Question 1

Which of the following pairs of compounds are allotropes?

Accepted Answer

Allotropy occurs when a single element exists in multiple forms. In the context of this question, only one pair of compounds consists of a single element. Thus, O₂ and O3 are an allotropes.

Question 2

What is the expected H-C-H bond angle in a molecule of CH4?

Accepted Answer

CH₄displays tetrahedral molecular geometry. Therefore, the expected H-C-H bond angle is 109.5 degrees.

Question 3

Which of the following gases is the third most abundant in the Earth's atmosphere?

Accepted Answer

The third most abundant gas in the Earth's atmosphere is argon.

Question 4

A neutral element has a mass number of 23 and 12 neutrons. What is the identity of this element?

Accepted Answer

The mass number of an element is the number of protons and neutrons in an atom of that element. Subtracting the number of neutrons present from the mass number gives the atomic number. Such a calculation indicates that the unknown in this question is sodium.

Question 5

Which of the following is the correct molecular formula for hydrobromic acid?

Accepted Answer

The nomenclature system for acids is fairly simple. The "hydro" refers to the hydrogen while the "bromic" refers to the bromine. The correct formula is HBr.

Question 6

Find the pH of the a 0.500M solution of the weak base Ammonia (NH₃). The K_b = 1.78*10^-5NH₃ +H₂O --> NH₄+ + OH^-

Accepted Answer

The solution is as follows: The equilibrium equation is K_b=[NH₄][OH^-]/[NH₃] Since NH₃ will not fully dissociate, the concentrations of OH^- and HN3 are unknown (x) and the concentration of NH3 at equilibrium will be 0.5 - x. K_b = [x][x]/[0.500-x] Assuming x is so small it's negligible, that yields; K_b = x²/[0.500] (1.78 * 10^-5) = x²/[0.500] (1.78 * 10^-5) * 0.500 = x² x= .003M which is the concentration of OH^- Using the equilibrium equation for water, we have H₂O ^® H⁺ + OH^- The equilbrium value, K_w is 10^-14 K_w = [H⁺][OH^-] * 10^-14= [H⁺][0.003] [H⁺] = 3.33*10^-12 pH = -log [H⁺] = -log (3.33 * 10^-12) = 11.48

Question 7

What property of a metal refers to its ability to be hammered into sheets?

Accepted Answer

Malleability refers to a metal's ability to be hammered into sheets.

Question 8

You are dissolving a gas in water. If the partial pressure of the gas is 1 atm, and the concentration is .5g per 50mL of solution, then what is the concentration of gas at 800mmHg? How many grams of gas are dissolved in the water now?

Accepted Answer

The solution is as follows: C = concentration (g/mL) P = pressure (atm) C1/P1 = C2/P2 C₁=.5g/50mL = .01g/mL ^® P₁=1.0 atm C₂ = ? P₂ = 1000 mmHg * 1 atm/760mmHg = 1.32atm (.01g/mL)/(1.0atm) = C2/(1.32atm) C₂= .013g/mL At V = 50mL, this means there are 0.013g/mL * 50mL = 0.66g dissolved.

Question 9

Which of the following is the correct molecular formula for magnesium phosphate?

Accepted Answer

Phosphate is a polyatomic anion with the molecular formula PO₄^3-, and magnesium typically takes an oxidation state of +2. The simplest way to balance these charges gives the correct molecular formula, Mg₃(PO₄)₂.

Question 10

Which of the following elements is most easily reduced?

Accepted Answer

Easily reduced elements readily accept electrons. The additional electrons help these elements establish stable valence configurations. In the context of this question, chlorine is the most willing to accept an additional electron, so it is the most easily reduced.

Question 11

Which of the following is false about the ionic character of bonds?

Accepted Answer

Covalent bonds can have some ionic character due to differences in electronegativity between the atoms, leading to unequal sharing of electrons. This means that covalent bonds can indeed have ionic character, making statement A false.

