Chemistry Semester I Review
Review for first semester Chemistry course
Questions and Answers
- 1.
The density of a substance is 48 g/ml. What is the volume of a sample that is 19.2 g?
- A.
2.5 ml
- B.
0.4 ml
- C.
2.5 L
- D.
0.4 L
Correct Answer
B. 0.4 mlExplanation
The density of a substance is defined as the mass of the substance per unit volume. In this case, the density is given as 48 g/ml. To find the volume of a sample that is 19.2 g, we can use the formula: volume = mass/density. Plugging in the values, we get volume = 19.2 g / 48 g/ml = 0.4 ml. Therefore, the volume of the sample is 0.4 ml.Rate this question:
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- 2.
Express the following in scientific notation : 0.0120325 km
- A.
1.20325 x 10 +2 km
- B.
0.120325 x 10 -1 km
- C.
0.120325 x10 +1 km
- D.
1.20325 x 10 -2 km
Correct Answer
D. 1.20325 x 10 -2 kmExplanation
The given number, 0.0120325 km, can be expressed in scientific notation as 1.20325 x 10 -2 km. In scientific notation, the number is written as a decimal between 1 and 10 (1.20325) multiplied by a power of 10 (-2 in this case). This representation is used to express very large or very small numbers in a concise and standardized form.Rate this question:
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- 3.
A car is travelling at 118 km/hr. What is its speed in Mm/hr?
- A.
11.8 Mm/hr
- B.
1.18Mm/hr
- C.
0.118 Mm/hr
- D.
0.0118 Mm/hr
Correct Answer
C. 0.118 Mm/hrExplanation
The correct answer is 0.118 Mm/hr. To convert km/hr to Mm/hr, we need to divide the value by 1,000,000. Therefore, 118 km/hr divided by 1,000,000 equals 0.118 Mm/hr.Rate this question:
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- 4.
Convert 584 Us to s
Correct Answer
5.84 x 10 -4 sExplanation
The given answer, 5.84 x 10 -4 s, is the correct conversion of 584 Us to s. It represents 5.84 multiplied by 10 raised to the power of -4, which is equivalent to 0.000584. Therefore, 584 Us is equal to 0.000584 seconds.Rate this question:
- 5.
Three measurements of 34.5m, 38.4m, and 35.3m are taken. If the accepted value of the measurement is 36.7m, what is the percent error for each measurement?
- A.
5.99%, 4.63%, 3.81%
- B.
5.09%, 4.06%, 3.08%
- C.
5.55%, 4%, 3%
Correct Answer
A. 5.99%, 4.63%, 3.81%Explanation
The percent error for each measurement is calculated by subtracting the accepted value from each measurement, dividing the result by the accepted value, and then multiplying by 100 to get the percentage. For the first measurement, the percent error is (34.5 - 36.7)/36.7 * 100 = -5.99%. For the second measurement, the percent error is (38.4 - 36.7)/36.7 * 100 = 4.63%. For the third measurement, the percent error is (35.3 - 36.7)/36.7 * 100 = 3.81%. Therefore, the correct answer is 5.99%, 4.63%, 3.81%.Rate this question:
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- 6.
Determine the number of sig figs : 4080 kg
- A.
1
- B.
2
- C.
3
- D.
4
Correct Answer
C. 3Explanation
The number 4080 kg has three significant figures. The zeros between the non-zero digits are significant, indicating that they are measured or known with certainty.Rate this question:
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- 7.
Determine the number of sig figs : 0.0000481 g
- A.
8
- B.
7
- C.
3
- D.
5
Correct Answer
C. 3Explanation
The number of significant figures in 0.0000481 g is 3. The zeros before the first non-zero digit are not significant, so they are not counted. The digits 4, 8, and 1 are all non-zero and therefore significant.Rate this question:
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- 8.
Write the following in three sig figs: 0.0030850 km
- A.
0.00308 km
- B.
0.00309 km
- C.
309 km
- D.
308 km
Correct Answer
B. 0.00309 kmExplanation
The given number, 0.0030850 km, has six significant figures. When rounding to three significant figures, we look at the fourth digit, which is 5. Since it is greater than 5, we round up the third significant figure, which is 3, to 4. Therefore, the correct answer is 0.00309 km.Rate this question:
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- 9.
