Chemistry Wrong questions
Identify the conjugate acid-base pair in the following reaction: HPO32- + HSO4- ⇌ SO42- + H2PO3- A. Acid: HPO32-; conjugate base: HSO4- B. Acid: H2PO3-; conjugate base: HSO4- C. Acid: HPO32-; conjugate base: H2PO3- D. Acid: HSO4-; conjugate base: H2PO3- E. Acid: H2PO3-; conjugate base: HPO32-
A Bronsted-Lowry acid is a substance that donates an H+ and a Bronsted-Lowry base is a substance that accepts an H+. HPO32- + HSO4- ⇌ SO42- + H2PO3- In the reaction HSO4- donates an H+ to HPO32-. HSO4- is converted into SO42- and HPO32- is converted to H2PO3-. On the reactant side, HSO4- is the acid and HPO32- is the base. On the product side, H2PO3- is the acid and SO42- is the base. An acid and a base that only differ by one H+ are a conjugate acid-base pair. HSO4- and SO42- are a conjugate acid-base pair, and H2PO3- and HPO32- are a conjugate acid-base pair.
Which of the following pieces of equipment would provide the most accurate volume measurement? A. Erlenmeyer flask B. Buret C. Beaker D. Test tube E. Volumetric pipette
A pipet is used for the measurement and transfer of very precise amounts of liquid. A volumetric pipette is the most accurate piece of equipment to measure volume.
Two ideal gases, X and Y, are at the same temperature and have the same number of molecules. The pressure of gas X is twice that of gas Y. The volume of gas X will be A. twice that of gas Y. B. the same as that of gas Y. C. one-half that of gas Y. D. four times that of gas Y. E. one-fourth that of gas Y.
According to Boyle's Law, when all other properties are kept constant (temperature and number of molecules), the pressure of an ideal gas is inversely proportional to its volume. Pressure/= / 1/Volume Mathematically, Boyle's Law in this scenario can be visualized as: PxVx+PyVy Since the two properties are inversely proportional, in order for X to have a pressure twice that of Y, its volume must be one-half that of Y. 2Px*1/2Vx=PyVy
A solution of Mg(OH)2 in water becomes saturated. The addition of a strong acid to this solution will cause which of the following? Mg(OH)2(s) ⇌ Mg2+(aq) + 2OH-(aq) A. Increase the number of OH- ions in the solution B. Increase the number of Mg2+ ions in solution C. Increase the pH D. Cause MgOH2 to precipitate E. Decrease the temperature of the solution
B Mg(OH)2 is technically insoluble; however, this does not mean that none of the reactant will dissolve. A very small portion of the Mg(OH)2 will dissolve according to the following reaction: Mg(OH)2(s) ⇌ Mg2+(aq) + 2OH-(aq) The solution is saturated, meaning all the Mg(OH)2 that can dissolve has dissolved. If a strong acid is added, it will combine with the OH- to form H2O. HA(aq) + OH-(aq) ⇌ H2O(l) + A-(aq) Because some of the OH- has been removed, then according to Le Chatelier's principle, the reaction will shift to the right to restore equilibrium. As a result, more Mg(OH)2 will be dissolved, and more Mg2+ will be released in the solution.
Describe the reaction below: PCl3(g) + Cl2(g)→ PCl5(g) ; ΔHf = -87.9 kJ/mol A. Spontaneous at all temperatures B. Nonspontaneous at all temperatures C. ΔGrxn < 0 only at low temperatures D. Spontaneous only at high temperatures E. ΔGrxn < 0 only at high temperatures
C. DAT pro-tip: On the DAT, numbers can be intimidating, but if the answer choices have no numbers in them, we should think conceptually instead of empirically. Gibbs equation helps determine if a reaction is spontaneous or non-spontaneous: ΔG = ΔH - TΔS Let's estimate the value of each of the variables in the Gibbs equation: The enthalpy change (ΔH) is ΔHf = -87.9 kJ/mol which represents a negative number (-). The entropy change (ΔS), is negative (-) because the product side has fewer molecules and is more ordered than the reactant side. We can now set up the Gibbs equation as: ΔG = (negative number) - (temperature × (negative number)) ΔG = (-) - (T × (-)) Temperature is measured in Kelvin and is always a positive number. We have to think conceptually about the two possibilities for temperature: (1) If this positive temperature is relatively low, the second part of the equation is a small positive number. If you add (subtracting a negative number is the same as adding) a small positive number to a negative number, it will probably still be negative (ΔG<0). (2) If the positive temperature is relatively high, the second part of the equation is a large positive number. If you add a large positive number to a negative number, it will probably be positive (ΔG>0). The reaction is spontaneous and ΔG<0 at low temperatures.
