Pre Test In General Chemistry
Questions and Answers
- 1.
What is the concentration, in percent by mass, of 0.62 g of solute in 45.0 g of solution?
- A.
0.014%
- B.
0.13%
- C.
1.38%
- D.
1.37%
Correct Answer
C. 1.38%Explanation
The concentration of a solution is calculated by dividing the mass of the solute by the mass of the solution and multiplying by 100. In this case, the mass of the solute is given as 0.62 g and the mass of the solution is 45.0 g. Dividing 0.62 g by 45.0 g and multiplying by 100 gives a concentration of 1.38%.Rate this question:
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- 2.
What mass of solute is needed to make 100.0 g of a 3.4% solution?
- A.
3.4 g
- B.
34g
- C.
2941g
- D.
0.34 g
Correct Answer
A. 3.4 gExplanation
To calculate the mass of solute needed to make a 3.4% solution, we need to determine what 3.4% of 100.0 g is. This can be done by multiplying 100.0 g by 0.034 (which is the decimal form of 3.4%). The result is 3.4 g, which is the mass of solute needed to make the solution.Rate this question:
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- 3.
What is the percent by volume of a solution made by dissolving 20 ml of ethyl alcohol into 180 ml of water?
- A.
10.0%
- B.
80.0%
- C.
11.1%
- D.
20.0%
Correct Answer
A. 10.0%Explanation
To find the percent by volume of the solution, we need to calculate the volume of ethyl alcohol in the solution and divide it by the total volume of the solution, then multiply by 100. In this case, 20 ml of ethyl alcohol is dissolved in 180 ml of water, giving a total volume of 200 ml. The volume of ethyl alcohol is 20 ml. Dividing 20 ml by 200 ml and multiplying by 100 gives us 10.0%. Therefore, the correct answer is 10.0%.Rate this question:
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- 4.
How many electrons are there in Helium?
- A.
1
- B.
2
- C.
3
- D.
4
Correct Answer
B. 2Explanation
Helium has 2 electrons. This is because the atomic number of helium is 2, which indicates the number of electrons in a neutral atom. Each electron carries a negative charge and orbits around the nucleus of the helium atom. Therefore, the correct answer is 2.Rate this question:
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- 5.
What is the charge of a proton?
- A.
Negative
- B.
Positive
- C.
Zero
- D.
Neutral
Correct Answer
B. PositiveExplanation
A proton is a subatomic particle found in the nucleus of an atom and it carries a positive charge. It is one of the fundamental particles that make up an atom along with neutrons and electrons. The positive charge of a proton is equal in magnitude but opposite in sign to the negative charge of an electron. This charge difference between protons and electrons is what creates the electrical interactions and chemical behavior of atoms.Rate this question:
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- 6.
Which of the following will have a larger radius than zinc?
- A.
Helium
- B.
Oxygen
- C.
Carbon
- D.
Strontium
Correct Answer
D. StrontiumExplanation
Strontium will have a larger radius than zinc because as you move down a group in the periodic table, the atomic radius generally increases. Strontium is located below zinc in the periodic table, so it will have more energy levels and a larger atomic radius.Rate this question:
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- 7.
Which of the following will have a higher electronegativity than arsenic?
- A.
Carbon
- B.
Neon
- C.
Antimony
- D.
Germanium
Correct Answer
A. CarbonExplanation
Carbon will have a higher electronegativity than arsenic because electronegativity generally increases across a period from left to right on the periodic table. Carbon is located to the left of arsenic on the periodic table, indicating that it has a higher electronegativity.Rate this question:
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- 8.
What atom matches this electron configuration? 1s22s22p63s2
- A.
Neon
- B.
Magnesium
- C.
Aluminum
- D.
