Student Worksheet for Chemistry Fundamentals · Advanced Chemistry Chemistry Fundamentals

Advanced Chemistry Chemistry Fundamentals

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Student Worksheet for Chemistry Fundamentals

Attempt to work the following practice problems after working through the sample problems in

the videos. Answers are given on the last page(s).

Relevant Equations/Information

Molecular Weight: Σ (𝐴𝑡𝑜𝑚𝑖𝑐 𝑊𝑒𝑖𝑔ℎ𝑡 ∗ 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡ℎ𝑎𝑡 𝐴𝑡𝑜𝑚)

Number of Moles: 𝐺𝑟𝑎𝑚𝑠 𝐺𝑖𝑣𝑒𝑛

𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑊𝑒𝑖𝑔ℎ𝑡

Excess Reagent Left: 𝑆𝑡𝑎𝑟𝑡𝑖𝑛𝑔 𝐴𝑚𝑜𝑢𝑛𝑡 − 𝐴𝑚𝑜𝑢𝑛𝑡 𝑈𝑠𝑒𝑑 𝑏𝑦 𝑡ℎ𝑒 𝐿𝑖𝑚𝑖𝑡𝑖𝑛𝑔 𝑅𝑒𝑎𝑔𝑒𝑛𝑡

Limiting Reagent: Reagent that Yields the Least Amount of Product

Rules for Significant Figures

1. All nonzero digits are significant.

2. Zeroes at the beginning of a number are not significant.

3. Zeros between significant digits are significant.

4. All final zeroes to the right of a decimal are significant.



1. How many significant figures are in each of the following?

a) 1.040 _____

b) 0.2 _____

c) 5.41 _____

d) 240 _____

2. You obtained the following data during an experiment. If the known rate of product

appearance (how quickly the chemical reaction happens) is 1.5 moles per second, is your data

precise, accurate, or both? Briefly explain your choice. A third column has been included for you

to calculate moles per second against the known value.

Time (Seconds) Moles Produced (Total) Moles Per Second

1 1.3

2 2.7

3 4.0

4 5.5

5 6.9

3. Using Dimensional Analysis, convert 2 weeks (14 days) to minutes.

4. How many furlongs are required to install a 275-foot fence? 7.92 inches = 1 link; 100 links = 1

chain; 10 chains = 1 furlong; 80 chains = 1 mile.



Balance the equations for Numbers 5-7.

5. ____ CaCO3 + ____ HF ____ H2CO3 + ____ CaF2

6. ____ Na3PO4 + ____ H2O ____ NaH2PO4 + ____ NaOH

7. ____ CO2 + ____ N2 ____ CO + ____ NO

8. Calculate the molecular weight of C6H5OH (phenol).

9. How many molecules of phenol (#8) are in 250 g?



10. How many grams of CHCl3 are in 4.32* 1025 molecules?

11. Using the following equation:

2 NaOH + H2SO4 2 H2O + Na2SO4

How many grams of sodium sulfate will be formed if you start with 175 grams of sodium

hydroxide and you have an excess of sulfuric acid?


Fe2O3 + 3 H2 2 Fe + 3 H2O

Calculate how many grams of water can be made from 19 grams of Fe2O3.




NaIO3 + 6 HI 3 I2 + NaI + 3 H2O

Calculate the number of moles and the number of grams of Iodine (I2) that can be made this way

from 70.5 grams of HI.


2 H2O 2 H2 + O2

How many grams of water were needed to produce 21 moles of H2?

15. Using the equation:

H2SO4 + SrCl2 2HCl + SrSO4

How many grams of strontium chloride react with 375 grams of sulfuric acid?




4Al + 3O2 2Al2O3

How many grams of aluminium oxide will form if 7.5 moles of O2 and 7.5 moles of Al react?

Which is the limiting reagent?


6 CO2 + 6 H2O C6H12O6 + 6 O2

How much excess reagent is left over if 45 grams of CO2 react with 36 grams H2O?



1. How many significant figures are in each of the following?

a) 1.040 _4____

b) 0.2 __1___

c) 5.41 _3___

d) 240 __2__ This 0 is not significant because there is no decimal in the number.

2. You obtained the following data during an experiment. If the known rate of product

appearance (how quickly the chemical reaction happens) is 1.5 moles per second, is your data

precise, accurate, or both? Briefly explain your choice. A third column has been included for you

to calculate moles per second against the known value.

Time (Seconds) Moles Produced (Total) Moles Per Second

1 1.3 1.3

2 2.7 1.4

3 4.0 1.6

4 5.5 1.5

5 6.9 1.4

Your measured values can be considered accurate and precise. While they are not exactly 1.5 all

the time, they are extremely close to the value (making them accurate) and close together

(making them precise).

3. Using Dimensional Analysis, convert 2 weeks (14 days) to minutes.

14 days 24 hours 60 minutes 20,160 minutes

1 day 1 hour

4. How many furlongs are required to install a 275-foot fence? 7.92 inches = 1 link; 100 links = 1

chain; 10 chains = 1 furlong; 80 chains = 1 mile.

275 ft 12 in 1 link 1 chain 1 furlong 0.42 furlongs

1 ft 7.92 in 100 link 10 chains



Balance the equations for Numbers 5-7.