Write the following in three sig figs : 34.654 mg
- A.
35.7 mg
- B.
35.1 mg
- C.
34.6 mg
- D.
34.7 mg
Correct Answer
D. 34.7 mgExplanation
The given number, 34.654 mg, has four significant figures. In three significant figures, the digit after the third significant figure is 5, which is greater than or equal to 5. Therefore, we round up the third significant figure, which is 4, to 7. Hence, the correct answer is 34.7 mg.Rate this question:
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- 10.
When 5.0 g of tin reacts with hydrochloric acid, the mass of the products, tin chloride and hydrogen, totals 8.1 g. How many grams of HCl were used?
- A.
3.1 g
- B.
13.1 g
- C.
2.5 g
- D.
4.05 g
Correct Answer
A. 3.1 gExplanation
The total mass of the products (tin chloride and hydrogen) is 8.1 g. Since the initial mass of tin is 5.0 g, the mass of hydrogen can be calculated by subtracting the mass of tin chloride from the total mass of the products. Therefore, the mass of hydrogen is 8.1 g - 5.0 g = 3.1 g. Since hydrochloric acid is the source of hydrogen in this reaction, the mass of HCl used is equal to the mass of hydrogen produced, which is 3.1 g.Rate this question:
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- 11.
A compound is analyzed and found to be 50% sulfur and 50 % oxygen. If the total amount of the sulfur oxide compound is 12.5 g, how many grams of sulfur are there?
- A.
4.2 g
- B.
5.0 g
- C.
6.25 g
- D.
12.5 g
Correct Answer
C. 6.25 gExplanation
The compound is composed of equal parts of sulfur and oxygen, and the total amount of the compound is 12.5 g. Since the compound is 50% sulfur, we can calculate the amount of sulfur by multiplying the total amount of the compound by the percentage of sulfur: 12.5 g * 0.5 = 6.25 g. Therefore, there are 6.25 g of sulfur in the compound.Rate this question:
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- 12.
Two unknown compounds are analyzed. Compound I contains 5.63 g of tin and 3.37 g of chlorine, while compound II contains 2.5 g of tin and 2.98 of chlorine. Are the compounds the same?
- A.
Yes
- B.
No
Correct Answer
B. NoExplanation
The compounds are not the same because the ratio of tin to chlorine is different in each compound. Compound I has a tin to chlorine ratio of 5.63 g/3.37 g, which simplifies to 1.67 g/g. Compound II has a tin to chlorine ratio of 2.5 g/2.98 g, which simplifies to 0.84 g/g. Since the ratios are different, the compounds are not the same.Rate this question:
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- 13.
How many protons and electrons in Gallium?
- A.
39 and 31
- B.
31 and 31
- C.
31 and 39
- D.
69 and 31
Correct Answer
B. 31 and 31Explanation
Gallium has an atomic number of 31, which means it has 31 protons in its nucleus. In a neutral atom, the number of protons is equal to the number of electrons. Therefore, Gallium also has 31 electrons.Rate this question:
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- 14.
What is the atom with 37 electrons?
- A.
Ag
- B.
N
- C.
W
- D.
Rb
Correct Answer
D. RbExplanation
Rb is the correct answer because it is the chemical symbol for the element rubidium, which has an atomic number of 37. The atomic number represents the number of protons in an atom, so an atom with 37 electrons would have 37 protons as well. Therefore, the correct atom with 37 electrons is rubidium (Rb).Rate this question:
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- 15.
An isotope of copper contains 29 electrons, 29 protons and 36 neutrons. What is the mass number of this isotope?
- A.
94
- B.
65
- C.
58
- D.
29
Correct Answer
B. 65Explanation
The mass number of an isotope is the sum of its protons and neutrons. In this case, the isotope of copper has 29 protons and 36 neutrons, so the mass number is 29 + 36 = 65.Rate this question:
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- 16.
