ChemicalReaction1

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Chemical Reactions

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This PG code shows how ask questions about chemical reactions.


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PG problem file Explanation

Problem tagging data

Problem tagging: 

DOCUMENT();

loadMacros(
"PGstandard.pl",
"PGunion.pl",
"MathObjects.pl",
"PGML.pl",
"contextReaction.pl",
"PGcourse.pl",
);

TEXT(beginproblem()); # uncomment
$showPartialCorrectAnswers = 1;

Initialization: Load contextReaction.pl. 

Context("Reaction");

@reactants = ();
@products = ();
	
$reactants[0] = Formula("2C_2H_6 + 7O_2");
$products[0]  = Formula("4CO_2 + 6H_2O");

$reactants[1] = Formula("6CO_2 + 6O_2");
$products[1] = Formula("C_6 H_12 O_6 + 6 O_2");

$reactants[2] = Formula("3 Ca Cl_2 + 2 Na_3 PO_4");
$products[2] = Formula("Ca_3 (PO_4)_2 + 6 Na Cl");

# variations on 2NaOH + MgCl_2 --> 2NaCl + Mg(OH)_2
$a = list_random('Li','Na','K');
$b = list_random('F','Cl','Br');

# Use ${b}_2 instead of $b_2 below so that Perl knows the 
# variable name is $b = ${b} and not $b_2 = ${b_2}.
$reactants[3] = Formula("2 $a OH + Mg ${b}_2"); 
$products[3] = Formula("2 $a $b + Mg (OH)_2");

$num_choices = $#reactants;

$i = random(0,$num_choices,1);

Setup: We create a couple of arrays @reactants and @products and fill them with some examples of balanced chemical equations. The second and third examples show that groupings, such as for (OH)_2 are necessary. The third example shows how you could randomize a chemical reaction question. In particular, note that ${b}_2 is needed instead of $b_2 so that Perl interprets the variable as $b with a subscript of 2 instead of a variable named $b_2 with no subscript. 

BEGIN_PGML
[` [$reactants[ $i ]] \longrightarrow `] [_____________________________]{$products[ $i ]}

Enter a subscript using an underscore, such as [| H_2 O |]* for [` \mathrm{H_2 O} `].
END_PGML

COMMENT('MathObject version.  Uses PGML.');
ENDDOCUMENT();

Main Text: Note that we uses spaces around $i in things like $reactants[ $i ] and $products[ $i ]. This is a work around for a known PGML bug as of June 2015 (the bug will likely get fixed very soon).

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