CHEM LAB Report

 

 Experiment video. 

The formula of a solid 

DATA:

Mass of crucible after cleaning, g

10.7466

Mass of crucible + copper, g

11.1453

Mass of crucible + product, after 1rst
heating, g

11.2444

Mass of crucible + product after second
heating, if necessary, g

N/A

WATCH VIDEO FOR DESCRIPTIONS and RESULT of BRITTLENESS TEST
Description of reactants:

Description of reaction:

Description of product:

Result of the brittleness test:

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1. Each atom present is represented by its element
symbol.

2. The number of each type of atom is indicated by a
subscript written to the right of the element symbol.

3. When only one atom of a given type is present, the
subscript 1 is not written.

Rules for Writing Formulas

Total Number of Each Type of Atom
in a Chemical Formula

• Determine the number of each type of atom in
Mg(NO3)2.

• Mg(NO3)2 indicates a compound containing one
magnesium atom (present as the Mg2+ ion) and
two NO3− groups.

Mg: 1 = 1 Mg

N: 1 × 2 = 2 N
O: 3 × 2 = 6 O

Types of Chemical Formulas
• An empirical formula gives the relative number of atoms of

each element in a compound.

• A molecular formula gives the actual number of atoms of
each element in a molecule of the compound.

• For example, the molecular formula for hydrogen peroxide
is H2O2, and its empirical formula is HO.

• The molecular formula is always a whole number multiple
of the empirical formula.

Molar Mass Of Elements

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Converting between Grams and Moles
Calculate the number of moles of sulfur in 5

7

.8 g of sulfur.

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• Mass in grams of one mole of the substance:
Molar Mass of N = 14.01 g/mol

Molar Mass of H2O = 18.02 g/mol
(2 × 1.008 g) + 16.00 g

Molar Mass of Ba(NO3)2 = 261.35 g/mol
137.33 g + (2 × 14.01 g) + (6 × 16.00 g)

Counting Molecules by the Gram
Molar Mass

Molar Mass of K3PO4

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Mass Percent Composition of
Compounds

• The mass percent composition,
or mass percent, of an element
is the element’s percentage of the total mass of
the compound.

Finding Mass Percent Composition

• A 0.358-g sample of chromium reacts with
oxygen to form 0.523 g of the metal oxide.

• The mass percent of chromium is:

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Sarai Corte

September 14, 2020

E periment 01: Densit and Composition of Solutions

Professor Mohammad Salameh

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PURPOSE

This e periment aims to prepare sucrose solutions to determine the percentage of sucrose

and their densit using the Direct and Archimedean method then graphing our results to find the

percentage of sucrose in the unknown solution.

THEORY

For this e periment we needed to find the densit of the sucrose solutions, to start we

began b attempting to find the percentage of sucrose b mass. Based on the information given

to us in our data, to calculate this we can start b subtracting the mass of the beaker (g) with the

sucrose b the mass of the empt beaker (g). To calculate the percentage we also needed the

mass of sucrose and the mass of water:

Percentage b Weight of Sucrose =
a f c e

a f c e + a f a e 001

To calculate the densit we will use two different methods, the first is the Direct Method

which will help us collect data involving the mass of the 10 mL graduated c linder, masses of

the graduated c linder with the 10 mL of solutions, and the volumes of solutions. Using this

method we need to divide the mass of the 10 mL graduated c linder with the sucrose solution

minus the empt graduated c linder b the volume of sucrose which is 10 mL:

Densit = e f c e (10 L)
( a f he g ad. c i de / c e i ) (e g ad. c i de )

The second method used is the Archimedean Method, with this method we calculate the

densit b using the mass of the sinker (g), the mass of the sinker in the solutions (g), and the

mass of the sinker in the water (g). The equation we will use is:

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Densit =
1.0 g/ L

( a f i e i ai ) ( a f i e i H 2O)

( a f he i e i ai ) ( a f i e i i )

When we obtain all densities and percentages of sucrose b mass we can put our

information in a line graph and predict the percentage of sucrose in the unknown solution.

