Category: Science

GLOSSARY:

Standard Solution: A standard solution is a solution whose concentration is known accurately

Standard Enthalpy change of reaction: Standard enthalpy change of reaction, is the enthalpy change when a reaction occurs in the molar quantities shown from the chemical equation, under standard conditions with all reactants and products in their standard states.

Standard Enthalpy change of formation: Standard enthalpy change of formation, is the enthalpy change when 1 mole of a compound is formed from its elements in their standard states, under standard conditions.

Standard Enthalpy change of combustion: Standard enthalpy change of combustion, is the enthalpy change when 1 mole of a substance is burned completely in oxygen under standard conditions with all reactants and products in their standard states.

Standard Enthalpy change of neutralization: Standard enthalpy change of neutralization, is the enthalpy change when solutions of an acid and an alkali react together to form 1 mole of water, under standard conditions.

Exothermic Reactions: Exothermic reactions give out energy to their surroundings. the products of the reaction end up with less energy than the reactants. This means that the enthalpy change for the reaction will be negative.

Endothermic Reactions: Endothermic reactions take in energy from their surroundings. this means that the products of the reaction have more energy than the reactants, so the enthalpy change for the reaction is positive.

Task 1:

Make a standard solution:

• Place the watch glass on the balance, making sure that it is set at zero. Then carefully weigh the amount of substance needed
• Next transfer the measured amount of the substance in a beaker. From here add water to dissolve it.
•  With the glass rod stir the the solution until all the solid is dissolved, next pour the solution into the volumetric flask.
• Now, water must be added just below the line on the volumetric flask. Making sure the meniscus is on the line, this can be done by adding a few drops with a teat pipette.
• Following this, you should place the lid of the volumetric flask on and shake the flask a couple times to mix the the solution.
• The number moles needed required for the solution.
• Work out the required volume and concentration needed ( m= C times V ). Measurements for Concentration is dm^3 and Volume would be dm3.
• To be able to find the required measurement. you will need to divide the volume by 1000 to get it in dm3.
• From here you should find the RFM ( relative formula mass) of the chosen substance.

Once all the measurements are done and accurate, move on to task two.

Task 2:

• Place the balance on a nice and even surface ( making sure its calibrated & set at zero)
• Place the watch glass on the balance and measure the mass of solution needed.
• Pour the hydrochloric acid into the burette, leaving the tap open with a beaker under the tap ( You can use a small funnel to make it easier )
• Stop when the burette is full. Once it is full close the tap, from here add more of the solution up to the zero mark
• Using the pipette to transfer the sodium hydroxide solution to the volumetric flask. Once this is completed two drops of the phenolphthalein indicator should be added
• With the glass rod mix the solution gently.
• Place the volumetric  flask on piece of clean white paper under the burette tap.
• From here hydrochloric acid should be added to the sodium hydroxide solution very slowly, mix gently after each time the hydrochloric acid is added.
• Continue until solution goes a clear colour
• The coloured solution should then be rinsed down the sink.
• The HCL should be added drop by drop into the NaOH until the solution goes from pink to colorless, from this point no more HCL should be added and the solution should be recorded.

Task 3:

• Convert the 100 ml to dm^3 – 0.1dm^3  ( 100/1000 )
• 0.5/0.1 = 0.2 using the formula m = C times V
• Hydrochloric acid + sodium hydroxide → sodium chloride + water
• HCL + NaOH —-> NaCl + H2O

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