Chemistry 105 Exam 3 Homework
How many moles of oxygen gas react when a mole of methane undergoes complete combustion?Do not include units in your answer.
2 mol. Explanation: The complete balanced equation for the combustion reaction of methane is as follows: CH4+2O2→CO2+2H2O. Thus, 2 mol of oxygen gas reacts with 1 mol of methane (CH4).
Write the balanced equation for the complete combustion of 3-ethyl-2-methylpentane.
2C8H18+25O2⟶16CO2+18H2O. Explanation: 3-ethyl-2-methylpentane is a branched alkane, so the molecular formula follows the pattern CnH2n+2. From the prefix "pent-," it has a 5-carbon parent chain. It has 2 more carbons from the ethyl substituent and 1 more carbon from the methyl substituent, for a total of 8 carbons, and therefore 18 hydrogens. Combustion reactions are reactions with oxygen (O2) to give water (H2O) and carbon dioxide (CO2).
A linear alkane with 10 hydrogen atoms contains how many carbon atoms? Report your answer as an integer (whole number) without any decimal places. Do not include units in your response.
4. Explanation: The general formula for linear alkanes is CnH2n+2. If an alkane has 10 hydrogen atoms, we can solve for n: 2(n)+2=10, so the alkane has n=4 carbon atoms.
Choose the options below that are characteristics unique to aldehydes. Select all that apply: A. They can be used for preserving tissue species, embalming bodies, and sterilizing materials. B. They each contain a functional group with the structure −CHO. C. They are named using the suffix -al. D. They are named using the suffix -one.
A, B, and C. Explanation: Aldehydes each contain a carbonyl group bonded to two hydrogen atoms or a hydrogen atom and a carbon substituent, which is represented with the structure −CHO. They are named using the suffix -al. A common aldehyde is formaldehyde (also known as methanal), which is used to preserve the bodies of animals prior to dissection.
A fully saturated hydrocarbon is called an ______. Select the correct answer below: A. alkane B. alkene C. alkyne D. none of the above
A. alkane. Explanation: An alkane has only single covalent bonds between the carbon atoms, and contains the maximum number of hydrogens allowed for a hydrocarbon of that particular number of carbons. Therefore, alkanes are considered to be fully saturated.
How can hydrocarbons be classified? Select the correct answer below: A. by the types of bonds between carbon atoms B. by the types of bonds to hydrogen C. by the types of bonds to oxygen D. none of the above
A. by the types of bonds between carbon atoms. Explanation: Hydrocarbons are organic molecules that contain only hydrogen and carbon atoms. Carbon-carbon bonds can be single, double, or triple bonds, or part of an aromatic structure. Hydrogen can only form single bonds.
Which of the following is an example of a saturated hydrocarbon? Select the correct answer below: A. octane B. ethene C. benzene D. propyne
A. octane. Explanation: Octane is an alkane. Alkanes are hydrocarbons that contain only single bonds so they have the maximum number of hydrogen atoms bonded to carbon atoms and therefore are unsaturated.
An alkyl group attached to a carbon parent chain is called a ____. Select the correct answer below: A. substituent B. budding group C. branched group D. none of the above
A. substituent
Which of the following is an alcohol functional group? Select the correct answer below: A. −OH B. −SH C. −NH D. −COOH
A. −OH. Explanation: Alcohols are derivatives of hydrocarbons in which a hydroxyl, also called a hydroxy group, (an oxygen attached to a hydrogen, shown as -OH or HO- , has replaced a hydrogen atom. Alcohols are covalent molecules; the -OH group in an alcohol molecule is attached to a carbon atom by a covalent bond.
An acyclic (not a ring) hydrocarbon with the molecular formula CnH2n must be which type of hydrocarbon? Select the correct answer below: A. alkane B. alkene C. alkyne D. aromatic hydrocarbon
B. alkene. Explanation: The chemical formula of the form CnH2nis two fewer hydrogens than a saturated acyclic hydrocarbon, so it means there is a single double bond. This can only be the molecular formula of an alkene.
