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Which of the following equations are balanced? Balance any that need it. (a) The thermite reaction, used in welding: $$ \mathrm{Al}+\mathrm{Fe}_{2} \mathrm{O}_{3} \longrightarrow \mathrm{Al}_{2} \mathrm{O}_{3}+\mathrm{Fe} $$ (b) The photosynthesis of glucose from \(\mathrm{CO}_{2}\) : $$ 6 \mathrm{CO}_{2}+6 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+6 \mathrm{O}_{2} $$ (c) The separation of gold from its ore: \(\mathrm{Au}+2 \mathrm{NaCN}+\mathrm{O}_{2}+\mathrm{H}_{2} \mathrm{O} \longrightarrow\) $$ \mathrm{NaAu}(\mathrm{CN})_{2}+3 \mathrm{NaOH} $$

Short Answer

Expert verified
(a) Not balanced: Correct as 2 Al + Fe鈧侽鈧 鈫 Al鈧侽鈧 + 2 Fe. (b) Balanced. (c) Not balanced: Correct as Au + 3 NaCN + O鈧 + 2 H鈧侽 鈫 NaAu(CN)鈧 + 3 NaOH.

Step by step solution

01

Check Balance - Thermite Reaction (a)

For the equation \( \mathrm{Al} + \mathrm{Fe}_{2} \mathrm{O}_{3} \longrightarrow \mathrm{Al}_{2} \mathrm{O}_{3} + \mathrm{Fe} \), we list the elements: Al, Fe, O. We have 1 Al on the left and 2 in Al鈧侽鈧 on the right, 2 Fe on the left and 1 on the right, and 3 O on both sides. This equation is unbalanced for both Al and Fe.
02

Balance Thermite Reaction (a)

We need to balance Al and Fe. Place a coefficient of 2 before Al on the left and 2 before Fe on the right. The balanced equation becomes \( 2 \mathrm{Al} + \mathrm{Fe}_{2} \mathrm{O}_{3} \rightarrow \mathrm{Al}_{2} \mathrm{O}_{3} + 2 \mathrm{Fe} \). Now, both Al and Fe are balanced.
03

Check Balance - Photosynthesis (b)

For the equation \( 6 \mathrm{CO}_{2} + 6 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} + 6 \mathrm{O}_{2} \), we have: 6 C and 12 H on both sides, and 18 O from CO鈧 and H鈧侽 on the left, matching 18 O on the right (6 in C鈧咹鈧佲倐O鈧, 12 in O鈧). This equation is balanced.
04

Check Balance - Gold Separation (c)

For the equation \( \mathrm{Au} + 2 \mathrm{NaCN} + \mathrm{O}_{2} + \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{NaAu(CN)}_{2} + 3 \mathrm{NaOH} \), count elements: 1 Au, 2 Na, 2 CN, and 5 O on the left compared to 1 Au, 2 CN, 3 Na, and 3 O on the right. This is unbalanced for Na and O.
05

Balance Gold Separation (c)