An element has two naturally occuring isotopes X-14 and X-15. X-14 has a mass of 14.00307 amu and a relative abundance of 99.63%. X-15 has a mass of 15.00011 amu and a relative abundance of 0.37%. Identify the unknown element.
- A.
O
- B.
P
- C.
N
- D.
Tc
Correct Answer
C. NExplanation
Based on the given information, the unknown element has two naturally occurring isotopes, X-14 and X-15. The mass of X-14 is 14.00307 amu and it has a relative abundance of 99.63%. The mass of X-15 is 15.00011 amu and it has a relative abundance of 0.37%. By comparing the masses and relative abundances, it can be concluded that the unknown element is Nitrogen (N).Rate this question:
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- 17.
What is the frequency of an electromagnetic wave that has a wavelength of 4.55 x 10 -3m?
- A.
1.37 x 10 +6 Hz
- B.
3.00 x 10 +8 Hz
- C.
1.52 x 10 -11 Hz
- D.
6.59 x 10 +10 Hz
Correct Answer
D. 6.59 x 10 +10 HzExplanation
The frequency of an electromagnetic wave is inversely proportional to its wavelength. As the wavelength decreases, the frequency increases. In this case, the given wavelength is 4.55 x 10^-3m, which is a very small value. Therefore, the frequency must be very high to compensate for the small wavelength. The answer 6.59 x 10^10 Hz represents a high frequency, indicating that it is the correct answer.Rate this question:
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- 18.
What is the energy of a quantum of visible light having a frequency of 5.0 x 10 +14 Hz?
- A.
3.3 x 10 -19 J
- B.
1.67 x 10 +6 J
- C.
1.5 x 10 +14 J
- D.
4.99 x 10 +14 J
Correct Answer
A. 3.3 x 10 -19 JExplanation
The energy of a quantum of visible light can be calculated using the equation E = hf, where E is the energy, h is Planck's constant (6.626 x 10^-34 J·s), and f is the frequency of the light. Plugging in the given frequency of 5.0 x 10^14 Hz into the equation, we get E = (6.626 x 10^-34 J·s)(5.0 x 10^14 Hz) = 3.3 x 10^-19 J. Therefore, the correct answer is 3.3 x 10^-19 J.Rate this question:
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- 19.
An X-ray has a frequency 1.28 x 10 +18 Hz. What is the energy of a quantum of the X-ray?
- A.
6.626 x 10 -34 Js
- B.
2.34 x 10 -10 J
- C.
8.48 x 10 -16 J
- D.
2.83 x 10 -24 J
Correct Answer
C. 8.48 x 10 -16 JExplanation
The energy of a quantum of X-ray can be calculated using the equation E = hf, where E is the energy, h is the Planck's constant, and f is the frequency. Given that the frequency of the X-ray is 1.28 x 10^18 Hz, we can substitute the values into the equation to find the energy. The correct answer of 8.48 x 10^-16 J is obtained by multiplying the frequency by the Planck's constant (6.626 x 10^-34 Js).Rate this question:
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- 20.
Write the ground state electron configuration for Cs in correct order.
- A.
1s2, 2s2, 2p6, 3s2, 3p6,3d10, 4s2, 4p6, 4d10, 5s2, 5p6, 6s1
- B.
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s1
- C.
[Rn} 6s1
- D.
{Xe} 6s2
Correct Answer
B. 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s1Explanation
The correct answer is 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s1. This electron configuration follows the Aufbau principle, which states that electrons fill the lowest energy levels first. The numbers and letters represent the different energy levels and sublevels, with the number indicating the energy level and the letter indicating the sublevel (s, p, d). The superscript numbers indicate the number of electrons in each sublevel. In this case, Cs (Cesium) has 55 electrons, so the electron configuration fills up to the 6s sublevel with 1 electron.Rate this question:
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- 21.
Which element in period 4 has 4 electrons in its electron dot structure?
- A.
Ga
- B.
Ti
- C.
Pm
- D.
Ge
Correct Answer
D. GeExplanation
Ge is the correct answer because it is the element in period 4 that has 4 electrons in its electron dot structure. The electron dot structure of an element represents the number of valence electrons it has, which are the electrons in the outermost energy level. Ge, which is Germanium, has 4 valence electrons, and therefore its electron dot structure will have 4 dots surrounding the element symbol.Rate this question:
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- 22.
