# 4.4 Reaction yields  (Page 4/9)

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## Key concepts and summary

When reactions are carried out using less-than-stoichiometric quantities of reactants, the amount of product generated will be determined by the limiting reactant. The amount of product generated by a chemical reaction is its actual yield. This yield is often less than the amount of product predicted by the stoichiometry of the balanced chemical equation representing the reaction (its theoretical yield). The extent to which a reaction generates the theoretical amount of product is expressed as its percent yield.

## Key equations

• $\text{percent yield}=\left(\frac{\text{actual yield}}{\text{theoretical yield}}\right)\phantom{\rule{0.4em}{0ex}}×\phantom{\rule{0.2em}{0ex}}100$

## Chemistry end of chapter exercises

The following quantities are placed in a container: 1.5 $×$ 10 24 atoms of hydrogen, 1.0 mol of sulfur, and 88.0 g of diatomic oxygen.

(a) What is the total mass in grams for the collection of all three elements?

(b) What is the total number of moles of atoms for the three elements?

(c) If the mixture of the three elements formed a compound with molecules that contain two hydrogen atoms, one sulfur atom, and four oxygen atoms, which substance is consumed first?

(d) How many atoms of each remaining element would remain unreacted in the change described in (c)?

What is the limiting reactant in a reaction that produces sodium chloride from 8 g of sodium and 8 g of diatomic chlorine?

The limiting reactant is Cl2.

Which of the postulates of Dalton's atomic theory explains why we can calculate a theoretical yield for a chemical reaction?

A student isolated 25 g of a compound following a procedure that would theoretically yield 81 g. What was his percent yield?

$\text{Percent yield}=\text{31%}$

A sample of 0.53 g of carbon dioxide was obtained by heating 1.31 g of calcium carbonate. What is the percent yield for this reaction?

${\text{CaCO}}_{3}\left(s\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{CaO}\left(s\right)+{\text{CO}}_{2}\left(s\right)$

Freon-12, CCl 2 F 2 , is prepared from CCl 4 by reaction with HF. The other product of this reaction is HCl. Outline the steps needed to determine the percent yield of a reaction that produces 12.5 g of CCl 2 F 2 from 32.9 g of CCl 4 . Freon-12 has been banned and is no longer used as a refrigerant because it catalyzes the decomposition of ozone and has a very long lifetime in the atmosphere. Determine the percent yield.

$\text{g}\phantom{\rule{0.2em}{0ex}}{\text{CCl}}_{4}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{mol}\phantom{\rule{0.2em}{0ex}}{\text{CCl}}_{4}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{mol}\phantom{\rule{0.2em}{0ex}}{\text{CCl}}_{2}{\text{F}}_{2}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{g}\phantom{\rule{0.2em}{0ex}}{\text{CCl}}_{2}{\text{F}}_{2},$ $\text{percent yield}=\text{48.3%}$

Citric acid, C 6 H 8 O 7 , a component of jams, jellies, and fruity soft drinks, is prepared industrially via fermentation of sucrose by the mold Aspergillus niger . The equation representing this reaction is
${\text{C}}_{12}{\text{H}}_{22}{\text{O}}_{11}+{\text{H}}_{2}\text{O}+3{\text{O}}_{2}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}2{\text{C}}_{6}{\text{H}}_{8}{\text{O}}_{7}+4{\text{H}}_{2}\text{O}$

What mass of citric acid is produced from exactly 1 metric ton (1.000 $×$ 10 3 kg) of sucrose if the yield is 92.30%?

Toluene, C 6 H 5 CH 3 , is oxidized by air under carefully controlled conditions to benzoic acid, C 6 H 5 CO 2 H, which is used to prepare the food preservative sodium benzoate, C 6 H 5 CO 2 Na. What is the percent yield of a reaction that converts 1.000 kg of toluene to 1.21 kg of benzoic acid?

$2{\text{C}}_{6}{\text{H}}_{5}{\text{CH}}_{3}+3{\text{O}}_{2}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}2{\text{C}}_{6}{\text{H}}_{5}{\text{CO}}_{2}\text{H}+2{\text{H}}_{2}\text{O}$

$\text{percent yield}=\text{91.3%}$

In a laboratory experiment, the reaction of 3.0 mol of H 2 with 2.0 mol of I 2 produced 1.0 mol of HI. Determine the theoretical yield in grams and the percent yield for this reaction.

Outline the steps needed to solve the following problem, then do the calculations. Ether, (C 2 H 5 ) 2 O, which was originally used as an anesthetic but has been replaced by safer and more effective medications, is prepared by the reaction of ethanol with sulfuric acid.

2C 2 H 5 OH + H 2 SO 4 ⟶ (C 2 H 5 ) 2 + H 2 SO 4 ·H 2 O

What is the percent yield of ether if 1.17 L (d = 0.7134 g/mL) is isolated from the reaction of 1.500 L of C 2 H 5 OH
(d = 0.7894 g/mL)?

Convert mass of ethanol to moles of ethanol; relate the moles of ethanol to the moles of ether produced using the stoichiometry of the balanced equation. Convert moles of ether to grams; divide the actual grams of ether (determined through the density) by the theoretical mass to determine the percent yield; 87.6%

Outline the steps needed to determine the limiting reactant when 30.0 g of propane, C 3 H 8 , is burned with 75.0 g of oxygen.

Determine the limiting reactant.

Outline the steps needed to determine the limiting reactant when 0.50 mol of Cr and 0.75 mol of H 3 PO 4 react according to the following chemical equation.
$2\text{Cr}+2{\text{H}}_{3}{\text{PO}}_{4}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}2{\text{CrPO}}_{4}+3{\text{H}}_{2}$

Determine the limiting reactant.