To balance Na and O, place 3 NaCN and 4 NaOH. Adjust oxygen with an extra H鈧侽 on the left. The balanced equation is: \( \mathrm{Au} + 3 \mathrm{NaCN} + \mathrm{O}_{2} + 2 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{NaAu(CN)}_{2} + 3 \mathrm{NaOH} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Thermite Reaction
The thermite reaction is a well-known metal oxidation reaction, which involves the reaction of aluminum (Al) with iron(III) oxide (Fe鈧侽鈧) to produce aluminum oxide (Al鈧侽鈧) and iron (Fe). This reaction is commonly used in welding, especially for joining railway tracks due to the intense heat produced.
Balancing the thermite reaction requires ensuring equal numbers of Al, Fe, and O atoms on both sides of the equation. Initially, one aluminum atom reacts with iron(III) oxide, but since we need two aluminum atoms in Al鈧侽鈧 on the product side, we adjust by placing a coefficient of 2 in front of Al.
  • This balances the aluminum.
  • The iron, which is initially balanced incorrectly with 2 Fe on the left, requires a factor of 2 on Fe to align with the reaction product side.
The balanced equation is:\[2 \mathrm{Al} + \mathrm{Fe}_{2} \mathrm{O}_{3} \rightarrow \mathrm{Al}_{2} \mathrm{O}_{3} + 2 \mathrm{Fe}\]This balance ensures that there are 2 Al, 2 Fe, and 3 O atoms on both sides, maintaining the law of conservation of mass.
Photosynthesis Equation
Photosynthesis is the critical biochemical process by which green plants, algae, and some bacteria convert light energy into chemical energy, stored in glucose. The general photosynthesis equation is:\[6 \mathrm{CO}_{2} + 6 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} + 6 \mathrm{O}_{2}\]It describes how carbon dioxide (CO鈧) and water (H鈧侽), in the presence of sunlight, are converted into glucose (C鈧咹鈧佲倐O鈧) and oxygen (O鈧). This balanced chemical equation reflects the conservation of atoms:
  • 6 carbon atoms on each side from CO鈧 and C鈧咹鈧佲倐O鈧
  • 12 hydrogen atoms from H鈧侽 and C鈧咹鈧佲倐O鈧
  • 18 oxygen atoms contributed by CO鈧, H鈧侽, and produced as O鈧
This balance is crucial in illustrating how plants produce glucose, their energy source, and oxygen, a byproduct vital for life on earth.
Gold Separation Process
The gold separation process, also known as gold cyanidation, involves extracting gold from its ore using a solution of sodium cyanide (NaCN). This process involves the chemical reaction between gold (Au), sodium cyanide, oxygen (O鈧), and water (H鈧侽) to form sodium gold cyanide \(\mathrm{NaAu(CN)}_{2}\) and sodium hydroxide (NaOH).The unbalanced equation is:\[\mathrm{Au} + 2 \mathrm{NaCN} + \mathrm{O}_{2} + \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{NaAu(CN)}_{2} + 3 \mathrm{NaOH}\]Balancing this equation aligns the quantity of each element on both sides:
  • Adjust the quantity of sodium: Change to 3 NaCN and 3 NaOH
  • Balance oxygen with an extra molecule: Add another H鈧侽 on the left
The balanced equation becomes:\[\mathrm{Au} + 3 \mathrm{NaCN} + \mathrm{O}_{2} + 2 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{NaAu(CN)}_{2} + 3 \mathrm{NaOH}\]This process efficiently extracts gold by ensuring that the gold atoms are entirely converted into soluble complexes, allowing them to be separated easily from the ore.

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Most popular questions from this chapter

Sodium azide \(\left(\mathrm{NaN}_{3}\right)\) yields \(\mathrm{N}_{2}\) gas when heated to \(300{ }^{\circ} \mathrm{C}\), a reaction used in automobile air bags. If \(1.00 \mathrm{~mol}\) of \(\mathrm{N}_{2}\) has a volume of \(47.0 \mathrm{~L}\) under the reaction conditions, how many liters of gas can be formed by heating \(38.5 \mathrm{~g}\) of \(\mathrm{NaN}_{3} ?\) The reaction is $$ 2 \mathrm{NaN}_{3}(s) \longrightarrow 3 \mathrm{~N}_{2}(g)+2 \mathrm{Na}(s) $$

Sodium borohydride, \(\mathrm{NaBH}_{4}\), a substance used in the synthesis of many pharmaceutical agents, can be prepared by reaction of NaH with \(\mathrm{B}_{2} \mathrm{H}_{6}\) according to the equation \(2 \mathrm{NaH}+\mathrm{B}_{2} \mathrm{H}_{6} \longrightarrow 2 \mathrm{NaBH}_{4}\) (a) How many grams of \(\mathrm{NaBH}_{4}\) can be prepared by reaction between \(8.55 \mathrm{~g}\) of \(\mathrm{NaH}\) and \(6.75 \mathrm{~g}\) of \(\mathrm{B}_{2} \mathrm{H}_{6} ?\) (b) Which reactant is limiting, and how many grams of the excess reactant will be left over?

Draw a molecular representation of reactants and products for the following reaction, which plays a significant role in atmospheric pollution. Nitrogen monoxide reacts with oxygen to produce nitrogen dioxide. Represent each atom as a sphere labeled with the elemental symbol \(\mathrm{N}\) or \(\mathrm{O}\). Make sure that your drawing represents a balanced chemical reaction.

The molar mass of \(\mathrm{HCl}\) is \(36.5 \mathrm{~g} / \mathrm{mol}\), and the average mass per \(\mathrm{HCl}\) molecule is \(36.5 \mathrm{u}\). Use the fact that \(1 \mathrm{u}=1.6605 \times 10^{-24} \mathrm{~g}\) to calculate Avogadro's number.

An unknown liquid is composed of \(5.57 \% \mathrm{H}, 28.01 \% \mathrm{Cl}\), and \(66.42 \%\) C. The molecular weight found by mass spectrometry is \(126.58\). What is the molecular formula of the compound?

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