Consider the phase diagram below for a certain substance. At which point does the gas phase start becoming indistinguishable from the liquid phase? A. I B. II C. III D. IV
D.
Which of the following properties increases along with atomic number among elements of period three? A. Ionic character B. Electronegativity C. Atomic radius D. Boiling point E. Metallic character
Electronegativity can be defined as the tendency of an atom to attract electrons. The atomic number of any atom serves as a representation of the number of protons inside the nucleus of the atom. As the number of protons increases, the electronegativity of the element will also increase as the additional positively charged protons in the nucleus make a stronger pull on the negatively charged electrons. Key Takeaway: The electronegativity of an element refers to the tendency of an atom of that element to attract electrons. The electronegativity of elements increases going right and up in the periodic table.
Which of the following statements regarding entropy is true? A. The entropy of a system will increase as temperature increases B. Spontaneous reactions require an increase in entropy C. The entropy of a system will increase as pressure increases D. The entropy of a system will decrease as volume increases
Entropy is described as the measure of disorder, or randomness, in a system. As temperature increases the molecules in the reaction move faster, more chaotic, and more random, hence an increase in entropy. B. Spontaneous reactions require an increase in entropy A reaction will be spontaneous if ΔG is negative. Temperature, enthalpy, and entropy all play a role in the reaction but do not individually determine spontaneity (ΔG = ΔH - TΔS). C. The entropy of a system will increase as pressure increases Increasing the pressure exerted on a system decreases the entropy as the molecules become more compacted and the volume available to them is reduced. D. The entropy of a system will decrease as volume increases Increasing the volume of a system allows the molecules to be less compacted and move more freely. This increases the disorder of the system, thus increasing the entropy. Key Takeaway: Increasing the temperature causes the molecules in a system to move more chaotically, increasing the entropy.
The chemical equilibrium given below is for a system in a closed vessel held at a constant temperature. What value is needed to determine the equilibrium constant? Na2CO3(s) ⇌ CO2(g) + Na2O(s)
For equilibrium reactions involving gases, we can produce equilibrium expressions in terms of pressure (Kp) instead of concentration. The formula for the equilibrium constant of a reaction involving a gas is: Kp=[Pc]^c*[Pd]^d/[Pa]^a*[Pb]^b Where [PC] and [PD] represent the pressure of products at equilibrium, while the superscripts c and d represent each product's coefficient in the chemical equation. On the other hand, [PA] and [PB] represent the pressure of reactants at equilibrium, while superscripts a and b represent each reactant's coefficient in the chemical equation. We can formulate the equilibrium expression by using the formula above and plugging each value for reactants and products. It is important to note that the equilibrium constant (Kp) expression does NOT take into account solids or liquids. Kp=Pco2 Na2CO3 and Na2O are solids and are NOT included in the equilibrium expression. The pressure of the CO2 gas is the only determinant in the equilibrium constant. Key Takeaway: For equilibrium reactions that involve gases, we can produce equilibrium expressions in terms of pressure rather than concentration. Solids and liquids are NOT included in the equilibrium expression.
Which of the following best describes the bond character for hydrochloric acid?
Hydrochloric acid (HCl) may appear ionic because it is made from hydrogen and chlorine which appear on opposite sides of the periodic table. Based on the Lewis structure of HCl and general electronegativity trends, it is clear that hydrogen and chlorine sharean electron to complete each other's valence shells: Sincechlorine is much moreelectronegativethanhydrogen, it will hog the electron more than the hydrogen, creating apolar covalent bond. B. Pure covalent Only pure elements (N2, for example) are purely covalent. C. Ionic H and Cl share an electron covalently. D. Hydrophobic HCl readily dissolves in water and is not hydrophobic. E. Hydrogen bonding HCl cannot hydrogen bond. For a hydrogen bond to occur, a H must be bonded to a N, O, or F.
