Chemistry Exam 4

Pretend that you are working in a lab group. **If your grade on a laboratory depended on how accurately and precisely your team measures the length of a sheet of paper, what would be some of your team's concerns about your group’s measurement?**

Group gets the right measurement, Everyone in group gets the same answers, everyone uses an accurate ruler, and everyone uses the same type of measuring units (Like inches, centimeters, etc.)

How would your team determine which measurement would be the one reported?

Take the average of the group’s measurement

Which of the following describes the first target?

Accurate

Which of the following describes the second target?

Precise

Which of the following describes the third target?

Both

Which of the following describes the fourth target?

Neither

Which of the following is a simple explanation for accuracy?

Accuracy means getting the right answer

Which of the following is a simple explanation for precision?

Precision means getting the same answer every time

Determine if the following readings from a breath analysis for blood alcohol are accurate, precise, both, or neither for a person arrested with a true blood alcohol concentration of 0.0764%. Recall in most states the legal limit is 0.08%

Box 1- 0.08

Box 2- 0.1

Box 3- 0.076

Box 4- 0.0504

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The reading of 0.08 is..

Accurate

Determine if the following readings from a breath analysis for blood alcohol are accurate, precise, both, or neither for a person arrested with a true blood alcohol concentration of 0.0764%. Recall in most states the legal limit is 0.08%

Box 1- 0.08

Box 2- 0.1

Box 3- 0.076

Box 4- 0.0504

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Why did you chose this answer for the 0.08% reading?

It is close to the true blood alcohol concentration of 0.0764% and it is not precise since it only measures to 0.08 Instead of 0.0764

Determine if the following readings from a breath analysis for blood alcohol are accurate, precise, both, or neither for a person arrested with a true blood alcohol concentration of 0.0764%. Recall in most states the legal limit is 0.08%

Box 1- 0.08

Box 2- 0.1

Box 3- 0.076

Box 4- 0.0504

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The reading of 0.1 is?

Neither

Determine if the following readings from a breath analysis for blood alcohol are accurate, precise, both, or neither for a person arrested with a true blood alcohol concentration of 0.0764%. Recall in most states the legal limit is 0.08%

Box 1- 0.08

Box 2- 0.1

Box 3- 0.076

Box 4- 0.0504

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Why did you choose this answer for 0.1% reading?

This answer is not accurate because it indicates that the person was well over the legal limit of 0.08% when the person was actually slightly below it and it is not precise since it only measures to one decimal place instead of 4 decimal places like the true reading.

Determine if the following readings from a breath analysis for blood alcohol are accurate, precise, both, or neither for a person arrested with a true blood alcohol concentration of 0.0764%. Recall in most states the legal limit is 0.08%

Box 1- 0.08

Box 2- 0.1

Box 3- 0.076

Box 4- 0.0504

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The reading of 0.076% is?

Both (accurate and precise)

Determine if the following readings from a breath analysis for blood alcohol are accurate, precise, both, or neither for a person arrested with a true blood alcohol concentration of 0.0764%. Recall in most states the legal limit is 0.08%

Box 1- 0.08

Box 2- 0.1

Box 3- 0.076

Box 4- 0.0504

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Why did you choose this answer for 0.076%.

The answer is accurate compared to the true value and precise since it measures to 3 decimal places.

Determine if the following readings from a breath analysis for blood alcohol are accurate, precise, both, or neither for a person arrested with a true blood alcohol concentration of 0.0764%. Recall in most states the legal limit is 0.08%

Box 1- 0.08

Box 2- 0.1

Box 3- 0.076

Box 4- 0.0504

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The reading of 0.0504 is?

Precise

Determine if the following readings from a breath analysis for blood alcohol are accurate, precise, both, or neither for a person arrested with a true blood alcohol concentration of 0.0764%. Recall in most states the legal limit is 0.08%

Box 1- 0.08

Box 2- 0.1

Box 3- 0.076

Box 4- 0.0504

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Why did you choose this answer for 0.0504?

This answer is precise since it measures to 4 decimal places but it is not accurate since it is not close to the true value

What is the difference in 100, 100. and 100.0

The difference is the number of sig figures and that each measurement were made to different degrees of precision

How many sig figures in 0.002304

4

How many sig figs in 0.3450

4

How many sig figures in 1.0230560

8

What is the exact number example?

There are 14 students in this class

What is the number before the multiplication sign called? (1.00 x 10^23)

Mantissa

What is the number after the multiplication sign called? (1.00 x 10^23)

exponent

How many sig figs in 298.0?

