Chemistry Questions and Answers August 18, 2020

17. The boiling point of ethanol (C2H5OH) is 78.5 C. What is the boiling point of a solution of 6.4 g of vanillin (Mr 152.14 gmol) in 50.0 g of ethanol (Kb of ethanol 1.22 Cm)

18. The freezing point of benzene is 5.5 C. What is the freezing point of a solution of 5.00 g of naphthalene (C10H8) in 444 g of benzene (Kf of benzene 4.90 Cm)

19. In a study designed to prepare new gasolineresistant coatings, a polymer chemist dissolves 6.053 g of poly(vinyl alcohol) in enough water to make 100.0 mL of solution. At 25 C, the osmotic pressure of this solution is 0.272 atm. What is the molar mass of the polymer sample

For offices to feel comfortable, we like the relative humidity indoors to be about 50 and the temperature to be about 20C. An office is normally ventilated out side air flows through the office, where it is heated by a radiator. At the same time the office loses heat through the walls. We assume that the air properties in the office are

Determine the empirical formula of a hydrocarbon with hydrogen having a percentage composition of 14.3% and carbon having a percentage composition of 85.7%. (C=12; H=1)

On analysis it is discovered that a sample of an inorganic compound contains 23.4g of potassium and 0.3g of oxygen. If the relative molecular mass of the compound is 94, determine i. the empirical formula of the compound ii. the molecular formula of the compound. (K = 39; O = 16)

Differentiate between empirical formula and molecular formula.

Determine the molecular formula of a compound with empirical formula of CH if the relative molecular mass is 26.

The empirical formula of hydrogen peroxide, H2O2 is ________

Question: As Earth's climate changes, which features on Earth are expected to increase? A. Land area B. Greenhouse gases C. Freshwater reserves D. Sea ice

A zinc rod is placed in a 0.02 M ZnSO4 solution at 30 C. The E 0 of the half-cell is -0.76 V. If the ZnSO4 dissociation in the half cell is 80%, calculate the potential of Zn-electrode.

1) Calculate the number of moles of cations in 3 mmols/litre of solution of Na 2 SO 4. Assume complete ionization. a) 6 mmol/litre b) 3 mmol/liter c) 12 mmol/liter d) none of these

Borodium is a newly discovered transition metal . balance the following and determine the coefficient of H2 Bd + HF--> H 2 + BdF 3

D Question 7 Which of the following is a valid set of quantum numbers for an electron of highest energy for Pd (one of the last electrons to fill in) a. b. C. d. O b a O C 5 4 LO 5 5 1 2 2 0 4 mi 0 0 0 0 ms 1 pts

Draw the major organic product of the reaction shown. OH Select 2 G Draw Rings C H I More Erase 2 Q

The iron(III) chloride solution is initially clear and yellow while the potassium thiocyanate solution is initially clear and colorless. (4pts) For the reaction of iron(III) chloride and potassium thiocyanate, describe the reactant appearance and identify the evidence of chemical reaction. Then balance the chemical equation. Write out all

A venti coffee at Starbucks is 20 oz. If you want to convert this volume to ml, what conversion factor should be used in the dimensional analysis setup. 1 oz =30 mL A) 1 ml/30 oz B) 600 mL C) 1oz/30 mL D) 30 ml/1oz E) 1oz =30 mL

When a hydrated sample of calcium sulphate C a SO 4 , X H 2 O was heated until all the water was lost, the following data was recorded. Mass of crucible = 30.296g Mass of crucible + hydrated salt =33.111g Mass of crucible + anhydrous salt =32.781g Determine the empirical formula of the hydrated salt (relative formula mass of C a SO 4 =136, H+O=18)

1. Calculate the pH for the following solutions. (Since these are all buffers, you may use the HendersonHasselbalch equation) a. 10.0 mL 50 mM Tris 40.0 mL 50 mM TrisHCD b. 25.0 mL 50 mM Tris 25.0 mL 50 mM TrisHCD c. 25.0 mL 50 mM KHPO4 25.0 mL 50 mM Na2HPO4 TrisH K 8.51 x 109 H3PO4 2. What is the acid and base buffer capacity for each buffer

Which of the following solutions is acidic? A) [OH^-] = 1.0 x 10^-7 M B) [OH^-] > 1,0 x 10-7 M C) [OH^-] = 1.0 x 10^-10 M D) [H_3O^+] = 1.0 x 10^-10 M E) [H_3O^+] = 1.0 x 10^-7 M

Describe the utility of an ion-trap mass analyzer.

