how you calculate stoichiometry?
for this question please read this one!
for this question please read this one!
The word stoichiometry is originated from the Greek word
stoicheion meaning elementary constituent, and metrin relates to measuring.
Stoichiometry involves quantitative calculations of reactants and products in
chemical reactions. It’s based on the law of conservation of mass where the
total mass of reactants is equal to the total mass of the products. Stoichiometry
is founded on the law of conservation of mass where the total mass of the
reactants = total mass of the products. The amount of product can easily
be calculated if the amounts of the separate reactants are known.
CH4 + 2 O2 → CO2 + 2 H2O
Here, One molecule of methane (CH4) reacts with 2 molecules of
Oxygen gas to achieve 2 molecules of CO2 and two molecules of water. The
quantitative relationship here is measured by the Stoichiometry and also used
to find out the amount of reactants that are yield in a given reaction.
Solved Examples
Example 1 Ammonia reacts with solid copper oxide and
releases nitrogen gas, solid copper and water vapour. Write this chemical
reaction and balance the equation according to its stoichiometry.
Solution: The above example can be written
as
NH3 + CuO —> Cu + H2O
+ N2
Balanced equation based
on its stoichiometry,
2NH3 + 3CuO —> 3Cu +
3H2O + N2
Example 2 Sulphur trioxide gas is released on combustion
of iron pyrites(FeS2). Describe the chemical reaction and balance the equation
based on stoichiometry of every compound.
Solution: The chemical reaction for the above example is
Solution: The chemical reaction for the above example is
FeS2 + O2 —> Fe2O3 +
SO3
Combustion compounds react with oxygen.
The balanced chemical equation based on its stoichiometry is
The balanced chemical equation based on its stoichiometry is
4FeS2 + 15O2 —> 2Fe2O3 + 8SO3
Stoichiometry Problems
When we carry out a
reaction in either an industrial setting or a laboratory, it is easier to work
with masses of substances than with the numbers of molecules or moles.
The general method for converting from the mass of any reactant or product to
the mass of any other reactant or product using a balanced chemical equation is
outlined in and described in the following text.
Steps in Converting between Masses of Reactant and Product
- Convert the mass of one substance (substance A) to the corresponding number of moles using its molar mass.
- From the balanced chemical equation, obtain the number of moles of another substance (B) from the number of moles of substance A using the appropriate mole ratio (the ratio of their coefficients).
- Convert the number of moles of substance B to mass using its molar mass. It is important to remember that some species are in excess by virtue of the reaction conditions. For example, if a substance reacts with the oxygen in air, then oxygen is in obvious (but unstated) excess.
Converting
amounts of substances to moles—and vice versa—is the key to all stoichiometry
problems, whether the amounts are given in units of mass (grams or kilograms),
weight (pounds or tons), or volume (liters or gallons).
Figure 1. A Flowchart for Stoichiometric Calculations Involving Pure
Substances
The molar masses of the reactants and the products are used
as conversion factors so that you can calculate the mass of product from the
mass of reactant and vice versa.To illustrate this procedure, let’s return to
the combustion of glucose. We saw earlier that glucose reacts with oxygen to
produce carbon dioxide and water:
Equation 1.
C6H12O6(s) + 6O2(g)
→ 6CO2(g) + 6H2O(l)
Just before a
chemistry exam, suppose a friend reminds you that glucose is the major fuel
used by the human brain. You therefore decide to eat a candy bar to make sure
that your brain doesn’t run out of energy during the exam (even though there is
no direct evidence that consumption of candy bars improves performance on
chemistry exams). If a typical 2 oz candy bar contains the equivalent of 45.3 g
of glucose and the glucose is completely converted to carbon dioxide during the
exam, how many grams of carbon dioxide will you produce and exhale into the
exam room?
The initial
step in solving a problem of this type must be to write the balanced chemical
equation for the reaction. Inspection of shows that it is balanced as written,
so we can proceed to the strategy outlined in , adapting it as follows:
1.
Use the molar mass of
glucose (to one decimal place, 180.2 g/mol) to determine the number of moles of
glucose in the candy bar:
2.
Use the molar mass of
CO2 (44.010 g/mol) to calculate the mass of CO2
corresponding to 1.51 mol of CO2:
3 3. We can summarize these
operations as follows:
Discrepancies
between the two values are attributed to rounding errors resulting from using
stepwise calculations in steps 1–3.
what the goal we learn stoichionetry?
BalasHapusone of the goal is Applying In Charging Battery.
HapusIs there any evect of reactant in chemical reaction?
BalasHapusdepend on what kind of the reactions.
HapusCan you give me more example about stoikiometry in dayly life?
BalasHapusCalorimeter
Hapusboil water
Capillarity in water
Charging battery
What is the different between gay lusac law and avogadro?
BalasHapusThis relationship between temperature and pressure is known as Gay-Lussac's law. It states that if the volume of a container is held constant as the temperature of a gas increases, the pressure inside the container will also increase. As with the other gas laws, this one can be represented in the form of an equation:
HapusP1/T1 = P2/T2
Avogadro’s law, a statement that under the same conditions of temperature and pressure, equal volumes of different gases contain an equal number of molecules. This empirical relation can be derived from the kinetic theory of gases under the assumption of a perfect (ideal) gas. The law is approximately valid for real gases at sufficiently low pressures and high temperatures
What the different Mass molecul relativ (Mr) and Mass?
BalasHapusThe molar mass of a compound tells you the mass of 1 mole of that substance. In other words, it tells you the number of grams per mole of a compound. The units for molar mass are, therefore, grams/mole.
HapusAn atomic mass is unit less and defined as precisely 1/12 the mass of an atom of carbon-12 not in motion. The carbon-12 (C-12) atom has six protons and six neutrons in its nucleus and it's atomic mass is exactly 12 by definition
On your blog there is said about quantitative calculations of reactants and products in chemical reactions based on mass conservation law. Can you explain about the law of mass conservation ???
BalasHapusI often wonder how to find Ar. So give me an example to look for Ar if that is known is Mr.?
BalasHapus