What is the trend for electronegativity as you go across a period and down a group?
- A.
Increase, increase
- B.
Increase decrease
- C.
Decrease, increase
- D.
Decrease, decrease
Correct Answer
B. Increase decreaseExplanation
As you go across a period, the trend for electronegativity is to increase. This is because the number of protons in the nucleus increases, leading to a stronger pull on the electrons in the outermost energy level. On the other hand, as you go down a group, the trend for electronegativity is to decrease. This is because the atomic size increases, resulting in a greater distance between the nucleus and the outermost electrons, reducing the attractive force.Rate this question:
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- 23.
What are the names of the groups of elements in Gr18, 1, 17 and 2respectively?
- A.
Alakine metals, alkaline earth metals, halogens and noble gases
- B.
Noble gases, halogens, alkaline metals and alkaline earth metals
- C.
Noble gases, alkaline metals, halogens and alkaline earth metals
- D.
Halogens, noble gases, alkaline earth metals and alkaline metals
Correct Answer
C. Noble gases, alkaline metals, halogens and alkaline earth metalsExplanation
The correct answer is Noble gases, alkaline metals, halogens and alkaline earth metals. This answer correctly identifies the groups of elements in Gr18, 1, 17 and 2 respectively. Gr18 refers to the noble gases, which are chemically unreactive and located in the far right column of the periodic table. Group 1 consists of the alkaline metals, which are highly reactive and located in the far left column. Group 17 contains the halogens, which are also highly reactive and located in the second-to-last column. Lastly, Group 2 consists of the alkaline earth metals, which are less reactive than the alkaline metals and located to the right of Group 1.Rate this question:
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- 24.
What is the chemical formulas for magnesium sulfide?
- A.
Mg2S2
- B.
2Mg2S
- C.
MgSO4
- D.
MgS
Correct Answer
D. MgSExplanation
The correct answer is MgS. Magnesium sulfide is formed by the combination of one magnesium atom (Mg) and one sulfur atom (S), resulting in the chemical formula MgS. The other options, Mg2S2 and 2Mg2S, are incorrect because they indicate a higher number of atoms than what is actually present in the compound. MgSO4 is the chemical formula for magnesium sulfate, which is a different compound altogether.Rate this question:
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- 25.
What is the formula for iron (III) oxide?
- A.
Fe2O3
- B.
Fe3O2
- C.
3FeO
- D.
FeO3
Correct Answer
A. Fe2O3Explanation
The formula for iron (III) oxide is Fe2O3. This is because iron (III) indicates that iron has a +3 charge, while oxide has a -2 charge. In order to balance the charges, two iron atoms with a +3 charge are needed to combine with three oxygen atoms with a -2 charge, resulting in the formula Fe2O3.Rate this question:
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- 26.
What is the formula for sulfur trioxide?
- A.
S3O
- B.
SO3
- C.
S3O3
- D.
S2O3
Correct Answer
B. SO3Explanation
Sulfur trioxide is a chemical compound that consists of one sulfur atom and three oxygen atoms. The correct formula for sulfur trioxide is SO3, as it accurately represents the composition and ratio of the elements in the compound.Rate this question:
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- 27.
What is the name for K2CO3?
- A.
Dipotassium carbide
- B.
Potassium carbide
- C.
Potassium carbonate
- D.
Dipotassium carbonate
Correct Answer
C. Potassium carbonateExplanation
The correct answer is potassium carbonate. K2CO3 is the chemical formula for potassium carbonate, which is a white crystalline salt commonly used in the production of glass, soap, and fertilizers. It is composed of two potassium ions (K+) and one carbonate ion (CO3^2-).Rate this question:
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- 28.
What is the name for AuCl2?
- A.
Silver (II) chloride
- B.
Gold (I) Chloride
- C.
Gold (II) chloride
- D.