A compound X contains an ether functional group and shows a molecular ion peak at mz 72 in its mass I spectrum. Which is the possible structure for compound X 1. A. I and III B. I and V C. II and V D. III and IV Eye Which of the following molecules will show similar peaks in functional group region of an IR spectrum A. Br Br Which Newman

What are the factors upon which favorability of transport of a charged solute across the membrane depends?

Which of the following pairs do not constitute resonating structure (a) (c) MeN 0 and MeON0 09 and OH (b) Me CH and Me CH (d) MeCHCHMe and MeCHCHCH

Part A Which of the following condensed formulas correctly represents the lineangle structure shown below C(CH3)C(CH3)CH,CO,H CH(CH3)2CH(CH3)COH (CH3)2CC(CH3)CO,H C(CH3)3COH Submit My Answers Give Up

How to get the answer 0.091 For a diprotic acid HA, pKa, 4.00 and pka 9.00. What approximately would be the molar fraction of A2 in aqueous solution at pH 8.00 (Report your answer as a number with 2 sig. fig. Examples 0.50 or 0.055 or 0.0010) 0.10 0,091 x

D Question 10 Calculate the molecular mass of a protein if a 1.00 g sample is in a total volume of 1.53 mL at 37.0 C and 743 torr. 0163x10 mole 05.91x30mle O166x30 mole 01.70x30 gmole O203x30 gmole 10 pts

Sample B A1 A2 A3 B1 B2 83 C1 C2 C3 Beaker Mass Carbonate (8) Mass (g) 89.791 66.332 89.836 90.930g 65.071g 90.934g 90.442 65.071 90.478 0.507 0.509 0,499 0.503 10.501 0.505g 0.566 0.902 0.438 Product Mass Product Final Theoretical Beaker (g) Mass (g) Mass (g) 90.298 66.841 90.335 91.405g 65.601g 91.486 91.282 66.078 90.874 0.347 10.357 1.333

Equation above PARTS a. e. HSO4 2NaOH NaSO4 2HO An equation for the reaction that occurs during a titration lab is given above the task of titratine a 25ml sample of 0.25 M HSO4 with Question 3 (1 point) Hoved b. The equation above is not written in net ionic form. Wilte the correct net ionic equation for the reaction. 4 B I UN F 17 M THE Both

Lab question.

or 3 mL less than the total volume added in the first trial) to save time. 12. Repeat steps 10 and 11. You will have completed three trials after this step. Data Unknown 9D Mass of Sample 1 Mass of Sample 2 Mass of Sample 3 0.500 0.500 Molarity of standardized KMnO, solution 0.495 Sample Initial buret reading (mL) Final buret reading (mL) Initial

Explain each in short

In each of the reactions, how does the equilibrium respond to an increase in pressure (forward, backward, unchange) (a) 2 SO(g) O(g) 2 SO3(g) (b) H(g) 12(g) 2 HI(g) (e) 3 H(g) N(g) 2 NH3(g) Equilibrium shift Equilibrium shift Equilibrium shift

In acid solution the following are true under the standard conditions. (a) HS will react with oxygen to give HO and sulphur. (b) HS will not react in the corresponding reaction with selenium and tellurium. (c) HSe will react with sulphur giving to HS and Se but not react with tellurium. Arrange the hydrides HO, HS, HSe and HTe in order of their

