Chemistry C3 3.2 Energy transfers in solutions.

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How can we calculate the energy change for reactions in solution?
By measuring the temperature change and using the equation: Q = mc(triangle shaped symbol)T.
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When is energy transferred to or from a solution?
When a reaction takes place in the solution.
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Where is it best to do energy transfers in solutions to reduce energy transfers to the surroundings?
In an insulated container.
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How can the temperature change of the solution be used?
To calculate the energy change using the equation Q = mc(triangle shaped symbol)T.
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When doing calculations with solutions, what do we assume?
That the solutions behave like water, this means that 1cm^3 of solution has a mass of 1g and the specific heat capacity of the solution is 4.2J/g degrees C.
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25cm^3 of dilute nitric acid is added to 25cm^3 of potassium hydroxide solution in a polystyrene cup. A temperature rise of 12 degrees C is recorded. What is the energy change?
Q = mc(triangle shape symbol)T. Volume of solution = 25+25=50cm. Energy change = 50x4.2x12 =2520J = 2.52kJ.
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When 50cm^3 of sulphuric acid was added to 100cm^3 of sodium hydroxide in a polystyrene cup the temperature increased y 12 degrees C. What is the energy change?
7560J or 7.56kJ.
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What do we assume when a solid is added to water or to an aqueous solution?
That the mass of the solution does not change, and also that 1cm^3 of solution has a mass of 1g and this its specific heat capacity is 4.2J/g degrees C.
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How can energy transfer that takes place during neutralisation and displacement reactions be calculated?
Using the equation Q = mc(triangle shaped symbol)T.
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When 5.6g of iron filings reacted completely with 200cm^3 of copper(II) sulphate solution the temperature of the solution increased by 17 degrees C. What is the energy change in kJ/mol of iron. (Relative atomic mass of Fe = 56)?
142.8kJ/mol of iron.
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Card 2

Front

When is energy transferred to or from a solution?

Back

When a reaction takes place in the solution.

Card 3

Front

Where is it best to do energy transfers in solutions to reduce energy transfers to the surroundings?

Back

Preview of the front of card 3

Card 4

Front

How can the temperature change of the solution be used?

Back

Preview of the front of card 4

Card 5

Front

When doing calculations with solutions, what do we assume?

Back

Preview of the front of card 5
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