Question 12

You have a closed container filled with 1L of pure air at STP. Assume that this air is made of only nitrogen (79%) and oxygen (21%). What are the partial pressures of nitrogen and oxygen in the box?Hint: X_N = P_N/PTotal= N_N/N_Total

Accepted Answer

X_N=mole fraction of nitrogen N_N=moles of nitrogen N_Total=moles total X₀=mole fraction of oxygen N_o=moles of oxygen Since 79% of the air is nitrogren, the mole fraction (x_N) is .79. (X_N=N_N/NTotal). Likewise, the mole fraction for oxygen is .21. This is calculated by realizing that 79% of the air is nitrogen, therefore 79% of the molecules (or moles) are nitrogen. So, you don't need to know NN or NTotal to calculate this. Partial pressure equations are as follows: XN = P_N/P_Total= N_N/NTotal .79 = P_N/P_Total .79*P_Totall = P_N .79 * 1.0 atm = PN = .79 atm P₀= P_Total- P_N= 1.0 atm - .79 atm = .21 atm

Question 13

A fixed quantity of a gas undergoes a change in temperature from 100 K to 200 K and a change in pressure from 2 atm to 1 atm. After theses changes, the volume of the gas is

Accepted Answer

The pressure, temperature, and volume of a gas are related by the ideal gas law, PV=nRT. Solving for volume gives the equation V=(nRT/P). The molar quantity of gas (n) is constant, so the equation reduces to V=T/P. In the context of the question, temperature is doubled while pressure is halved, resulting in a four-fold increase in volume.

Question 14

Which of the following elements is the most electronegative?

Accepted Answer

This question addresses periodic trends in electronegativity. Electronegativity increases going up a group and across a period from left to right. Therefore, fluorine is the most electronegative element. In fact, fluorine is the most electronegative element in the entire periodic table.

Question 15

1)75 moles of NaCl are dissolved in 1.00 kg of water. What is the boiling point of this solution (k_b = .512 degrees C·kg/mol for water)?

Accepted Answer

This problem addresses the colligative property of boiling point elevation. Ionic solids raise the boiling point of a solution according to the formula (change in boiling point) = m x k_b x i. In this case, i takes a value of two, since two ions form from every molecule of solid NaCl. Plugging in for the variables indicates that the correct boiling point for this solution is 101.79 degrees Celsius.

Question 16

What is the order of reaction for the following equation?A + B --> 2C

Accepted Answer

r=k[A]¹[B]¹ where the "1" comes from the stoichoimetry. Only the reactants are used when determining rate. The order of a reaction is the sum (in this case 1+1). Thus, it is second order.

Question 17

Calculate the bond dissociation energy in the following equation:CH₄(g) + 2O₂(g) --> CO₂(g) + 2H₂0 (g)Given the following:DH_f° C-H = 87 Kcal/molDH_f° O=O = 118 Kcal/molDH_f° C=O = 178 Kcal/molDH_f° O-H = 111 Kcal/mol

Accepted Answer

DH_diss° = [energy of bonds broken] - [energy of bonds formed] In the equation, you have the following bonds: 4C-H (CH₄) + 2 O=O --> O=C=O + 2 H-O-H ***OR*** 4C-H + 2O=O --> 2 C=O + 4 O-H Using the heats of formation provided, the equation becomes DH_diss° = [(4*87) + (2*118)] - [(2*178) +(4*111)] = -216KCal

Question 18

Which of the following sets of quantum numbers is impossible for an electron?

Accepted Answer

The principle quantum number can take any positive integer value. The angular quantum number can take any positive integer value up to (n-1). The magnetic quantum number can take any value -l through +l. Thus, the set of quantum numbers n = 2, l = 1, ml = 2, s = -½ is impossible because the magnetic quantum number is larger than the angular quantum number.

Question 19

Which of the following hybridizations would allow for the formation of one pi bond?

Accepted Answer

Sp² hybridization allows for a single double bond to occur (flat, triangular formation). Sp³ allows for single bonds only, sp allows for triple bonds. S²is not a hybridization.

Question 20

A cell placed in pure water has swelled. Why?
A)The cell was in an isotonic environment, so water flowed into it.
B)The cell was in a hypotonic environment, so water flowed into it.
C)The cell was in a hypertonic environment, so water flowed into it.
D)The cell was in a hypotonic environment, so water flowed out of it.
E)The cell was in a hypertonic environment, so water flowed out of it.

Accepted Answer

The answer of A cell placed in pure water has...

Quiz 2: Chemistry

Which of the following pairs of compounds are allotropes?

What is the expected H-C-H bond angle in a molecule of CH4?

Which of the following gases is the third most abundant in the Earth's atmosphere?

A neutral element has a mass number of 23 and 12 neutrons. What is the identity of this element?

Which of the following is the correct molecular formula for hydrobromic acid?

Find the pH of the a 0.500M solution of the weak base Ammonia (NH₃) . The K_b = 1.78*10^-5NH₃ +H₂O --> NH₄+ + OH^-

What property of a metal refers to its ability to be hammered into sheets?