Answer whether under standard conditions the following reactions are possible or not. (1) Will Fe reduce Fe to Fe (ii) Will the permanganate ion MnO4 liberate O from water in the presence of an acid (ii) Will O oxidize gold to Au(CN) in the presence of CN and OH ions (iv) Would you use silver spoon to stir a solution of Cu(NO3) (v) Will ceric

Ascertain, with a little calculation, whether or not each of the following reactions will proceed to the forward or backward direction at 25 C when all concentrations and pressures are unity. (a) 2Cr 3Cu2Cr 3Cu (c) Fe Cl(g) Fe 2Cl (e) 2Ag Cu 2Ag Cu (b) Zn Mg Zn Mg (d) 2Fe Cl(g) 2Fe 2Cl (f) 2Ag Cu 2C12AgCl(s) Cu

(a) Which of the following halfreactions will oxidize Cu(s) to Cu under standard conditions (i) Cl(g) to CI (ii) MnO, (aq) to Mn (aq) (iii) Ag to Ag. (b) Which of the following halfreactions will reduce Fe to Fe under standard conditions (i) Sn to Sn (ii) Mn (aq) to MnO2 (aq) (iii) Pb(s) to Pb (aq)

The four elements W, X, Y, Z form diatomic molecules and also form singly charged negative ions. The following observations are made in a series of experiments (b) 2W Y No reaction (a) 2X Y2Y X (c) 2Z X 2X Z Use these observations to write equation for each halfreaction. Arrange them in the decreasing reduction potential series. Which ion

Sometimes a species in a given oxidation state undergoes selfoxidation reduction reaction (disproportionation) in aqueous medium to give products of lower and higher oxidation states. For example, when Br is added in an alkaline solution (OH 1 mol dm), it disproportionates to give bromide and hypobromide ions. Rationalize the above results from

Determine the cell reaction and Ecell for each of the following cells at 25 C. Assume activity and fugacity equal to molar concentration and pressure (bar), respectively. (1) Mg Mgl(0.1 mol dm) 1(s) Pt (i) Ag AgBr(s) HBr(0.02 mol dm3) H,(0.5 bar) Pt (iii) Fe Fe(NO3) (0.05 mol dm) Cu(NO3)(0.01 mol dm) Cu (iv) Pt H(g, 0.127 bar) HCI

The emf of the cell Hg Mercurous nitrate (0.01 M) Mercurous nitrate (0.1 M) Hg is found to be 0.029 5 V at 25 C. Determine the molecular formula of mercurous nitrate.

Explain Types of Adsorption.

A cell consists of a Pt electrode immersed in the redox system A A ne is combined with a saturated calomel electrode (rightside electrode). From the following data at 303 K, determine the value of n. Per cent of reduced form erfV 0.101 0.116 0.129 The standard potential of the calomel electrode at 303 K is 0.238 V. 24.4 48.8 73.2 84.5 0.139

Calculate E for the following reactions at 298 K. Ag(NH3) Ag 2NH3,Given Ag(CN)2eAg 2CN Eg Ag 0.799 1 V, Kins(Ag(CN)) 1.995 101. Kins (Ag(NH3)2) 6.02 x 10 and

Show that the standard potential of the reaction HOeH OH is given as RT In Kw Determine its value at 298 K.

From the standard potentials shown in the following diagram, calculate the potentials E and E. BrO3 0.54 V Ei Bro 0.45 V 25 1.07 V Br 0.76 V Br

Calculate the potential at 25 C for the cell Pt H(p 1 bar) HBr(a 0.2) HgBr(s) Hg

The potential of the cell Cd Cdl(a) Agl(s) Ag is 0.286 0. V at 25 C. Calculate the mean ionic activity of the ions in the solution, and the activity of electrolyte.