Which of the following compounds is most capable of hydrogen bonding? A. HCl B. O3 C. CH3F D. NaCl E. CH3NH2
Hydrogen bonding is the strongest form of intermolecular interaction for small molecules, formed between a hydrogen atom covalently bonded to N, O, or F, and a very electronegative atom (such as N, O, or F) in another molecule. Let's visualize the Lewis structures of each molecule listed to determine where hydrogen bonding will occur: A. HCl HCl cannot hydrogen bond because it does NOT contain a hydrogen atom covalently bonded to N, O, or F. Even though chlorine is about the same electronegativity as nitrogen, it is too large and the lone pairs are not as concentrated. B. O3 D. NaCl O3 and NaCl lack hydrogen atoms and therefore, they cannot undergo hydrogen bonding. C. CH3F CH3F cannot hydrogen bond because it does NOT contain a hydrogen atom covalently bonded to N, O, or F. The hydrogens here are bound to carbon, not fluorine. E. CH3NH2 CH3NH2 can undergo hydrogen bonding because it has two hydrogen atoms covalently bonded to a very electronegative nitrogen atom. This is the compound most capable of hydrogen bonding. [E] is the answer. Key Takeaway: For a molecule to be able to undergo hydrogen bonding, it must have a hydrogen atom covalently bonded to N, O, or F.
For the given reaction below, which of the following is true? 2 Al2O3 + 3 C → 4 Al + 3 CO2 A. Carbon is oxidized, aluminum oxide is reduced B. Carbon is reduced, aluminum oxide is oxidized C. Both carbon and aluminum oxide are oxidized D. Both carbon and aluminum oxide are reduced E. Neither carbon nor aluminum oxide are changing oxidation states
Let's first find the oxidation numbers for the elements in each compound: Al2O3 (2x) + (-6) = 0 2x = +6 x = +3 CO2 (x) + (-4) = 0 x = +4 Generally in a compound, O has an oxidation number of -2. We calculated the oxidation numbers of Al and C in Al2O3 and CO2 to be +3 and +4 respectively. Finally, elements in their natural state such as Al and C have an oxidation state of 0. Now let's look at our reactant and product sides and compare the oxidation number of each element present: Aluminum (Al): +3 → 0 Carbon (C): 0 → +4 Oxygen (O): -2 → -2 Aluminum goes from +3 to 0, gaining electrons, getting reduced. Carbon goes from 0 to +4, losing electrons, getting oxidized.
Which of the following best describes why H2O has slightly smaller bond angles than CH4? A. Polarity in hydrogen bonds causes dipole attraction B. Oxygen's lone pairs repel bonding pair electrons C. H2O has trigonal planar geometry D. H2O has fewer electron pairs surrounding the central atom
Methane has a tetrahedral geometry. The bond angle between the carbon atom and any pair of hydrogen atoms is 109.5°. VSEPR theory states that atoms surrounding a central atom will tend to move as far away from each other as possible. Water also has a tetrahedral geometry. In water, two of these bonding orbitals are filled by lone pairs. These lone pairs exert a stronger repulsive force than a bond would. This makes the H-O-H bond angle about 5 degrees smaller. A. Polarity in hydrogen bonds causes dipole attraction Hydrogen bonding is a type of dipole-dipole attraction between molecules. It will not have an effect on the bond angle of H2O . C. H2O has trigonal planar geometry H2O has tetrahedral geometry, not trigonal planar geometry. D. H2O has fewer electron pairs surrounding the central atom H2O and CH4 have the same number of electron pairs surrounding their respective central atoms. There are four electron pairs surrounding the central atom in H2O and there are four electron pairs surrounding the central atom in CH4. Key Takeaway: Lone pairs in a molecule exert a stronger repulsive force than bonds which reduces the bond angle between the atoms.
