for acetic acid.

29. פתרון Solution Acetic acid C2H4O2 gives the sour taste to vinegar.
Write two molar mass factors for acetic acid.
Calculate molar mass:
= 60.0 g/mole
1 mole of acetic acid = g acetic acid
Molar mass factors
1 mole acetic acid and g acetic acid
60.0 g acetic acid mole acetic acid

30. תרגיל 2
Learning Check
Acetic acid, C2H4O2, gives the sour taste to vinegar.
Calculate the moles of acetic acid present in a 25.8 g sample.

31. Solution פתרון Acetic acid, C2H4O2, gives the sour taste to vinegar.
Calculate the moles of acetic acid present in a 25.8 g sample.
Step 1 State the given and needed quantities.
Analyze the Problem.
Step 2 Write a plan to convert grams to moles.
grams of C2H4O Molar Mass moles C2H4O2
Given
Need
25.8 g acetic acid, C2H4O2
moles of C2H4O2

32. Solution המשך Acetic acid, C2H4O2, gives the sour taste to vinegar.
Calculate the moles of acetic acid present in a 25.8 g sample.
Step 3 Determine the molar mass and write
conversion factors.
1 mole of C2H4O2 = g of C2H4O2

33. Solution המשך Acetic acid, C2H4O2, gives the sour taste to vinegar.
Calculate the moles of acetic acid present in a 25.8 g sample.
Step 4 Set up the problem to convert grams to
moles.

34. Connections between Mass, Moles, and Particles
סיכום הקשר בין מסה, מולים וחלקיקים
Connections between Mass, Moles, and Particles

35. תרגיל
Learning Check
Calcium carbonate, CaCO3 is found in antacid tablets. If we have a mole sample of CaCO3, how many grams are present?

36. Solution
Calcium carbonate, CaCO3 is found in antacid tablets. If we have a mole sample of CaCO3, how many grams are present?
Step 1 State the given and needed quantities.
Analyze the Problem
Step 2 Write a plan to convert grams to moles.
moles of CaCO3 molar mass grams of CaCO3
Given
Need
0.320 mole CaCO3
grams of CaCO3

37. Solution
Calcium carbonate, CaCO3 is found in antacid tablets. If we have a mole sample of CaCO3, how many grams are present?
Step 3 Determine the molar mass and write
conversion factors.
1 mole of CaCO3 = g of CaCO3

38. Solution
Calcium carbonate, CaCO3 is found in antacid tablets. If we have a mole sample of CaCO3, how many grams are present?
Step 4 Set up the problem to convert moles to
grams.