The potential of the cell Zn(s) ZnCl(0,010 21 mol kg ) AgCl(s) Ag(s) is found to be 1.156 6 V. What is the mean ionic activity coefficient of ZnCl in the solution

The emf of the cell Ag AgCl(s) KCl(aq) HgCl(s) Hg is 0.045 5 V at 298 K and the temperature coefficient is 3.38 x 104 V K. What is the reaction taking place in the cell and what are free energy, enthalpy and entropy changes at 298 K

At 298 K, the emf of the cell Hg 0.01 mol dm KCI 1 mol dm3 KNO3 sat. with HgCl salt bridge 0.01 mol dm KOH sat. with HgO Hg is found to be 0.163 4 V and the temperature coefficient of the emf to be 0.000 837 V K. Calculate the enthalpy and entropy changes of the reaction. What is the reaction that occurs in the cell

For the cell Ag(s) AgBr(s) KBr(aq) Hg,Br,(s) Hg(l) the emfs at several temperatures are TK 293 emfV 0.066 3 298 0.0683 9 (a) Write the cell reaction for the passage of twofaraday of charge. (b) Calculate AG, AH and AS at 298 K. 303 0.0704 8

For the following cell Pb PbCl(s) PbCl(soln.) AgCl(s) Ag the potential at 298 K is 0.490 V and the variation of emf with temperature is given by E a (1.86 x 104 V K) (T25 K) Write the equation for the cell reaction and calculate AG, AH and AS for the reaction at 298 K.

At 273 K, the calorimetric determination of AH for the reaction Zn(s) 2AgCl(s) ZnCl(aq) Ag(s) yielded 217.78 kJ mol, while the emf of the corresponding cell was 1.015 V. What was (JEOT), of the cell

(a) At 298 K the standard free energy of formation of HO(1) is237.23 kJ mol, while that of its ionization to hydrogen and hydroxyl ions is 79.71 kJ mol. What will be the reversible emf at 298 K of the cell,Pt H(g. 1 bar) H(1 M) OH(1 M) O(g. 1 bar) Pt (b) The enthalpy of formation at 298 K of HO(1) is 285.85 kJ mol, while its enthalpy of

Determine the standard equilibrium constant of the following reaction at 298 K. 2Fe Sn2Fe Sn

Determine the standard equilibrium constant of the following reaction at 298 K. 2MnO4 6H 5HCO4 2Mn 8HO 10C0

Determine the standard equilibrium constant of the following reaction at 298 K. Cd2 4NH, C(NH),)

Determine the standard equilibrium constant of the following reaction at 298 K. Cu(OH) Cu(aq) 2OH(aq)

How would you use the arrangement Ag Agl(sat. soln.) Agl(s) Ag to measure the solubility product of silver iodide at 298 K

An excess of solid AgCl is added to a 0.1 mol dm3 solution of Br ions. Assuming activity equal to ionic concentration, calculate the concentration of CT and Br ions at equilibrium.

Compute the equilibrium constant of the following reaction at 298 K Zn Cu Zn Cu

The following emfs refer to the cell at 298 K Pt H(1 bar) LiOH(0.01 mol dm3), LiCl(m) AgCl(s) Ag 0.01 1.049 5 mmol dm EIV 0.02 1.031 5 0.05 1.007 3 0.10 0.988 5 0.20 0.969 4 The standard potential of silversilver chloride halfcell is 0.222 5 V. Determine the ionic product of water.

Determine at 298 K for the cell Pt Q, QH, H (a) its emf when pH 5.0, (b) the pH when Ecell 0, (c) the positive electrode when pH 7.5. 1 M KCl HgCl(s) Hg(1) Pt

In a cell consisting of glass electrode in solution with pH of 7.0 and a calomel electrode, the emf of glass electrode at 298 K was 0.062 V. When a solution of unknown pH replaced the standard buffer, the glass electrode potential was 0.145 V with the glass electrode negative. Calculate the unknown pH if during caliberation, the glass electrode

Find the cell reaction and calculate the potential of the following cell at 298 K. Cd(s) CdS0 (0.01 mol kg, y 0.383), PbSO4(s) Pb Pb PbSO4(s), CdSO (1.00 mol kg, y 0.042) Cd(s) T e