How many protons, neutrons, and electrons does the following ion have, respectively? A. 6 protons, 6 neutrons, 4 electrons B. 6 protons, 6 neutrons, 8 electrons C. 6 protons, 12 neutrons, 8 electrons D. 12 protons, 6 neutrons, 14 electrons E. 18 protons, 6 neutrons, 16 electrons
The atomic number is in the bottom left and tells us how many protons the element has. Note that this determines the element, if we change the atomic number, then we are changing the element as well. In our Mg example above, the atomic number is 12, which means we have 12 protons and our element is magnesium. The mass number = protons + neutrons. Therefore, if we have a mass number of 24 in our Mg example above, and an atomic number of 12, then we must have 12 neutrons. 24 mass number - 12 atomic number = 12 neutrons. Our question gives us an atom with an atomic number of 6, meaning our atom must have 6 protons. We have a mass number of 12, and an atomic number of 6 (ie, 6 protons). This means we have 6 neutrons in our atom. Lastly, a charge is given by the number in the top right of an atomic symbol. Our atomic number tells us we have 6 protons, and in a neutral atom we should have 6 electrons. However, this ion's charge is +2, meaning we've removed two electrons, therefore our electron count is 6 - 2 = 4 electrons. Tallying up the final numbers in our question, our atom has 6 protons, 6 neutrons, and 4 electrons.
Which of the following solutions has the highest freezing point? A. 1 m H2SO4 B. 1 m C6H12O6 C. 1 m NaCl D. 1 m AlCl3 E. 1 m KCl
The formula for freezing point depression is: ΔT is the temperature change, KF is the constant for the solution, m is the molality, and i is the Van't Hoff factor. The only two properties that we are given in this problem are molality (all equal to 1 m) and the van't Hoff factor which is the number of solute particles that a compound breaks down into. In this case, we can only use the van't Hoff factor to compare and determine which compound will result in the smallest temperature change: H2SO4 → (H+) + (H+) + (SO42-) → 3 C6H12O6 → (C6H12O6) → 1 NaCl → (Na+) + (Cl-) → 2 AlCl3 → (Al3+) + (Cl-) + (Cl-) + (Cl-) → 4 KCl → (K+) + (Cl-) → 2 The Van't Hoff Factor and the temperature change are directly related according to the equation above. The compound C6H12O6 has the smallest van't Hoff factor, resulting in the smallest freezing point decrease and the final highest freezing point. Key Takeaway: Freezing point depression involves a decrease in the original freezing point of a compound. When all other properties are equal, a smaller van't Hoff factor results in a smaller freezing point decrease, and a higher final freezing point.
What is the osmotic pressure in atm of a 0.50 M aqueous solution of NaCl at 27 °C?
The formula for osmotic pressure is: π= iMRT π is the osmotic pressure, i is the van't Hoff factor, M is the molarity, R is a constant, and T is temperature. Let's assign values to each of the variables present in the osmotic pressure formula: NaCl breaks into two ions (Na+ and Cl-) in solution making the van't Hoff factor (i) = 2. The molarity (M) of the solution is given to be = 0.50 M The ideal gas constant (R) has a value of 0.082 in the osmotic pressure formula. The temperature (T) must be in degrees Kelvin: 27C + 273 = 300K. Finally, let's input these values into the osmotic pressure formula and solve the problem:
Given the following standard reduction potentials: Cu2+(aq) + 2e- → Cu(s) E°red = +0.34 V Zn2+(aq) + 2e- → Zn(s) E°red = -0.60 V What is the E°cell for the following reaction? Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) A. - 0.94 V B. - 0.26 V C. + 0.26 V D. +0.94 V
The given E°red is the standard reduction potentials for the two half-reactions that make up our full chemical equation. The half-reaction with the more positive E°red will be reduced (stronger oxidizing agent) in the full chemical equation. The half-reaction with the less positive E°red will be oxidized (stronger reducing agent). Therefore, looking at the two half-reactions we see that Cu2+ will be reduced and Zn metal will be oxidized. To find the voltage produced by an electrochemical cell, we simply find the sum of the potentials in the circuit: E°cell = E°red + E°ox. We can find E°ox by simply reversing the reduction half-reaction of Zn so that it reads: Zn(s) → Zn2+(aq) + 2e- When we reverse a half-reaction, we change the sign of its E°; thus the E°red = -0.60 V becomes E°ox = +0.60 V. Plugging this into our equation for E°cell gives the following: E°cell = 0.34 V + 0.60 V = 0.94 V
If the conjugate base of molecule X has a pKb of 1.4, what would you expect molecule X to be?