4

Convert 298.0 to scientific notation

2\.980 x 10^2

How many sig figs in 0.045

2

Convert 0.045 to scientific notation?

4\.5 x 10^-2

How many sig figs in 3100

2

Convert 3100 to scientific notation

3\.1 x 10^3

How many sig figs in 0.0000001

1

How many sig figs in 1,035,000

4

Convert 1,035,000 to scientific notation

1\.035 x 10^6

What unit would you use to find the mass of a chemical?

Kilograms

What unit would you use to find the volume of a solution?

liters

How many grams are in 1 kilogram?

1000 grams

How many grams are in 2.56 kg?

2560 g

How any kilograms are in 3456 grams

3\.456 kg

How many miligrams are in 1 gram

1000 mg

How many miligrams are in 0.456 g

456 mg

How many grams are in 898 mg?

0\.898

If the mass of an average grape is 1.6 g and someone buys 484 g of grapes (less stems), how many grapes did they buy?

484 g ÷ 1.6 g/grape = 302.5 grapes

**Assuming all the grapes are in fact whole, how can you account for the calculated “half” of a grape?**

All of the grapes do not weigh exactly 1.6 g. This results in the calculation of half of a grape.

\n **How would you set up the problem to determine how many of the screws used above were contained in a 50 pound box?**

(50 pounds) x (screws/pound) = screws

When building a deck, many people use screws to hold down the decking. If you decided to use 12 screws per plank and had 100 planks, that would be 1200 screws. Screws are sold by the pound in most hardware stores. If you used screws that are 150 screws per pound, how many pounds of screws do you need to complete the job?

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**If you were unsure how to do this problem, what should you look at to help you find the solution?**

You should arrange the problem to where the units cancel out, and you are left with the units that you want.

When building a deck, many people use screws to hold down the decking. If you decided to use 12 screws per plank and had 100 planks, that would be 1200 screws. Screws are sold by the pound in most hardware stores. If you used screws that are 150 screws per pound, how many pounds of screws do you need to complete the job?

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**How many of the screws above are contained in a 50 pound box?**

7500 screws

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(50 pounds) x ( 150 screws/ pound) = 7500 screws.

What is the mass of two C atoms?

24\.02 amu

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The mass of two C (carbon) atoms is 24.02. 12.01 amu + 12.01 amu = 24.02 amu. When referring to the mass of the elements on the periodic table, we use the units of amu and not grams.

What is the mass of six H atoms?

6\.06 amu

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6 H atoms have a mass of 6.06 amu. 6 \* 1.01 amu = 6.06 amu

What is the mass of one O atom?

16\.00 amu

What is the combined mass of two C atoms, six H atoms, and one O atom?

46\.08 amu

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The combined mass of 2 C atoms, 6 H atoms, and 1 O atom is 46.08 because 2(12.01 amu) + 6(1.01 amu) + 16.00 amu = 46.08 amu

What is the mass of a molecule with the formula C3H9N?

59\.13 amu

What is mass of one dozen molecules of C3H9N?

709\.56 amu

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12 \* 59.13

How many eggs are in 2 dozen?

24

How many stars (6) are in a dozen?

0\.5

How many molecules are in 2 moles of molecules?

1\.204 x 10^24 molecules

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There are 1.204 x 10^24 molecules in 2 moles of molecules because 2 \* 6.022 x 10^23 = 1.204 x 10^24.

How many moles of atoms are 2.007 x 10^23 atoms?

0\.3332 mol

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There are 0.3332 moles in 2.0007 x 10^23 atoms because

 (2.007 x 10^23 atoms) ÷ (6.022 x 10^23 moles/atom) = 0.3332 moles.

What is the average mass for a single atom of Na?

22\.99 amu

What is the average mass for 6.022 x 10^23 atoms of Na?

22\.99 g

What is the average mass of one mole of Na?

22\.99 g

What is the average mass for 0.50000 mole Na atoms?

11\.49 g

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0\.5 x 22.9

is it necessary to use the value of Avogadro's number (6.022 x 10^23) to determine the mass of 1.0000 mole or 0.50000 mole of Na atoms? Why or why not?

No, you do not need Avogadro's number because the periodic table tells the mass in grams of one mole of Na. (Moles) x (g/mol) = grams

What is the mass of 2 mol C?

24\.02 g

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The mass of 2 mol of C is 24.02 g because 2 mol C x (12.01 g/mol) = 24.02 g.

2 x 12.01 g= 24.02 g

What is the mass of 6 mol H?

6\.06 g

what is the mass of 1 mol of O?