Show that the emf of the cell M(s) MX(a) AX (s) A AX(s) MX,(a,) M(s) is given by RT () (4) E In

Calculate the potential at 298 K of the following cell. Zn ZnCl(m 0.01 mol kg, y 0.708) AgCl Ag AgCi ZnCl(m 0.10 mol kg, 0.502) Zn

Given the cell Cd Cd(OH)(s) NaOH(0.01 mol kg ) H(1 bar) Pt with Ecel 0.0 V at 298 K. If Ecacd0.40 V. Calculate (a) K for Cd(OH)2, and (b) AG, AS and AH for the cell reaction if (ET), 0.002 V K.

When metallic copper is shaken with a solution of a copper salt, the reaction Cu Cu 2Cu proceeds. When equilibrium is established at 298 K, CuCu 1.66 x 106 (mol dm). If the standard potential of the Cu Cu half cell is 0.337 V, what is the standard (reduction) potential of Cu Cu halfcell

When silver chloride is dissolved in a large excess of ammonia, practicaly all silver can be assumed to exist as Ag(NH3). Compute the values of m and n using the following two cells Ag 0.379 x 10 M AgCl, 1 M NH, 37.9 x 103 M AgCl, 1 M NH Ag Ecell 0.118 5 V at 298 K Ag 3.4 x 10 M AgCl, 1 M NH 3.4 x 103 M AgCl, 0.1 M NH3 Ag Ecell 0.126 3 V at

The emf of the cell Pt H(g) (p 1 bar) HA,(0.1 M) HA(0.1 M), QH, Q Pt is found to be 0.731 4 V at 298 K, where HA, and HA are two monoprotic weak acids. Answer the following (a) Which of the two acids is stronger (b) How many times is it stronger (c) If the dissociation constant of the stronger acid is 2.1 x 10 mol dm, calculate the

Determine the degree of hydrolysis and hydrolysis constant of anilinium hydrochloride in M32 solution of salt at 298 K from the following cell data at 298 K M Pt H(1 bar) H(a 1) 32 CHNHHC1 soln. H(1 bar) Pt Ecell 0.188 V.

The standard potentials of the two halfcells A, A Pt and B, B Pt are Ej and E, respectively. If E2 is greater than E, answer the following. (i) The cell Pt A(m), A()(km) B)(n), B(kn) Pt,was constructed, where k has some constant value. The cell was operated reversibly up to its exhaustion point, i.e. to a point where no more reaction in the

What are the three functional groups in the molecule

how do i solve this 5. Consider the following reaction, where X represents an unknown element 6X(s) 2B203(s)B4X3(s) 3XO2(g) If 155 grams of X reacts completely with diboron trioxide to produce 2.15 mol of B4X3, what is the identity of X 2.15184x3 12.9 1 ac b. Mg c. Ge d. Si e. N 1 the options are a. C b.Mg c. Ge d. Si e. N 13

A student titrated a 10.00 mL sample of vinegar with 0.187 M NaOH. The student analyzed their titration curve and summarized their data in the following table. Region Initial Half Equivalence point Equivalence point PostEquivalence point Measured pH 2.74 4.69 8.18 12.11 Total volume of titrant (ml) 0.00 19.40 38.80 50.00 Total volume of solution

Heat of Solution 1. Weigh the cleaned and dried calorimeter and record mass below 2. Place about 50ml. of distilled water in calorimeter and weigh and record below 3. Measure the water in the calorimeter (original temp of water) and record below 4. Weigh out approx. 5g of solid assigned (record unknown ) in a metal weighing pan and record mass

2 A water sample has 61 mgL HCO and 100 mgL CO The pH of water ample is 9. The temperature of water is 25c. what is the alkanity of the watee 8emple in milli equivalent L. Mass concentrations of Caloz in mgL for the alkanity you calculated

A 10.00 L tank at 27.1 Ces filled with 16.6 g of dinitrogen dfluoride gas and 2.29 g of chlonne pentauonde gas. You can assume both gases behave as ideal gases under these conditions Calculate the mole fraction of each gas. Round each of your answers to 3 s Groofide perta mole fraction 0 to 3 significant digts 0 SER

How bad of an alcoholic do you have to be to have your brain affected?

