Preliminary experiments HELP, please!!! (1 Viewer)

[anigaloyan]

Hi everyone!!!

I am working on my syllabuses , and there are many experiments on 'Water' topic, that we havent demonstrated AT ALL!!! I am really worried, as there is no time left
So could u please give me some links, websites, ideas , or write ur methods and results of mandatory pracs in this topic. At least I will have idea about the experiments.

IT IS VERY IMPORTANT , and help will be so much appreciated.
Thanks a lot!!
​

 

[Gussy Booo]

Write down what the syllabus says and I'll tell you.

 

[anigaloyan]

· perform an investigation involving calculations of the density of water as a liquid and a solid using: density=mass/volume
· perform a first-hand investigation, using micro-techniques, to compare the solubility of appropriate salts in solution through precipitation reactions
· perform a first-hand investigation to make solutions to specified volume-to-volume and mass-to-volume specifications and dilute them to specified concentrations
(cV = constant)

choose resources and perform a first-hand investigation to measure the change in temperature when substances dissolve in water and calculate the molar heat of solution<O></O>


process and present information from secondary sources to assess the limitations of calorimetry experiments and design modifications to equipment used</O>

These are all the experiments that I need, if u can help with any of them I will be very thankfull!!!

 

[Gussy Booo]

For :

choose resources and perform a first-hand investigation to measure the change in temperature when substances dissolve in water and calculate the molar heat of solution>>


AIM


To determine the heat energy adsorbed or lost from the two compounds Ammonium Chloride and Sodium Hydroxide

(Hmmm, the compounds that you're using might not be the same....)
(For this practical we used: ∆H=-mC∆T)

EQUIPMENT

1 x 100ml Cylinder (To measure the water the amount of water)

2 x 35mL Beakers (To place the compounds in)

5.35g of Ammonium Chloride (We actually calculated the mass
)
4g of Sodium Hydroxide (Same as Ammonium Cl)

2 Paper Cups (This is where the process took place. Water + Compound)

Microscaler (Very accurate scaling measure. We measured the mass of the compounds through this)

Thermometer (Measure the change in temperature)

100ml of water (The amount of water to be put with the compound)

CALCULATING THE MASS

So we basically calculated the mass of the compounds. This is what our teacher told us.

"We want 0.1n"

In other words, we want 0.1 moles of the substance.

In order to calculate the mass we use the formula :

n = m/mm

Number of Moles = Mass / Molecular Mass.

Ammonium Chloride

0.1 = x / 53.49 (Found through periodic table)

.'. Mass = 5.35g

Sodium Hydroxide

0.1 = x / 40

.'. Mass =4g.


PROCEDURE

1. Obtain 5.35g of Ammonium Chloride and 4g of Sodium Hydroxide
2. Measure 100mL of water
3. Pour water into paper cup
4. Read the initial temperature of water
5. Place the ammonium chloride into water and stir until all dissolved using the thermometer as a stiring rod
6. Read final temperature
7. Repeat steps 4,5,6 using Sodium hydroxide
8. Calculate.

The main objective of the above is to find the change in temperature

OR ∆T.

∆T = ( Tf - Ti )
∆T = ( Final temperature - Initial Temperature)

Ammonium Chloride

∆T = 9 - 13
∆T = -4

Sodium Hydroxide
∆T = 21.25-9
∆T = 12.25

-----------------------------------

∆H=-mC∆T

We've got to find the pro numerals of the equation

For ammonium chloride

m = 0.1L
C = 4.18 (Specific heat capacity of water)
∆T = -4

.'. ∆H=-(0.1)(4.18)(-4 )

∆H= 1.672

Its positive .'. endothermic

i cbff now lol

same shit with sodium hydroxide.........

then you gotta find the molar heat of solution..

So taking Ammonium Chloride in example

∆H= 1.672

This is where i got lazy in the prac. This might actually take 80mins....it's soo long UGHH !! LFMAO! IM DEAD I NEED TO DO MY MATHS HOMEWORK !!

okokokok.

So remember we want 0.1n ?
This is the part where im not so comfortable in...

But heat of solution = j/mol^-1
sooooooo we got 0.1 moles...and the energy is -89.452

therefore

1.672
----------
0.1

.'. molar heat = 16.72

 

[Gussy Booo]

For :

process and present information from secondary sources to assess the limitations of calorimetry experiments and design modifications to equipment used


1) Instead of using a mercury thermometer, a digital thermometer with significant figures would prove to be more accurate

2) Using an insulator over the cups to prevent heat loss of conduction and convention.

 

[Gussy Booo]

For perform a first-hand investigation, using micro-techniques, to compare the solubility of appropriate salts in solution through precipitation reactions

Substance Reaction With water
Sucrose- Soluble
Iodine- Slight Solubility
Ammonium Chloride - Soluble (Endothermic)
Sodium Acetate- Soluble
Acid Stearic- Slight Solubility
Potassium Bromide- No Solubility
Sand- No Solubility
Barium Sulphate- Insoluble
Ethanol Absolute- Very soluble
H-Hexane-Immiscible

Conclusion: Substances with hydrogen bonds will be soluble in water. The more hydrogen bonds, the greater its solubility. If there are no hydrogen bonds present, other bonds such as dispersion bonds or/and dipole-dipole forces may be present, though, they are easily beakable

 

[anigaloyan]

Thanks a lot! This was heaps helpful!!!