16\.00

What is the combined mass of 2 mol C, 6 mol H, and 1 mol O?

46\.08 g

What is the mass of one mole of molecules with the formula C3H9N?

59\.13 g

What is the mass of 3.3 moles of molecules of C3H9N?

195\.1 g

**How many eggs are contained in the following?**

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0\.25 dozen eggs

3 eggs

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0\.25 x 12

**How many eggs are contained in the following?**

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0\.85 moles of eggs

5\.119 x 10^23

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0\.85 moles of eggs x (6.022 x 10^23 eggs/mol) = 5.119 x 10^23 eggs

**How many carbon atoms are contained in the following?**

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3\.48 moles of carbon atoms

2\.10 x 10^24

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3\.48 moles of C x (6.022 x 10^23 atoms/mol) = 2.10 x 10^24

**How many carbon atoms are contained in the following?**

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0\.035 moles of carbon atoms

2\.1 x 10^22

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There are 2.1 x 10^22 carbon atoms in 0.035 moles of carbon atoms. 

Would you expect 8.8 x 10^23 carbon atoms to be greater than, less than or equal to 1 mole?

Greater then.

How many moles of carbon atoms are found in 8.8 x 10^23 carbon atoms?

1\.5 moles.

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8\.8 x 10^23 C atoms x ( 1 mol/6.022 x 10^23 atoms) = 1.5

Would you expect 6.24 x 10^22 carbon atoms to be greater than, less than or equal to 1 mole?

Less

How many moles of carbon atoms are found in 6.24 x 10^22 carbon atoms?

0\.104 moles

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6\.24 x 10^22 x (1 mol/6.022 x 10^23 atoms)=0.104

**If an average egg weighs 50 g, how much does each of the following weigh?**

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1 dozen eggs

600 g

**If an average egg weighs 50 g, how much does each of the following weigh?**

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1 mole eggs

3\.01 x 10^25 g

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50 g x (6.022 x 10^23 moles/g) = 3.01 x10^25 g

**If an average atom of carbon weighs 1.9945 x 10^-23 g, how much does each of the following weigh?**

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1 dozen carbon atom

2\.3934 x 10^-22 g

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12 C atoms x (1.9945 x 10^-23 g/atom) = 2.3934 x 10^-22 g

What is the mass of 1.35 mole O2 molecules?

43\.2 g

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1\.35 mole x (32.0 g/ mol) = 43.2 g

\*\*O2 = 2 x 16 = 32

Is the reaction N2(g) + H2(g) → NH3(g) balanced?

No

For the balanced reaction CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g), **how many molecules of CH4 are required to make 2 molecules of H2O?**

1 molecule

Based on that ratio determined in Q4, **how many moles of O2 are required to completely consume 9 moles of CH4? (1:2 ratio)**

18 moles of O2

If 4 moles of CH4 were used in the reaction CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g), **what is the maximum number of moles of CO2 you could expect the reaction to produce?**

4 moles. (1:1 ratio)

What is the maximum number of moles of H2O you could expect the reaction to produce if 4 moles of CH4 were used?

8 moles of H2O

If only 0.5 moles of O2 were used in the reaction CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g), **what is the maximum number of moles of CO2 you could expect the reaction to produce?**

0\.25 moles.

How many moles are contained in 24 g CH4?

1\.5 moles

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24 g x (1 mol/ 16.04 g) = 1.5 moles

How many moles of CO2 could be produced if 24g of CH4 were used in the reaction CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)?

1\.5 moles of CO2

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Found the moles of CH4 and its same number since 1:1 ratio.

What type of mixture is antifreeze in water?

Homo mixture

What type of mixture is brass (copper and zinc)

homo mixture

what mixture is dry air

homo mixture

what mixture is black coffee

homo mixture

what mixture is real bannana pudding

hetero mixture

what type of mixture is ice tea

hetero mixture

What are all the possible solutes in Dr. Pepper

Carbon dioxide, sugar, flavoring

Is 1 teapsoon of salt in water statured or unsaturated?

Unsaturated

Is 1 pound of salt in water statured or unsaturated?

Statured

Is 1 teaspoon of sand in water statured or unsaturated?

Statured

Is 1 teaspoon of baking soda in water statured or unsaturated?

Unsaturated

Is 1 teaspoon of acetone in water statured or unsaturated?

Unsaturated

What is the solvent in Dr. Pepper

Water

Which would be more soluble at 10C, a gas or a solid?

Gas

Which would be more soluble at 90C, a gas or a solid?

Solid