The pKb of the conjugate base of X is given to be 1.4. A lower pKb correlates to a stronger base, and a higher pKb correlates to a weaker base, which is the opposite of the pH scale. Since the conjugate base of X has a low pKb, it is strongly basic. Weak acids have a strong conjugate base. Weak bases have a strong conjugate acid. Since the conjugate base of X is strong, X must be a weak acid. DAT Pro-tip: It's important to make sure you completely understand the terms of conjugate base, conjugate acid, pKb, pKa, and how they all relate. It's easy to mix up the meanings of these definitions, and they are high-yield on the DAT. Key Takeaway: Weak acids have a strong conjugate base, while weak bases have a strong conjugate acid. Strong bases have very low pKb values, while weak bases have high pKb values.
A sample of a compound contains 7 g of nitrogen and 16 g of oxygen. What is the compound's empirical formula? A. N2O2 B. N0.5O C. N2O D. NO2
The purpose of the empirical formula is to determine the proportions of the elements present in a compound. To determine this, we must first calculate the number of moles of each element in the sample: 7 g of nitrogen = 0.5 moles of nitrogen 16 g of oxygen = 1 mole of oxygen Then, we input these values into the empirical formula to form the proportion: N0.5O The empirical formula cannot have decimals. We must multiply the subscripts by 2 to obtain a whole number. NO2 B. N0.5O You may have chosen this answer if you forgot to multiply by 2 to obtain a whole number. Empirical formulas cannot have decimals. Key Takeaways: The empirical formula determines the proportions of the elements in a compound. The empirical formula cannot have decimals.
Given the reaction 2A + B ➝ C and the provided reaction data, what is the rate law? A. rate = k[A]1[B]1 B. rate = k[B]1 C. rate = k[A]1 D. rate = k[A]2[B]1 E. rate = k[A]1[B]2
The rate law is an expression that can be used to mathematically visualize the speed at which a reaction takes place. The general formula for the rate law is: Rate= k*[A]^m*[B]^n In this equation: k is the rate constant. [A] is the concentration of species A at a specific trial, and m is the reaction order with respect to A. [B] is the concentration of species B at a specific trial, and n is the reaction order with respect to B. The only unknown variables in the rate law are m and n, which represent the reaction orders. Since m represents the reaction order in terms of A, we must look at trials in the table where [A] changes and [B] remains constant. Trials 1 and 3 fall within these requirements, let's use them to calculate the reaction order m: Let's repeat the same process for n, keeping in mind that it represents the reaction order in terms of B. Because of this, we must look at trials in the table where [B] changes and [A] remains constant. Trials 1 and 2 fall within these requirements, let's use them to calculate the reaction order n: Finally, let's use this information to build the rate law: Key Takeaway: To calculate the value of the reaction order, use the trials where the concentration of the corresponding species changes, while the concentration of any additional species remains constant.
All of the following constitute chemical changes EXCEPT one. Which is the EXCEPTION? A. Sulfuric acid neutralizing a solution of potassium hydroxide B. Pure iron metal rusting C. Hydrogen peroxide decomposing into water and oxygen D. Methane combusting to form a colorless flame E. Aluminum metal melting at high temperatures
There are two main types of changes that a compound can undergo: chemical and physical changes. Chemical changes involve changes to the compound's chemical formula or structure, and they will usually yield different products. Physical changes, do NOT involve a change to the compound's chemical structure, and will usually yield the same compound as a product. Melting aluminum does NOT constitute a chemical change. This process constitutes a physical change because aluminum passed from a solid physical state to a liquid physical state by melting. However, at the end of the process, we still have aluminum and no change to its chemical formula occurred: Aluminum(s) → Aluminum(l) A. Sulfuric acid neutralizing a solution of potassium hydroxide Any acid-base reaction will constitute a chemical change because there is an exchange of protons (H+) taking place which affects the chemical formula of the reactants to yield new products. We can visualize the reaction occurring as: H2SO4 + KOH → KHSO4 + H2O B. Pure iron metal rusting Rusting constitutes a reaction where iron will react with oxygen from the air to form iron oxide. Since a new product was formed, it constitutes a chemical change. 4 Fe + 3 O2 → 2 Fe2O3 C. Hydrogen peroxide decomposing into water and oxygen Hydrogen peroxide decomposing constitutes a chemical change because the chemical structure of the compound was altered to yield two new products (water and oxygen). This process can be visualized as: 2 H2O2 → 2 H2O + O2 D. Methane combusting to form a colorless flame The burning of a substance constitutes a combustion reaction, where the substance is combined with oxygen to yield carbon dioxide and water. Since a combustion reaction yields two new products, it constitutes a chemical change to methane: CH4 + 2 O2 → 2 H2O + CO2 Key Takeaway: Chemical changes involve changes to the chemical formula of the compound and will yield a different product. Physical changes do NOT involve changes to the chemical formula of the compound and will yield the same product.