PROCEDURE

Goldwhite, H. et al. ​E e i e i Ge e a Che i ; ​California State Universit , Los

Angeles, 2018; p 1-5

DATA

Table 1: Mass of Solution

Solution Mass of empt
beaker, g

Mass of beaker +
sucrose, g

Mass of beaker +
sucrose + ,gOH 2

A 59.11 g 66.62 g 104.85 g

B 68.25 g 82.24 g 118.35 g

C 68.79 g 98.79 g 128.35 g

Table 2: Mass of Graduate C linder

Mass of empt 10 mL grad. C linder, g 25.41

Mass of Graduate C linder + 10 mL Solution A, g 35.6

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Mass of Graduate C linder + 10 mL Solution B, g 36.15

Mass of Graduate C linder + 10 mL Solution C, g 37.23

Mass of Graduate C linder + 10 mL Unknown, g 35.79

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Table 3: Mass of Sinker

Mass of Sinker, g

In Air 10.77 g

In Water 9.32 g

In Solution A 9.25 g

In Solution B 9.20 g

In Solution C 9.05 g

In Unknown 9.23 g

RESULTS AND DISCUSSION

Calculations for Solution B:

% Composition of Sucrose b Mass = = = 0.2792 100 = 27.92%82.24 68.2513.99 + (118.35 82.24) 50.10
13.99

(Direct Method) Densit = ​ = = 1.074 g/mL10 L
36.15 25.41 10.74

10 L

(Archimedean Method) Densit = = = 1.083 g/mL
1.0 g/ L

10.77 9.32
10.77 9.20

1.45
1.57

We use the Direct Method and the Archimedean Method on each solution to find and

calculate the densit of each solution, including the unknown. As shown in Table 4 we used the

Direct Method and in Table 5 we used the Archimedean Method:

Table 4: Densit of Sucrose using the Direct Method

Solution Mass of grad. c l. + 10.0 mL
solution

Densit , g/mL

A 35.65 g 1.024 g/mL

B 36.15 g 1.074 g/mL

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C 37.23 g 1.182 g/mL

Unknown 35.79 g 1.038 g/mL

Table 5: Densit of Sucrose using the Archimedean Method

Solution Densit , g/mL

A 1.048 g/mL

B 1.083 g/mL

C 1.186 g/mL

Unknown 1.062 g/mL

In addition to the densities, to make our line graph and infer the composition of the

unknown solution we also needed the percentage of composition of sucrose in the solutions using

the formula listed in the theor . In Table 6 we can see the results:

Table 6: % Weight of Sucrose

Solution % Composition of Sucrose b Mass

A 16.41%

B 27.92%

C 50.36%

After collecting and putting our calculations into charts we are prepared to put it into a

line graph and attempt to find the percent of sucrose in the unknown solution. In the -a is, we

put our percentage of sucrose from our known solutions, and on the -a is, we noted the

densities. We know that the unknown solution has a densit of 1.038 g/mL so if we attempted to

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align our results on the line of the graph we can see that the percentage of sucrose in the

unknown solution is about 20%.

Graph 1: Densit and Concentration of Sucrose Solutions

During this e periment, there could have been s stematic and random errors. One source

of error ma have been consistentl taking measurements incorrectl , when measuring one of the

solutions if someone did not know to take proper measurements the could have continued to

collect inaccurate data. A wa to avoid these errors is to comprehend what the e periment is

asking and to know how to use our equipment properl . Another source of error is random

error, this t pe of error is more difficult to detect because it is not predictable. This could have

occurred during the e periment b not measuring the solutions the same wa each time. Most

times ou cannot eliminate random errors from our e periment but looking over our data twice

and double-checking our calculations could be one wa to evade this error.

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CONCLUSION

The purpose of this e periment was to prepare the sucrose solutions and find their densit

and percent of sucrose using the direct and Archimedean method. After finding this data we

gathered it to find the densit and percent of sucrose in the unknown solution. These results are

reasonable when ou look at our data because the densit of our unknown solution lies between

solutions A and B, solution A had a 16.41% of sucrose, and solution B had a 27.92% of sucrose.

In the final results, we can see in Graph 1 that the unknown solution had an estimated value of

20% of sucrose, which does lie between 16.41% and 27.92%.

Something new that I was able to learn during this e periment was to understand how to

use new equations b utili ing different methods. The different equations we needed to use to

find densit and percent of sucrose were easier than I thought and for future e periments, a wa

to improve the accurac of our results its ver important for us to understand the equations we

are given. To use these equations or an data, being knowledgable on what the are asking of

ou and knowing how to gather necessar information is crucial to a successful e periment.

REFERENCE

Goldwhite, H. et al. ​E e i e i Ge e a Che i ; ​California State Universit , Los
Angeles, 2018; p 1-5