The conversion needed is $\text{mol Cr}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{mol}\phantom{\rule{0.2em}{0ex}}{\text{H}}_{3}{\text{PO}}_{4}.$ Then compare the amount of Cr to the amount of acid present. Cr is the limiting reactant.

What is the limiting reactant when 1.50 g of lithium and 1.50 g of nitrogen combine to form lithium nitride, a component of advanced batteries, according to the following unbalanced equation?
$\text{Li}+{\text{N}}_{2}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{Li}}_{3}\text{N}$

Uranium can be isolated from its ores by dissolving it as UO 2 (NO 3 ) 2 , then separating it as solid UO 2 (C 2 O 4 )·3H 2 O. Addition of 0.4031 g of sodium oxalate, Na 2 C 2 O 4 , to a solution containing 1.481 g of uranyl nitrate, UO 2 (NO 3 ) 2 , yields 1.073 g of solid UO 2 (C 2 O 4 )·3H 2 O.

Na 2 C 2 O 4 + UO 2 (NO 3 ) 2 + 3H 2 O ⟶ UO 2 (C 2 O 4 )·3H 2 O + 2NaNO 3

Determine the limiting reactant and the percent yield of this reaction.

Na 2 C 2 O 4 is the limiting reactant. percent yield = 86.6%

How many molecules of C 2 H 4 Cl 2 can be prepared from 15 C 2 H 4 molecules and 8 Cl 2 molecules?

How many molecules of the sweetener saccharin can be prepared from 30 C atoms, 25 H atoms, 12 O atoms, 8 S atoms, and 14 N atoms? Only four molecules can be made.

The phosphorus pentoxide used to produce phosphoric acid for cola soft drinks is prepared by burning phosphorus in oxygen.

(a) What is the limiting reactant when 0.200 mol of P 4 and 0.200 mol of O 2 react according to ${\text{P}}_{4}+5{\text{O}}_{2}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{P}}_{4}{\text{O}}_{10}$

(b) Calculate the percent yield if 10.0 g of P 4 O 10 is isolated from the reaction.

Would you agree to buy 1 trillion (1,000,000,000,000) gold atoms for \$5? Explain why or why not. Find the current price of gold at http://money.cnn.com/data/commodities/ $\left(\text{1 troy ounce}=\text{31.1 g}\right)$

This amount cannot be weighted by ordinary balances and is worthless.

#### Questions & Answers

An atom or group of atoms bearing anelectrical charge such as the sodium and chlorine atoms in a salt solution.
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pls wat is periodic table
Prince
it's a list that shows the chemical element arranged according to their properties.
what is the chemical equation for ideal gas?
what's Boyle and gas law?
what's the meaning of this℃ in atomic table
wat are ions
Sinyene
What is periodic table
Table that shows the elements in order of their atomic number
Uzair
organization of everything known in the universe in groups and periods. The structure is based on increasing mass and reaction properties.
Kate
How to mix chemical
why the elements of group 7 are called Noble gases
they aren't. group 8 is the noble gasses. they are snobs that don't mix with others like nobles, they have full valence shells so they don't form bonds with other elements easily. nobles don't mingle with the common folk...
Jessica
the group 7elements are not the noble gases . according to modern periodic group 18 are called noble gases elements because their valence shell are completely field so that they can't gain or loss electron so they are not able to involve in any chemical reaction.
Leena
Group 7 element they are not noble gases they halogen and halogen mean salt formers
SIRAJO
what is chemistry
chemistry is the branch of science which deal with the composition of matter
SHEDRACK
chemistry is an organized way to think about matter
Kate
Chemistry is the branch of science that deals with the composition, properties and uses of matter
Bamgbose
The branch of science concerned with the substances of which matter is composed, the investigation of their properties and reactions, and the use of such reactions to form new substances.
Aminu
discuss the orbital stracture of the following methane,ethane,ethylene,acetylene
Why phosphurs in solid state have one atom but in gas state have four atoms
Are nuclear reactions both exothermic reactions and endothermic reactions or what?
to what volume must 8.32 NaOH be diluted to its analytical concentration 0.20 M
weight in mg 1.76 mole of I
Sheriza
the types of hydrocarbons
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Emmanuel
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Jessica
aliphatic and aromatic hydrocarbons
Osakue
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Ohanaka
saturated and unsaturated
Leena
aromatic hydrocarbon aliphatic hydrocarbon
SIRAJO
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SIRAJO
how can you determine the electronegativity of a compound or in molecules
when u move from left to right in a periodic table the negativity increases
reeza
Are you trying to say that the elctronegativity increases down the group and decreases across the period?
Ohanaka
yes and also increases across the period
reeza
for instance when you look at one group of elements in a periodic table electronegativity decreases when you go across the table electronegativity increases. hydrogen is more electronegative than sodium, potassium of that group. oxygen is more electronegative than carbon.
reeza
i hope we all know that organic compounds have carbon as their back bone
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Osakue
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hanna
what is the oxidation number of nitrogen, oxygen and sulphur
Osakue
5, -2 & -2
hanna
What is periodic table
SIRAJO
What is an atom?
is a smallest particle of a chemical element that can exist
Osakue
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Osakue
it is a substance that cannot be broken down into simpler units by any chemical reaction
An atom is the smallest part of an element dat can take part in chemical reaction.
Idris
an atom is the smallest part of an element that can take part in a chemical reaction nd still retain it chemical properties
Precious
Is the smallest particles of an element that take part in chemical reaction without been change
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