5. _1__ CaCO3 + _2__ HF __1_ H2CO3 + __1__ CaF2

6. __1_ Na3PO4 + _2__ H2O _1__ NaH2PO4 + __2_ NaOH

7. _2__ CO2 + _1__ N2 __2_ CO + __2_ NO

8. Calculate the molecular weight of C6H5OH (phenol).

Atom Quantity Atomic Weight Total

Carbon 6 12 72

Hydrogen 6 1 6

Oxygen 1 16 16

Molecular Weight 94 g/mol

9. How many molecules of phenol (#8) are in 250 g?

250 g Phenol 1 mole Phenol 6.022 *1023 molecules

Phenol

1.60 *1024 molecules Phenol

94 g Phenol 1 mole Phenol

10. How many grams of CHCl3 are in 4.32* 1025 molecules?

4.32*1025molecules CHCl3 1 mole CHCl3 119 g CHCl3 8.36 kg CHCl3

6.022*1023 molecules CHCl3 1 mole CHCl3




2 NaOH + H2SO4 2 H2O + Na2SO4

How many grams of sodium sulfate will be formed if you start with 175 grams of sodium

hydroxide and you have an excess of sulfuric acid?

175g NaOH 1 mole NaOH 1 mole Na2SO4 142 g Na2SO4 310.63 g Na2SO4

40 g NaOH 2 moles NaOH 1 mole Na2SO4


Fe2O3 + 3 H2 2 Fe + 3 H2O

Calculate how many grams of water can be made from 19 grams of Fe2O3.

19 g Fe2O3 1 mole Fe2O3 3 moles H2O 18 g H2O 6.41 g H2O

160 g Fe2O3 1 mole Fe2O3 1 mole H2O


NaIO3 + 6 HI 3 I2 + NaI + 3 H2O

Calculate the number of moles and the number of grams of Iodine (I2) that can be made this way

from 70.5 grams of HI.

70.5 g HI 1 mole HI 1 mole I2 0.28 moles I2

128 g HI 2 mole HI

Number of moles = 𝐺𝑟𝑎𝑚𝑠 𝑌𝑜𝑢 𝐻𝑎𝑣𝑒

𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑊𝑒𝑖𝑔ℎ𝑡 Solving for how many grams you have.

Grams You Have = Number of moles * Molecular Weight

= 0.28 moles * 254 g/mol

= 71.12 g I2

Note that the stoichiometric ratio between HI and I2 is 6:3 in the equation. The ratio was

simplified to 2:1 in calculations. If you used 6:3 instead, your answer will still be the same.




2 H2O 2 H2 + O2

How many grams of water were needed to produce 21 moles of H2?

21 moles H2 1 moles H2O 18 g H2O 378 g H2O

1 mole H2 1 mole H2O

Like in #13, the reactant:product ratio was again simplified.

15. Using the equation:

H2SO4 + SrCl2 2HCl + SrSO4

How many grams of strontium chloride react with 375 grams of sulfuric acid?

375 g H2SO4 1 mole H2SO4 1 mole SrCl2 158.5 g SrCl2 606.5 g SrCl2

98 g H2SO4 1 mole H2SO4 1 mole SrCl2


4Al + 3O2 2Al2O3

How many grams of aluminium oxide will form if 7.5 moles of O2 and 7.5 moles of Al react?

Which is the limiting reagent?

To determine the limiting reagent, you must find out how much product each of the reactants

produces. The one that produces less (aka runs out) is the limiting reagent.

7.5 moles O2 2 moles Al2O3 5 moles Al2O3

3 moles O2

7.5 moles Al 2 moles Al2O3 3.75 moles Al2O3

4 moles Al

The Al is your limiting reagent.

Now, determine how many grams of product will be produced by 7.5 moles of Al.




𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑊𝑒𝑖𝑔ℎ𝑡 Solving for how many grams you have.

Grams You Have = Number of moles * Molecular Weight

= 3.75 moles * 102 g/mol

= 382.5 g Al2O3


6 CO2 + 6 H2O C6H12O6 + 6 O2

How much excess reagent is left over if 45 grams of CO2 react with 36 grams H2O?

This problem proceeds similar to #16, but with a different step at the end because you are not

solving for how much product is being made. You must first determine the limiting reagent, and

then determine how much of the excess reagent is used by the limiting reagent. Also, you are

given grams of reactants in this question, so you must first convert the grams to moles.

CO2:



= 45 𝑔

44 𝑔/𝑚𝑜𝑙

= 1 mole CO2

H2O:



= 36 𝑔

18 𝑔/𝑚𝑜𝑙

= 2 moles H2O

Again, noting that you are not solving for the amount of a particular product, you may use either

to determine which reagent is limiting, but you must use the same product for both reagents.

1 mole CO2 1 mole C6H12O6 0.17 moles C6H12O6

6 mole CO2

2 moles H2O 1 mole C6H12O6 0.67 moles C6H12O6

6 mole H2O

The CO2 is the limiting reagent. Now, solve for how much H2O was consumed by the CO2.



1 mole CO2 1 mole H2O 1 mole H2O consumed

1 mole CO2

(Again, the molar ratios have been simplified.)

To solve for how much excess is left,

Excess reagent left = Number of moles you started with – Number of moles consumed

= 2 moles H2O – 1 mole H2O

= 1 mole H2O remaining

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Student Worksheet for Chemistry Fundamentals · Advanced Chemistry Chemistry Fundamentals

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