All GRE Subject Test: Chemistry Resources
Example Questions
Example Question #11 : Reaction Chemistry
If of is used for the reaction given, how many grams of was formed?
Based on the molecular equation, for every 4 moles of reacted, 2 moles of is formed as a product:
We must calculate the molecular weight of :
To calculate the number of grams of , we need to convert the number of moles of to grams using the molecular weight as a conversion factor.
Example Question #12 : Reaction Chemistry
If of is formed during the reaction given, how many grams of was used?
Based on the molecular equation, for every 2 moles of formed, 1 mole of is reacted:
We must calculate the molecular weight of :
To calculate the number of grams of , we need to convert the number of moles of to grams using the molecular weight as a conversion factor.
Example Question #13 : Reaction Chemistry
If of is formed during the reaction given, how many grams of was used?
Based on the molecular equation, for every 3 moles of formed, 1 mole of is reacted:
We must calculate the molecular weight of :
To calculate the number of grams of , we need to convert the number of moles of to grams using the molecular weight as a conversion factor.
Example Question #1 : Oxidation Reduction Reactions
Based on the chemical equation given, which of the following compounds underwent reduction?
The type of chemical reaction given is called an oxidation-reduction reaction. In this type of reaction, there is a transfer of electrons from one element to another. The species gaining an electron is said to be reduced and the species losing an electron is oxidized. Manganese ion goes from a to a oxidation state. Therefore, manganese is reduced in the chemical reaction because it gains electrons from the compound being oxidized (iron).
Example Question #1 : Principles Of Oxidation Reduction Reactions
Methane combusts in the presence of oxygen according to the following reaction:
Which of the following statements is true concerning the reaction?
will be the limiting reagent
Oxygen has a charge of throughout the entire reaction
Carbon has an initial oxidation state of
Oxygen is oxidized in the reaction
Carbon is oxidized in the reaction
Carbon is oxidized in the reaction
By comparing the oxidation number of an atom as a reactant and its oxidation number as a product, we can determine if the atom has been oxidized or reduced. In increase in oxidation number indicates a loss of electrons, or oxidation. A decrease in oxidation number signals a gain of electrons, or reduction.
For electrochemistry, you should familiarize yourself with the traditional oxidation states of hydrogen , halogens , oxygen , and elemental atoms .
Carbon is initially in the form of methane, meaning that it is attached to four hydrogen atoms. The molecule is neutral, and each hydrogen has an oxidation number of . Carbon must have an initial oxidation state of in order to balance the molecular charge.
In the a product, carbon is attached to two oxygens, each with a charge of . Again, the molecule is neutral, so carbon must balance these charges. This means that carbon's final oxidation state is .
Since carbon went from an oxidation state of to , we can conclude that carbon has been oxidized in the reaction.
Example Question #1 : Reactions With Inorganic Compounds
What happens when a solution of is added to a solution of ?
A synthesis reaction
A combustion reaction
A double displacement reaction
A combination reaction
A decomposition reaction
A double displacement reaction
The chemical reaction that would occur is provided below:
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 switch places to form two new products.
Example Question #2 : Reactions With Inorganic Compounds
Which of the following types of reactions best describes the following reaction:
Catalytic
Combustion
Alkylation
Synthesis
Combustion
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.
Example Question #3 : Reactions With Inorganic Compounds
For the reaction given, identify the type of reaction taking place.
Synthesis reaction
Combination reaction
Displacement reaction
Decomposition reaction
Displacement reaction
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, ion moves from to to form .
Example Question #3 : Reactions With Inorganic Compounds
Determine the percentage yield of the reaction given if 12.6 grams of is reacted excess to give 10.4 grams of .
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 to moles:
Based on the chemical equation 1 mole of is produced for every 1 mole of reacted.
Convert the moles of to grams:
Example Question #4 : Reactions With Inorganic Compounds
Determine the percentage yield of the reaction given if 21.0 grams of is reacted with excess to give 10.2 grams of .
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 to moles:
Based on the chemical equation 1 mole of is produced for every 1 mole of reacted.
Convert the moles of to grams: