CHEMICAL EQUATIONS AND REACTIONS

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CHEMICAL EQUATIONS AND REACTIONS
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Chemical Equations and Reactions Elements - pure
substances that cannot be broken down into other
substances Represented by chemical symbols.
Examples are Ca, Br, H, C, Mg Compounds are
homogeneous substances made up of two or more
elements chemically bonded. Examples are NaCl,
KBr, F2, H2O
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Chemical equations represent what takes place in
a chemical reaction. Reactants are the
substances that exist before a chemical reaction
takes place and are to the left of the arrow or
yield sign. Products are what is produced and
they are located to the right of the yield sign.
Reactants ? Products Example Chlorine gas
plus Sodium bromide react to form Bromine gas
plus Sodium chloride. Cl2(g) NaBr(s) ?
Br2(g) NaCl(s)
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Is the chemical equation balanced? Did you
create or destroy matter? Cl2 NaBr ? Br2
NaCl Balance eq. by using coefficients(large
whole numbers placed before the element or
compound) The products and reactants are
multiplied by the coefficients YOU place. The
same number and kind of atoms must be present on
both the reactants and products side of the
equation. To correct this add a coefficient of 2
in front of NaCl in the product and coefficient
of 2 in front of NaBr in the reactant.
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Cl2 NaBr ? Br2 2NaCl
By adding a coefficient of 2 the Chlorine atoms
are now balanced. The next step would take a
look at the Sodium atoms. To balance the Sodium
atoms add a coefficient of 2 in front of the
NaBr. After adding the coefficients you should
see that there are 2 Bromine atoms on each side
of the equation. If you examine the final
equation all atoms are balanced. Cl2 2NaBr
? Br2 2NaCl ?Question?- Why cant you just
change the subscript?
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Balancing Equations Balance each equation if
necessary a. N2(g) H2(g) ? NH3 (g) b.
CaCO3 (s) ? CaO (s) CO2 (g) c. Se (s)
O2(g) ? SeO3 (g)
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Answers a. N2(g) 3 H2(g) ? 2 NH3 (g),
Synthesis b. CaCO3 (s) ? CaO (s) CO2 (g),
c. 2 Se (s) 3 O2(g) ? 2 SeO3 (g),