What name will be used to describe an alkane that has 4 carbon atoms in its longest continuous chain? Select the correct answer below: A. propane B. butane C. pentane D. hexane
B. butane
Alcohols are _______. Select the correct answer below: A. hydrocarbons B. derivatives of hydrocarbons C. acids D. derivatives of acids
B. derivatives of hydrocarbons
Which of the following provides the most descriptive picture of carbon atom orientation an alkane? Select the correct answer below: A. expanded formula B. skeletal structure C. condensed formula D. none of the above
B. skeletal structure. Explanation: The skeletal structure of an alkane shows the connectivity of all of the carbons it contains, and best reflects the geometry of the molecule in two dimensions. The hydrogens attached to each carbon are implied, not drawn. However, there is no ambiguity in the number or placement of the hydrogens, as these can be filled in logically based on the fact that each carbon must have an octet.
The names for aldehyde compounds include the class-identifying suffix _______. Select the correct answer below: A. -ol B. -ane C. -al D. -one
C. -al
What type of alkane does not follow the CnH2n+2 formula? Select the correct answer below: A. Linear alkanes B. Branched alkanes C. Cyclic alkanes D. All alkanes follow the formula
C. Cyclic alkanes. Explanation: Cyclic alkanes have the formula CnH2n, while all other alkanes follow the formula CnH2n+2.
Which of the following is not a characteristic of alcohols? Select the correct answer below: A. They are organic compounds. B. Their names always contain the suffix -ol. C. Each contains the functional group −O− attached to hydrogen atoms via single bonds. D. They contain only covalent bonds.
C. Each contains the functional group −O− attached to hydrogen atoms via single bonds. Explanation: Alcohols are organic derivatives of hydrocarbons in which an −OH group has replaced a hydrogen atom. This functional group is attached to a carbon atom by a single covalent bond. The names of alcohols contain the suffix -ol.
If multiple different substituents are present in the same molecule, they will be listed in_______. Select the correct answer below: A. order of decreasing mass B. order of increasing mass C. alphabetical order D. chronological order, according to their placement on the chain
C. alphabetical order
A benzene ring with an amino group as a substituent is called which of the following? Select the correct answer below: A. phenol B. benzoic acid C. aniline D. benzaldehyde
C. aniline
Alkanes can be represented by ______. Select the correct answer below: A. Lewis dot structures B. ball-and-stick models C. space-filling models D. all of the above
D. all of the above
Identify the nonmetals that are common in organic compounds. Select the correct answer below: A. hydrogen B. carbon C. oxygen D. all of the above
D. all of the above
As the molecular mass of an alkane increases, ________. Select the correct answer below: A. the melting points of alkanes steadily increase B. the molar mass of the alkane increases C. the boiling points of alkanes steadily increase D. all of the above
D. all of the above. Explanation: The number of carbon atoms present in an alkane has no limit. Increasing numbers of carbons in alkanes lead to stronger intermolecular attractions. Properties such as melting point and boiling point, which are directly related to intermolecular attractions, typically correlate well with number of carbons in the alkane.
Which of the following is an example of unsaturated hydrocarbon? Select the correct answer below: A. methane B. ethane C. propane D. ethene
D. ethene. Explanation: Saturated hydrocarbons are those with the maximum number of hydrogens for the carbon backbone, and unsaturated hydrocarbons have fewer hydrogens due to the presence of double and triple bonds. Ethene (C2H4) is an alkene, meaning it has a double bond, so it is unsaturated. The remaining choices are all alkanes and therefore saturated.
Which fragment would be listed first when naming a molecule? Select the correct answer below: A. trimethyl B. dipropyl C. ethyl D. tetrachloro
D. tetrachloro. Explanation: We ignore prefixes when determining which substituent will be listed first in naming a molecule. Substituents are listed in alphabetical order, so "tetrachloro" would come first, as "chloro" occurs first alphabetically.
Which is a possible product for the chlorination of methane? Select the correct answer below: A. chloromethane B. dichloromethane C. trichloromethane D. tetrachloromethane E. all of the above
E. all of the above
The melting point of two compounds are as follows: Benzaldehyde's melting point is −26∘C and barium chloride's is 962∘C. Identify which are likely to be organic and inorganic compounds from these values. Select the correct answer below: a. Benzaldehyde is more likely to be an organic compound because it has a low melting point. Barium chloride is likely to be inorganic because it has a high melting point. b. Benzaldehyde is more likely to be an inorganic compound because it has a low melting point. Barium chloride is likely to be organic because it has a high melting point. c. Both have very high melting points, so they are both likely to be organic. d. Both have very high melting points, so they are both likely to be inorganic.
a. Benzaldehyde is more likely to be an organic compound because it has a low melting point. Barium chloride is likely to be inorganic because it has a high melting point. Explanation: The melting point of benzaldehyde is low, and it is an organic compound. The boiling point of barium chloride is high, and is made of a metal and a nonmetal so it is an inorganic compound.