Silver (II) chloride
Correct Answer
C. Gold (II) chlorideExplanation
The correct answer is gold (II) chloride. The name "gold (II) chloride" indicates that the compound contains gold in its +2 oxidation state. The Roman numeral II represents the charge on the gold ion, while "chloride" indicates that the compound is composed of chloride ions. This naming convention is used to specify the oxidation state of the metal in the compound.Rate this question:
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- 29.
What is the name for N2O5?
- A.
Nitorgen oxide
- B.
Nitrogen pentoxide
- C.
Dinitrogen oxide
- D.
Dinitrogen pentoxide
Correct Answer
D. Dinitrogen pentoxideExplanation
Dinitrogen pentoxide is the correct name for N2O5. The prefix "di-" indicates that there are two nitrogen atoms in the compound, and the prefix "pent-" indicates that there are five oxygen atoms. Therefore, the name "dinitrogen pentoxide" accurately describes the composition of N2O5.Rate this question:
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- 30.
What is the name for HBr?
- A.
Hydrogen bromine
- B.
Hyrdrobromic acid
- C.
Hydrogen monobromide
- D.
Hydrogen bromide acid
Correct Answer
B. Hyrdrobromic acidExplanation
Hydrobromic acid is the correct name for HBr. It is formed by the combination of hydrogen (H) and bromine (Br) atoms. The term "acid" indicates that it is an aqueous solution of HBr, where the compound dissociates into H+ and Br- ions. The name "hydrobromic" follows the naming convention for binary acids, where the prefix "hydro-" is added to the name of the nonmetal (bromine) and the suffix "-ic" is used. Therefore, hydrobromic acid accurately describes the compound HBr.Rate this question:
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- 31.
What is the formula for Carbonic acid?
- A.
H2CO3
- B.
H4C
- C.
HCO
- D.
H2CO
Correct Answer
A. H2CO3Explanation
Carbonic acid is a chemical compound that can be represented by the formula H2CO3. This formula indicates that carbonic acid consists of two hydrogen atoms (H2), one carbon atom (C), and three oxygen atoms (O3). The subscript numbers in the formula indicate the number of atoms of each element present in the compound. Therefore, H2CO3 is the correct formula for carbonic acid.Rate this question:
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- 32.
How many resonance structures are present in the CO3 (-2) ion are there?
- A.
1
- B.
2
- C.
3
- D.
0
Correct Answer
C. 3Explanation
The CO3 (-2) ion, also known as the carbonate ion, consists of three oxygen atoms bonded to a central carbon atom. In order to determine the number of resonance structures, we need to examine the possible arrangements of double bonds within the molecule. By moving the double bonds around, we can create three different resonance structures for the CO3 (-2) ion. Therefore, the correct answer is 3.Rate this question:
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- 33.
What is the geometric shape and polarity for OCl2?
- A.
Linear, nonpolar
- B.
Bent, nonpolar
- C.
Bent, polar
- D.
Linear, polar
Correct Answer
C. Bent, polarExplanation
OCl2 has a bent shape because it has two bonding pairs and two lone pairs of electrons around the central oxygen atom. The presence of lone pairs causes the molecule to have a bent shape. OCl2 is polar because the oxygen atom is more electronegative than the chlorine atoms, resulting in an uneven distribution of charge. The oxygen atom pulls the electron density towards itself, creating a partial negative charge on the oxygen atom and partial positive charges on the chlorine atoms.Rate this question:
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- 34.
What is the shape and polarity for CH2O?
- A.
Trigonal planar, nonpolar
- B.
Trigonal pyrimidal, nonpolar
- C.
Trigonal planar, polar
- D.
Trigonal pyrimidal, polar
Correct Answer
C. Trigonal planar, polarExplanation
The correct answer is trigonal planar, polar. CH2O, also known as formaldehyde, consists of a central carbon atom bonded to two hydrogen atoms and one oxygen atom. The molecule has a trigonal planar shape, with the oxygen atom at the center and the hydrogen and carbon atoms forming a flat triangular arrangement around it. The molecule is polar because the oxygen atom is more electronegative than the carbon and hydrogen atoms, creating a partial negative charge on the oxygen atom and partial positive charges on the hydrogen and carbon atoms.Rate this question:
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