Chemistry Scoring Guidelines 2015 - College Board

AP Chemistry

2015 Scoring Guidelines

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1.0 g Na ?

1.0 mol Na 1.0 mol e?

= 0.043 mol e22.99 g Na 1.0 mol Na

1.0 g Ca ?

1.0 mol Ca 2.0 mol e?

= 0.050 mol e40.08 g Ca 1.0 mol Ca

catalyst

C2H5OH(g) ????

? C2H 4 (g) + H2O(g) DH298 = 45.5 kJ/molrxn ; DS298 = 126 J/(K mol rxn )

ethanol

ethene

water

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1 atm

760 torr

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n=

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(0.775 atm)(0.0854 L)

PV

=

= 0.00264 mol

RT

(0.08206 L atm mol -1 K -1 )(305 K)

% yield =

actual yield

0.00264 mol

¡Á 100 =

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maximum possible yield

0.00434 mol

DG298

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? ?? ? ?

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e

(

-DG ¡ã

)

RT

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