Which of the following is the formula for the simplest alkane, methane? Select the correct answer below: a. CH4 b. CH2 c. C2H4 d. C2H6
a. CH4. Explanation: Methane, CH4, is the simplest alkane. The simplest alkane contains one carbon atom and four hydrogen atoms to complete the octet.
Linear alkanes all have the formula_____. Select the correct answer below: a. CnH2n+2 b. CnH2n c. CnHn+2 d. CnHn
a. CnH2n+2. Explanation: If a linear alkane has n carbons, it must have precisely 2n+2 hydrogens.
Alkenes have the formula __________. Select the correct answer below: a. CnHn b. CnH2n c. CnH2n+2 d. CnH2n−2
b. CnH2n
Branched chain alkanes have the formula_____. Select the correct answer below: a. CnH2n b. CnH2n+2 c. CnH2n-2 d. CnHn+2
b. CnH2n+2. Explanation: Noncyclic alkanes all have the formula CnH2n+2, since alkanes have all single bonds they must have this formula in order for each carbon atom to have four bonds.
Identify the correct statements regarding the melting points of iron (II) sulfide (FeS) and methanol (CH3OH). Select the correct answer below: a. The melting point of iron (II) sulfide is low and the melting point of methanol is high. b. The melting point of iron (II) sulfide is high and the melting point of methanol is low. c. Both have the same melting points.
b. The melting point of iron (II) sulfide is high and the melting point of methanol is low. Explanation: Iron (II) sulfide is an inorganic compound since it contains a metal and a nonmetal. Methanol is an organic compound since it contains carbon, hydrogen, and oxygen. The melting point of inorganic compounds are generally higher than that of organic compounds because of strong ionic bonding.
Which of the following alkanes is unbranched? Select the correct answer below: a. Methylpropane b. n-Butane c. Isopentane d. Neopentane
b. n-Butane. Explanation: Alkanes with the prefix normal or n refer to a chain of carbon atoms with no branching.
Which of the following is a characteristic of alkanes? Select the correct answer below: a. Noncyclic alkanes have the molecular formula CnHn+1. b. The bond angles in some of their carbon chains are 180∘. c. Each of their carbon atoms is bonded to four other atoms. d. They have delocalized alternating carbon-carbon single and double bonds.
c. Each of their carbon atoms is bonded to four other atoms. Explanation: Alkanes are molecules consisting of only carbon and hydrogen atoms that have only single (σ) bonds. Each of their carbon atoms has sp3 hybrid orbitals, creating bond angles of approximately 109.5∘ and a zigzag shape when linked in a chain. Each carbon is bonded to four other atoms. Noncyclic alkanes have the molecular formula CnH2n+2. Alkanes are saturated hydrocarbons, the least reactive of the hydrocarbons, but they do burn in the presence of oxygen.
Propane (C3H8) is a common hydrocarbon fuel for outdoor grills. Given the chemical equation for its combustion, how many moles of oxygen (O2) are required for the complete combustion of 2 moles of propane? C3H8+5O2→3CO2+4H2O. Select the correct answer below: a. 6 b. 5 c. 8 d. 10
d. 10. Explanation: In the balanced equation, 5 moles of oxygen are required for the complete combustion of each mole of propane. Thus, 10 moles of oxygen will be required for the complete combustion of two moles of propane.
Identify the correct statement regarding the properties of inorganic compounds. Select the correct answer below: a. Inorganic compounds are typically polar or ionic. b. Inorganic compounds are often soluble in water. c. Inorganic compounds are rarely soluble in water. d. both A and B
d. both A and B. Explanation: norganic compounds are typically polar or ionic and since water is a polar compound inorganic molecules tend to be soluble in water. Where as organic compounds tend to be nonpolar so they are insoluble in water unless they are polar.
Which of the following are categories of hydrocarbons? Select the correct answer below: a. Aromatic compounds b. Alkenes c. Alkynes d. Alkanes e. All of the above
e. All of the above. Explanation: Hydrocarbons are organic compounds with only hydrogen and carbon. They can be further classified by the kinds of bonds formed:Alkanes are hydrocarbons that contain only single bonds.Alkenes contain at least one double bond between two carbon atoms.Alkynes contain at least one triple bond between two carbon atoms.Aromatic hydrocarbons have a special pattern of alternating single and double bonds between carbons.