1. Given a 100mL water sample required 18mL 0.04 N sulfuric acid to reach the methyl orange endpoint (at pH 4.3), and that the same volume of water required 20mL standard 0.02 N EDTA to reach the EBT endpoint (from red to blue), report (a) The total hardness (TH) in mgL as CaCO3 (b) The total alkalinity (TAlk) in mgL as CaCO, (c) The carbonate

Calculate the molarity of NaOH in the solution prepared by dissolving its 4g in enough water to Porm 250 mL of solution.

Assign the H NMR spectrum of acetophenone CDC13

A compound is found to be 53 Al and 47 O. Find its empirical formula.

if Al 2 O 3 had molecular weight of 306g, what would be the molecular formula of the compound?

Which substance is not correctly matched with its identity? a. Water compound b. Sodium chloride heterogeneous mixture c. Helium monatomic element d. Air homogenous mixture e. Oxygen diatomic element

Consider the ionic compound XCl2 where X represents some unknown element. Which could not be a possible name for the compound XCl2? a. Calcium chloride b. Magnesium chloride c. Manganese(II) chloride d. Sulfur dichloride e. Copper(I) chloride

Consider an aluminum ion with formula below: Which of the following has the same number of protons as this ion? a. A neutral atom of aluminum. b. A neutral atom of neon. c. A stable ion of fluorine. d. Two of the above (a.-c.) have the same number of protons as this ion. e. All of the above (a.-c.) have the same number of protons as this ion

27 13 A13

Which of the following is not an assumption we make about ideal gases and their behavior according to kinetic molecular theory? a. Gas particles are in constant random motion. b. While the gas itself may take up significant space, the volume of the gas particles themselves do not take up significant space. c. A gas sample of neon and a gas sample

. A rigid steel tank holds 20.0 grams of helium gas at some temperature. The pressure of the helium in the container is 10.0 atm. 20.0 grams of neon gas is added to the container. What is the total pressure in the container after the neon gas is added? a. Less than 10.0 atm b. Exactly 10.0 atm c. Between 10.0 atm and 20.0 atm d. Exactly 20.0 atm

Give the molecular formula of this compound, showing all necessary work and calculations. Does it have the same molecular formula as either of the compounds in part a) If so, identify which one. If not, explain why not.

A compound is found to contain 63.52 iron and 36.48 sulfur. Find its empirical formula.

A compound is found to contain 26.56 potassium, 35.41 chromium, and the remainder oxygen. Find its empirical formula.

A 60.00 g sample of tetraethyllead, a gasoline additive, is found to contain 38.43 g lead, 17.83 g carbon, and 3.74 g hydrogen. Find its empirical formula.

A 170.00 g sample of an unidentified compound contains 29.84 g sodium, 67.49 g chromium, and 72.67 g oxygen. Find the empirical formula.

Determine the molecular formula of the compound with an empirical formula of CH and a formula mass of 78.110 u.

. Determine the molecular formula of a compound with an empirical formula of NH and a formula mass of 32.06 u.

A sample of a compound with a formula mass of 34.00 u is found to consist of 0.44 g H and 6.92 g O. Find its molecular formula.

3.20 g of oxygen gas contains A. 0.200 mol O2 molecules B. 0.100 mol O atoms C. 0.100 mol O2 molecules D. 0.0500 mol O atoms

The number of H atoms in 0.20 mol CH4(g) is A. 1.2x1023 B. 4.8x1023 C. 3.0x1024 D. 1.2x1025

What is the total number of atoms present in 0.0100 mol of propane, C3H8? A. 6.02 x1021 B. 5.47x1020 C. 6.62x1022 D. 1.02x1023