1. Two samples of solids have similar reactivity with acids and similar densities. Their masses and volumes, however, are not at all similar. Is it possible that these are the same substance?
-Yes, it is possible because they have similar intensive properties.
2. Melting gold with other metals makes 10-karat gold. Which term best describes 10-karat gold?
-homogeneous mixture
3. How do chemists predict the shapes of molecules?
-Due to the repulsion between electrons, valence electrons will be arranged as far apart from each other as possible.
4. Lead has an atomic number of 82. Which statement describes all neutral atoms and ions of lead?
-Neutral atoms of lead must have 82 protons. Ions must have 82 protons, as well.
5. How did the study of the atom contribute to our understanding of the periodic table of the elements?
-Experiments that identified characteristics of atoms provided scientists with atomic weights and atomic numbers, which were used to organize the periodic table.
6. Hydrogen is in Group 1 of the periodic table. Which kind of bond would form between two hydrogens?
-A covalent bond would form because the electron would be shared so both hydrogens have a full, stable shell.
7. Which of the following elements are most likely to form an ionic bond?
-K and Cl
8. Which example accurately describes a solution?
-Polar sugar molecules dissolve in water, which is polar.
9. How do temperature changes lead to solubility changes for salt dissolved in water?
-High temperatures mean more kinetic energy, which keeps sodium and chlorine ions from combining, which increases solubility.
10. Which statement best describes a weak base?
-It accepts protons and only partially dissociates in water.
11. Use the periodic table to answer the question. Which comparison is correct?
-PH3 is a stronger acid than NH3.
12. In an experiment involving a balloon, a scientist notices that the gas particles within the balloon begin to move faster, resulting in the balloon expanding. Which statement best describes the experiment?
-The scientist is investigating Charles’s law, which shows that temperature and volume are directly proportional.
13. Use the periodic table to answer the question.How is an atom of the element xenon (Xe) likely to act during a chemical reaction?
-It will likely be unreactive.
14. Under certain conditions, water can be separated into oxygen and hydrogen gases according to the equation 2H2O → 2H2 + O2.
In a lab, 112g of hydrogen gas and 888g of oxygen gas were collected. Student A says that the amount of water to start cannot be determined, but Student B says that the water must have been 1000g. Who is correct?
-Student B, because of the law of conservation of matter.
15. Molecules that are made up of two of the same atom have nonpolar covalent bonds. Which statement best explains this property?
-The atoms have the same electronegativity.
16. Lithium (Li) bonds with another atom to form a stable molecule with formula LiX. Based on groups in the periodic table, which atom could represent X?
-bromine (Br)
17. Will the following replacement reaction occur?
MgCl2 + I2 → ?
-No, it will not because iodine is less reactive than chlorine.
18. During photosynthesis, water (H2O) and carbon dioxide (CO2) are combined to make glucose (C6H12O6) and oxygen (O2). Which equation is balanced?
-6H2O + 6CO2 → C6H12O6 + 6O2
19. Which charge does iron (Fe) have in iron sulfate (FeSO4)?
- +2
20.It takes 60 mL of 0.20 M of sodium hydroxide (NaOH) to neutralize 25 mL of carbonic acid (H2CO3) for the following chemical reaction:
2 NaOH + H2CO3 → Na2CO3 + 2 H2O
The concentration of the carbonic acid is _____.
- 0.24 M
21. An unknown substance has a boiling point of 174°C. Which statement is true about this unknown substance?
-It has a higher boiling point than water, and it likely has stronger electrostatic forces between its molecules than water.
22. Use the table to answer the question.
Substance Melting Point (ºC)
castor oil –9.8
phenol 43.2
benzene 5.7
formic acid 8
Which substance has the weakest bonds between its molecules?
-castor oil
23. Two substances both exhibit hydrogen bonding. Substance A has a boiling point of 78.4ºC. Substance B has a boiling point of 100ºC. Which statement correctly compares the substances?
-Substance B has stronger bonds, and it takes more energy to undergo a phase change.
24. A student performs an experiment to determine the melting point of ice in order to investigate the strength of electrostatic forces between its molecules. Once the student completes the experiment, which additional action should the student take?
-The student should perform multiple trials of the same experiment, then take the average of all of the results.
25. In which case would recalibrating a thermometer be an important next step in an experiment dealing with boiling points?
-The results of several trials are all very close to each other, but they are noticeably different from the accepted value for the boiling point.