Potassium
Correct Answer
B. MagnesiumExplanation
The electron configuration 1s22s22p63s2 corresponds to the element magnesium. This is because the electron configuration represents the arrangement of electrons in an atom's energy levels. In this case, the first energy level has 2 electrons (1s2), the second energy level has 2 electrons (2s2), the second energy level's p orbital has 6 electrons (2p6), and the third energy level has 2 electrons (3s2). This matches the electron configuration of magnesium, which has an atomic number of 12 and is represented by the symbol Mg.Rate this question:
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- 9.
How many valence electrons are there in 1s22s22p6
- A.
6
- B.
2
- C.
10
- D.
8
Correct Answer
D. 8Explanation
The given electron configuration represents the arrangement of electrons in an atom. The numbers in the configuration indicate the number of electrons in each energy level and orbital. In this case, the electron configuration 1s22s22p6 represents the filling of the 1s, 2s, and 2p orbitals. Adding up the electrons in each orbital gives a total of 8 valence electrons.Rate this question:
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- 10.
Which from the following is in its excited state?
- A.
1s22s22p5
- B.
1s22s22p6
- C.
1s22s12p6
- D.
1s22s22p63s1
Correct Answer
C. 1s22s12p6Explanation
The electron configuration 1s22s12p6 represents the ground state of an atom since it follows the Aufbau principle and all the orbitals are filled. In the excited state, electrons are promoted to higher energy levels. Therefore, the correct answer is 1s22s22p63s1, where the electron in the 3s orbital indicates that the atom is in an excited state.Rate this question:
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- 11.
A chemical bond is:
- A.
Made up of electrons
- B.
An attractive force that holds atoms together
- C.
Made up of protons
- D.
An attractive force that holds molecules together
Correct Answer
B. An attractive force that holds atoms togetherExplanation
A chemical bond is an attractive force that holds atoms together. It is not made up of electrons or protons, but rather it is the force that results from the interaction between electrons and nuclei. This force is responsible for the formation of molecules, as it holds the atoms together in a stable arrangement.Rate this question:
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- 12.
If an atom of nitrogen gains 3 electrons, what is its overall charge?
- A.
Neutral
- B.
+3
- C.
-3
- D.
-1
Correct Answer
C. -3Explanation
If an atom of nitrogen gains 3 electrons, it will have a negative charge. The overall charge of the atom will be -3, indicating that it has gained 3 negatively charged electrons. This means that the atom now has more electrons than protons, resulting in a net negative charge.Rate this question:
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- 13.
Elements on the left side of the periodic table will most likely form:
- A.
Positive Ions
- B.
Negative Ions
- C.
Neutral Ions
- D.
None of these
Correct Answer
A. Positive IonsExplanation
Elements on the left side of the periodic table, also known as the metals, tend to lose electrons during chemical reactions. This electron loss results in the formation of positive ions, also known as cations. Therefore, it is likely that elements on the left side of the periodic table will form positive ions.Rate this question:
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- 14.
What type of molecule is this?
- A.
Alcohol
- B.
Aldehyde
- C.
Ketone
- D.
Carboxylic Acid
Correct Answer
A. AlcoholExplanation
The given molecule is classified as an alcohol. Alcohols are organic compounds that contain a hydroxyl (-OH) functional group attached to a carbon atom. In this case, the molecule is likely to have an -OH group attached to a carbon atom, indicating that it is an alcohol. Aldehydes, ketones, and carboxylic acids have different functional groups and structures, so they are not the correct classification for this molecule.Rate this question:
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- 15.
What type of molecule is this?
- A.
Alcohol
- B.
Aldehyde
- C.
Ketone
- D.
Carboxylic Acid
Correct Answer
C. KetoneExplanation
The correct answer is ketone. A ketone is a type of organic molecule that contains a carbonyl group, which is a carbon atom double-bonded to an oxygen atom. In this molecule, there is a carbonyl group bonded to two other carbon atoms. Alcohols have a hydroxyl group (-OH), aldehydes have a carbonyl group bonded to at least one hydrogen atom, and carboxylic acids have a carboxyl group (-COOH). Therefore, none of these options accurately describe the molecule in question.Rate this question:
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- 16.
