GRE Subject Test: Chemistry - Reactions with Inorganic Compounds

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For the reaction given, identify the type of reaction taking place.

Displacement reaction

Combination reaction

Decomposition reaction

Synthesis reaction

Explanation

A displacement reaction is one in which an atom, ion or molecule moves from one compound to another to replace an atom, ion or molecule in another compound. In the reaction given, $SO_{4}^{2-}$ ion moves from $CuSO_{4}$ to to form $ZnSO_{4}$ .

Which of the following types of reactions best describes the following reaction:

$C_{3}H_{8}\ +\ 5O_{2}\rightarrow\ 3CO_{2}\ +\ 4H_{2}O$

Combustion

Catalytic

Synthesis

Alkylation

Explanation

The type of reaction given is termed a combustion reaction. A combustion reaction is one that involves a substance reacting with molecular oxygen. For combustion reactions involving a hydrocarbon as given in the example, the major products are carbon dioxide and water. The word combustion is a synonym for burn.

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For the reaction given, identify the type of reaction taking place.

Displacement reaction

Decomposition reaction

Combination reaction

Synthesis reaction

Explanation

A displacement reaction is one in which an atom, ion or molecule moves from one compound to another to replace an atom, ion or molecule in another compound. In the reaction given, 2 $Cl^{-}$ ions move from 2 moles of to to form $CuCl_{2}$ .

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Determine the percentage yield of the reaction given if 12.6 grams of $Ba(NO)_{3}$ is reacted excess $Na_{2}SO_{4}$ to give 10.4 grams of $BaSO_{4}$ .

Explanation

In chemistry, percentage yield is a term used to quantify the efficiency of a chemical reaction. In order to calculate this quantity, the value for the actual yield and theoretical yield is needed. The actual yield is the amount of product obtained during a chemical reaction. The theoretical yield is the maximum amount of product possible to be obtain by a chemical reaction which is based on the amount of reactants used. Below is the formula needed to calculate the percentage yield.

Convert the number of grams of $Ba(NO_{3})_{2}$ to moles:

$12.6 g\ Ba(NO_{3})_{2}\times \frac{mole}{261.37g}=0.0482\ moles\ Ba(NO_{3})_{2}$

Based on the chemical equation 1 mole of $BaSO_{4}$ is produced for every 1 mole of $Ba(NO_{3})_{2}$ reacted.

$moles\ of Ba(NO_{3})_{2}=moles\ of\ BaSO_{4}$

Convert the moles of $BaSO_{4}$ to grams:

$0.0482\ moles\ BaSO_{4} \times\ \frac{233.43g}{moles}=11.3g\ BaSO_{4}$

$Percentage\ Yield =\frac{actual\ yield}{theoretical\ yield}\times100$

$Percentage\ Yield =\frac{10.4g}{11.3g}\times100=92.0 %$

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Determine the percentage yield of the reaction given if 40.0 grams of $CaCO_{3}$ is heated to give 15.0 grams of .

Explanation

Convert the number of grams of $CaCO_{3}$ to moles:

$40.0 g\ CaCO_{3}\times \frac{mole}{100.09g}=0.3996\ moles\ CaCO_{3}$

Based on the chemical equation 1 mole of is produced for every 1 mole of $CaCO_{3}$ reacted.

$moles\ of\ CaCO_{3}=moles\ of\ CaO$

Convert the moles of to grams:

$0.3996\ moles\ \times\ \frac{56.08g}{moles}=22.0g\ CaO$

$Percentage\ Yield =\frac{actual\ yield}{theoretical\ yield}\times100$

$Percentage\ Yield =\frac{15.0g}{22.0g}\times100=68.2 %$

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Determine the percentage yield of the reaction given if 21.0 grams of is reacted with excess to give 10.2 grams of .

Explanation

Convert the number of grams of to moles:

$21.0 g\ NaOH\times \frac{mole}{40.0g}=0.525\ moles\ NaOH$

Based on the chemical equation 1 mole of is produced for every 1 mole of reacted.

$moles\ of\ NaOH=moles\ of\ NaCl$

Convert the moles of to grams:

$0.525\ moles\ \times\ \frac{58.44g}{moles}=30.7g\ NaCl$

$Percentage\ Yield =\frac{actual\ yield}{theoretical\ yield}\times100$

$Percent\ Yield =\frac{10.2g}{30.7g}\times100=33.2 %$

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Determine the theoretical yield in grams of $Al_{2}(SO_{4})_{3}$ produced if 5.6 grams of $Al(OH)_{3}$ is reacted with excess $H_{2}SO_{4}$ .

Explanation

Convert the number of grams of $Al(OH)_{3}$ to moles:

$5.6 g\ Al(OH)_{3}\times \frac{mole}{78.00g}=0.0718\ moles\ Al(OH)_{3}$

Based on the chemical equation 1 mole of $Al_{2}(SO_{4})_{3}$ is produced for every 2 mole of $Al(OH)_{3}$ reacted.

$2\ moles\ of Al(OH)_{3}=1\ mole\ of\ Al_{2}(SO_{4})_{3}$

Therefore: $0.0718\ moles\ Al(OH)_{3}\times \frac{1\ moles\ Al_{2}(SO_{4})_{3}}{2\ moles\ Al(OH)_{3}}=0.0359\ moles\ Al_{2}(SO_{4})_{3}$

Convert the moles of $Al_{2}(SO_{4})_{3}$ to grams:

$0.0359\ moles\ Al_{2}(SO_{4})_{3} \times\ \frac{342.15g}{moles}=12.3g\ Al_{2}(SO_{4})_{3}$

What happens when a solution of is added to a solution of ?

A double displacement reaction

A synthesis reaction

A combination reaction

A decomposition reaction

A combustion reaction

Explanation

The chemical reaction that would occur is provided below:

$AgNO_{3(aq)}+NaCl_{(aq)}\rightarrow NaNO_{3(aq)} + AgCl_{(s)}$

This type of reaction is called a double displacement reaction in which there is an exchange of ions between two compounds. This type of reaction usually results in the formation of a precipitate or gas. In terms of the positive ions, the $Ag^{+}$ switch places $Na^{+}$ to form two new products.

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For the reaction given, identify the type of reaction taking place.

Double displacement reaction

Synthesis reaction

Combination reaction

Decomposition reaction

Explanation

A displacement reaction is one in which an atom, ion or molecule moves from one compound to another to replace an atom, ion or molecule in another compound. In the reaction given, $NO_{3}^{-}$ ion moves from $AgNO_{3}$ to $Na_{2}CO_{3}$ . Also, $CO_{3}^{2-}$ ion moves from $Na_{2}CO_{3}$ to $AgNO_{3}$ .

Reactions with Inorganic Compounds

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