The energy of a photon is directly proportional to which of the following? A. Charge B. Wavelength C. Speed of light D. Velocity E. Frequency
This is a lesser used formula, but it is fair game for the DAT! The energy of a photon is given by the formula: h= Planck's constant, which is 6.63 x 10-34 J・s f= photon's frequency c= speed of light, which is 3.0 x 108 m/s λ = photon's wavelength Looking at the equation, energy and frequency are directly proportional. If energy increases, frequency increases. Conversely, energy and wavelength are inversely proportional. If energy increases, wavelength decreases. This is best summarized in the following illustration. Key Takeaway: The energy of a photon is directly proportional to its frequency. The higher the energy, the higher the frequency.
25 mL of an unknown diprotic acid was titrated with 0.5 M NaOH. If 50 mL of NaOH were required to reach the equivalence point of the titration, what is the concentration of the unknown acid?
This is a titration problem between NaOH and a diprotic acid. Because we are working with a diprotic acid and a monoprotic base, we need to consider the normalities of the acid and base in our calculations. For this reason, we use the formula: n1M1V1=n2M2V2 Where n represents the number of mols of H+ or OH- the acid or base gives off. This accounts for the fact that while one mole of NaOH gives off 1 mole of OH-, every 1 mole of our diprotic acid produces 2 moles of H+. Therefore our values from the question are: n1 = 1 (only one mole of OH- from NaOH) M1 = 0.5M NaOH V1 = 50 mL and: n2 = 2 (two moles of H+ from our diprotic acid) M2 = x V2 = 25 mL Now we plug in and solve for the molarity of the unknown acid, or M2:
A closed chamber of gas at a constant temperature undergoes the following reaction at 20,000 kPa: 2H2(g) + O2(g) → 2H2O(g) Assuming 2 mols of hydrogen gas, and 1 mol of oxygen gas, what is the approximate resulting pressure (kPa) after the reaction occurs?
Use the combined gas law to solve. P1 *V1/n1*T1 = P2*V2/n2*T2 The temperature must be in Kelvin for the combined gas law. The temperature stays constant, so that variable may be ignored. This reaction occurs in a closed chamber, so volume is also constant and may be ignored. Pressure and moles are the variables that change. Looking at the balanced equation, we see there are 3 mols of gas in the reactants (n1 = 3), and 2 mols of gas in the products (n2 = 2), with a starting pressure of 20,000 kPa (P1 = 20,000). Let's input these values into the combined gas law and solve for P2:
Which one of the following will fully dissociate in water? A. HF B. CH3COOH C. H3PO4 D. HNO3 E. HSO4-
When something completely dissociates in water it means the compound, when added to water, will completely break apart into its constituent ions. By definition, a strong acid is an acid that will completely ionize in water, while weak acids only partially ionize in water. The following is a list of strong acids and bases that students should memorize for the DAT: HNO3 is the only strong acid listed and will fully dissociate when added to water. Mnemonic: Seven strong acids: So I Brought No Clean Clothes. So for sulfuric acid H2SO4. I for HI. Brought for HBr. No for nitric acid HNO3. Clean for HCl. Clothes for chloric, and perchloric acid, HClO3, HClO4.
How many grams of HCl (36 g/mol) are needed to react with Pb(OH)2 (241 g/mol) in order to produce 100g of PbCl2 (278 g/mol)? Pb(OH)2 + 2 HCl → 2 H2O + PbCl2
Write out the balanced equation: Pb(OH)2 + 2 HCl → 2 H2O + PbCl2 Use dimensional analysis to convert from g of PbCl2 to mol of HCl:
If 65 grams of sodium azide (NaN3, 65 g/mol) decomposes to form sodium and nitrogen gas, how many moles of nitrogen gas are formed? A. 0.1 mol B. 1 mol C. 1.5 mol D. 3 mol E. 5 mol
Write the balanced chemical equation: Let's use the mole ratios from the balanced equation to solve from grams of NaN3 to moles of N2: 1.5 mol of N2 is produced.