What type of molecule is this?
- A.
Alcohol
- B.
Aldehyde
- C.
Ketone
- D.
Carboxylic Acid
Correct Answer
B. AldehydeExplanation
An aldehyde is a type of molecule that contains a carbonyl group (C=O) bonded to at least one hydrogen atom. It is characterized by the presence of the functional group -CHO. In this case, the molecule is identified as an aldehyde because it has a carbonyl group bonded to a carbon atom and a hydrogen atom. It is not an alcohol because it does not have an -OH group, a ketone because it does not have two alkyl groups bonded to the carbonyl carbon, or a carboxylic acid because it does not have a -COOH group.Rate this question:
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- 17.
The equation PV = nRT shows the relationship between a variety of gas properties. What is this equation called?
- A.
Gay - Lussac's Law
- B.
Boyle's Law
- C.
Ideal Gas Law
- D.
Charles' Law
Correct Answer
C. Ideal Gas LawExplanation
The equation PV = nRT is known as the Ideal Gas Law. This equation relates the pressure (P), volume (V), number of moles (n), gas constant (R), and temperature (T) of an ideal gas. It describes the behavior of gases under various conditions and is widely used in the study of thermodynamics and gas laws.Rate this question:
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- 18.
Boyle's law relates the way two gas properties change when another property remains the same. What are the two changing properties in Boyle's Law?
- A.
Temperature and Volume
- B.
Pressure, temperature and volume
- C.
Pressure and Temperature
- D.
Pressure and Volume
Correct Answer
D. Pressure and VolumeExplanation
Boyle's law states that the pressure of a gas is inversely proportional to its volume, as long as the temperature remains constant. This means that as the pressure of a gas increases, its volume decreases, and vice versa. Therefore, the correct answer is "Pressure and Volume" because these are the two properties that change in relation to each other according to Boyle's law.Rate this question:
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- 19.
A container is originally at 5 Kelvin and 10 atm. If the temperature is raised to 10 Kelvin, what will be the new pressure of the container?
- A.
15 atm
- B.
35 atm
- C.
25 atm
- D.
20 atm
Correct Answer
D. 20 atmExplanation
When the temperature of a gas increases, its pressure also increases, assuming the volume remains constant. This relationship is described by the ideal gas law, which states that pressure is directly proportional to temperature. Therefore, when the temperature of the container is raised from 5 Kelvin to 10 Kelvin, the pressure will also increase. Since the original pressure is 10 atm, the new pressure would be 20 atm.Rate this question:
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- 20.
Which reaction indicates a synthesis reaction?
- A.
2HgO (s) ----> 2Hg (l) + O2 (g)
- B.
CH4 (g) + 2O2 (g) -----> CO2 (g) + 2H2O
- C.
Zn + Cu2+ ----> Zn2+ + Cu
- D.
4H2(g) + 2O2 (g) -----> 4H2O
Correct Answer
D. 4H2(g) + 2O2 (g) -----> 4H2OExplanation
The reaction 4H2(g) + 2O2 (g) -> 4H2O represents a synthesis reaction because it involves the combination of two or more substances to form a single product. In this case, four molecules of hydrogen (H2) and two molecules of oxygen (O2) combine to form four molecules of water (H2O). This reaction follows the general form of a synthesis reaction, where A + B -> AB.Rate this question:
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- 21.
What is the mass of 4.20 mol of the element iron (Fe)?
- A.
235g
- B.
55.8g
- C.
134g
- D.
60g
Correct Answer
A. 235gExplanation
The correct answer is 55.8g. The molar mass of iron (Fe) is 55.8g/mol. Therefore, to find the mass of 4.20 mol of iron, we can multiply the molar mass by the number of moles: 55.8g/mol * 4.20 mol = 235g.Rate this question:
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- 22.
How many moles are there in 19.82g Mg?
- A.
1.226 mol
- B.