You are dissolving a gas in water. If the partial pressure of the gas is 1 atm, and the concentration is .5g per 50mL of solution, then what is the concentration of gas at 800mmHg? How many grams of gas are dissolved in the water now?

Which of the following is the correct molecular formula for magnesium phosphate?

Which of the following elements is most easily reduced?

Which of the following is false about the ionic character of bonds?

You have a closed container filled with 1L of pure air at STP. Assume that this air is made of only nitrogen (79%) and oxygen (21%) . What are the partial pressures of nitrogen and oxygen in the box?Hint: X_N = P_N/PTotal= N_N/N_Total

A fixed quantity of a gas undergoes a change in temperature from 100 K to 200 K and a change in pressure from 2 atm to 1 atm. After theses changes, the volume of the gas is

Which of the following elements is the most electronegative?

1) 75 moles of NaCl are dissolved in 1.00 kg of water. What is the boiling point of this solution (k_b = .512 degrees C·kg/mol for water) ?

What is the order of reaction for the following equation?A + B --> 2C

Calculate the bond dissociation energy in the following equation:CH₄(g) + 2O₂(g) --> CO₂(g) + 2H₂0 (g) Given the following:DH_f° C-H = 87 Kcal/molDH_f° O=O = 118 Kcal/molDH_f° C=O = 178 Kcal/molDH_f° O-H = 111 Kcal/mol

Which of the following sets of quantum numbers is impossible for an electron?

Which of the following hybridizations would allow for the formation of one pi bond?

Quiz 2: Chemistry

Which of the following pairs of compounds are allotropes?

What is the expected H-C-H bond angle in a molecule of CH4?

Which of the following gases is the third most abundant in the Earth's atmosphere?

A neutral element has a mass number of 23 and 12 neutrons. What is the identity of this element?

Which of the following is the correct molecular formula for hydrobromic acid?

Find the pH of the a 0.500M solution of the weak base Ammonia (NH3) . The Kb = 1.78*10-5NH3 +H2O --> NH4+ + OH-

What property of a metal refers to its ability to be hammered into sheets?

You are dissolving a gas in water. If the partial pressure of the gas is 1 atm, and the concentration is .5g per 50mL of solution, then what is the concentration of gas at 800mmHg? How many grams of gas are dissolved in the water now?

Which of the following is the correct molecular formula for magnesium phosphate?

Which of the following elements is most easily reduced?

Which of the following is false about the ionic character of bonds?

You have a closed container filled with 1L of pure air at STP. Assume that this air is made of only nitrogen (79%) and oxygen (21%) . What are the partial pressures of nitrogen and oxygen in the box?Hint: XN = PN/PTotal= NN/NTotal

A fixed quantity of a gas undergoes a change in temperature from 100 K to 200 K and a change in pressure from 2 atm to 1 atm. After theses changes, the volume of the gas is

Which of the following elements is the most electronegative?

1) 75 moles of NaCl are dissolved in 1.00 kg of water. What is the boiling point of this solution (kb = .512 degrees C·kg/mol for water) ?

What is the order of reaction for the following equation?A + B --> 2C

Calculate the bond dissociation energy in the following equation:CH4(g) + 2O2(g) --> CO2(g) + 2H20 (g) Given the following:DHf° C-H = 87 Kcal/molDHf° O=O = 118 Kcal/molDHf° C=O = 178 Kcal/molDHf° O-H = 111 Kcal/mol

Which of the following sets of quantum numbers is impossible for an electron?

Which of the following hybridizations would allow for the formation of one pi bond?

Find the pH of the a 0.500M solution of the weak base Ammonia (NH₃) . The K_b = 1.78*10^-5NH₃ +H₂O --> NH₄+ + OH^-

You have a closed container filled with 1L of pure air at STP. Assume that this air is made of only nitrogen (79%) and oxygen (21%) . What are the partial pressures of nitrogen and oxygen in the box?Hint: X_N = P_N/PTotal= N_N/N_Total

1) 75 moles of NaCl are dissolved in 1.00 kg of water. What is the boiling point of this solution (k_b = .512 degrees C·kg/mol for water) ?

Calculate the bond dissociation energy in the following equation:CH₄(g) + 2O₂(g) --> CO₂(g) + 2H₂0 (g) Given the following:DH_f° C-H = 87 Kcal/molDH_f° O=O = 118 Kcal/molDH_f° C=O = 178 Kcal/molDH_f° O-H = 111 Kcal/mol