481.7 mol
- C.
1.000mol
- D.
0.8156 mol
Correct Answer
D. 0.8156 molExplanation
To find the number of moles in a given mass of a substance, we need to divide the mass by the molar mass of the substance. The molar mass of Mg (magnesium) is 24.31 g/mol. Dividing 19.82 g by 24.31 g/mol gives us approximately 0.8156 mol. Therefore, there are 0.8156 moles in 19.82g of Mg.Rate this question:
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- 23.
What is the name of this compound (NH4)3PO4?
- A.
Ammonia phosphite
- B.
Ammonia phosphate
- C.
Ammonium phosphate
- D.
Ammonium phosphite
Correct Answer
C. Ammonium pHospHateExplanation
The compound (NH4)3PO4 is called ammonium phosphate because it consists of ammonium ions (NH4+) and phosphate ions (PO4-). The compound is formed by combining three ammonium ions with one phosphate ion, resulting in the formula (NH4)3PO4. Ammonium phosphate is commonly used as a fertilizer due to its high phosphorus content, which is essential for plant growth.Rate this question:
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- 24.
What is the chemical formula of cobalt (III) nitrite?
- A.
Cu(NO3)3
- B.
Co(NO3)3
- C.
Cu(NO2)3
- D.
Co(NO2)3
Correct Answer
D. Co(NO2)3Explanation
The correct answer is Co(NO2)3. Cobalt (III) nitrite is a compound that consists of one cobalt ion (Co3+) and three nitrite ions (NO2-). The chemical formula Co(NO2)3 represents this compound, where the cobalt ion is bonded to three nitrite ions.Rate this question:
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- 25.
Which represents a decrease in entropy?
- A.
Sublimation of CO2
- B.
Boiling water
- C.
Condensation of steam
- D.
NaCl dissolving in water
Correct Answer
C. Condensation of steamExplanation
Condensation of steam represents a decrease in entropy because it involves the conversion of a gas (steam) into a liquid (water). In the gaseous state, the particles have more freedom of movement and are more disordered, leading to higher entropy. However, during condensation, the particles come together and form a more ordered and compact liquid state, resulting in a decrease in entropy.Rate this question:
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- 26.
Consider the following reaction: 2 H2O + energy ------> 2H2 + O2
- A.
Exothermic, releasing energy
- B.
Exothermic, absorbing energy
- C.
Endothermic, absorbing energy
- D.
Endothermic, releasing energy
Correct Answer
C. Endothermic, absorbing energyExplanation
The given reaction is endothermic because it absorbs energy. In an endothermic reaction, the products have a higher energy level than the reactants, and energy is absorbed from the surroundings to drive the reaction forward. In this case, the reactants (2 H2O) absorb energy to produce the products (2H2 + O2).Rate this question:
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- 27.
How many moles of ammonium is produced when 3 moles of nitrogen reacts with hydrogen? N2 + 3H2 -----> 2NH3
- A.
2 moles
- B.
1.5 moles
- C.
9 moles
- D.
6 moles
Correct Answer
D. 6 molesExplanation
When 3 moles of nitrogen react with hydrogen, according to the balanced equation, 2 moles of ammonia (NH3) are produced. Therefore, the correct answer is 2 moles.Rate this question:
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- 28.
What is stoichiometry?
- A.
Math of Chemistry
- B.
Calculations based from balanced chemical equation
- C.
Balancing equation
- D.
Predicting the products of chemical reaction
Correct Answer
B. Calculations based from balanced chemical equationExplanation
Stoichiometry refers to the calculations and relationships between the quantities of reactants and products in a chemical reaction. It involves using a balanced chemical equation to determine the mole ratios between different substances involved in the reaction. These calculations are essential for determining the amount of reactants needed, the amount of products that will be formed, and for predicting the outcome of a chemical reaction. Stoichiometry is a fundamental concept in chemistry and is used to understand and analyze chemical reactions at a quantitative level.Rate this question:
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