chemistry problems with solution

7/23/2019 chemistry problems with solution

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LYCEUM OF THE PHILIPPINES UNIVERSITY - CAVITE CAMPUS

COLLEGE OF ENGINEERING, COMPUTER STUDIES AND ARCHITECTURE

DEPARTMENT OF ENGINEERING

CHEMISTRY

SUBMITTED BY:

GERONIMO, CHRISTINE ERICKA E.

BSECE-501

SUBMITTED TO:

ENGR. ARNEL M. AVELINO

DATE:

DECEMBER 05, 2015


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CHEMISTRY

1.) Book: Science HS.com Chemistry III

Question: What volume will the gas occupy at 760mmHg pressure, if 200mL sample of hydrogen is

collected when pressure is 860mmHg?

Solution: Given: P1 = 760mmHg

P2 = 860mmHg

V1 = 200mL

Find: V2 = ?

Soln: P1V1 = P2V2

V2 = =

Answer: V2 = 176.74 mL


Question: A 0.050 mole of hydrogen gas sample at a certain temperature and pressure occupies 4.0

L. How many moles of argon are there in a 2.0L container at that temperature andpressure?

Solution: Given: nH = 0.050 mole

VH = 4.0 L

VA = 2.0 L

Find: nA = ?

Vm = =

Vm = 80.2 L/mole

V = nVm

Answer: n = 0.025 moles


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Question: Ascorbic acid (Vitamin C) cures scurvy and may help prevent the common cold. Find its

empirical formula if it is composed of 40.92% carbon, 4.58% hydrogen and 54.50%

oxygen.

NC = 40.92g C x = 3.407mol C

= 3.407mol C 3.406 = 1(3) = 3

NH = 4.58g H x

= 4.54mol H

= 4.54mol H 3.406 = 1.33(3) = 3.99 or 4

NO = 54.50g O x = 3.406mol O

= 3.406mol O 3.406 = 1(3) = 3

Answer: Empirical Formula = C3H4O3


Question: What is the boiling point of a solution prepared by dissolving 2.50 g of biphenyl (C12H10)

in 85.0g of benzene? The molecular weight of biphenyl is 154g.

Solution: The molality solution is the number of moles of biphenyl dissolved in 1000g of benzene.

mol C12H10 = 1000g benzene

= 0.191

The molal boiling point elevation constant for benzene solution is 2.53C/m.

Tb = Kbm

= (2.53C/m) (0.191m)

= 0.483C

The normal boiling point of benzene is 80.1C. The boiling point of the solution,

therefore, is:

80.1C + 0.5C = 80.6C

Answer: 80.6C


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Question: How much C6H12O6is needed to prepare a 0.5m solution using 500g of water?

Solution: Given: mass solvent (H2O) = 500g

molality of solution = 0.5m

Formula: m =

mass solute =

mass solvent =

Soln: molality =

x

0.5 mole = x

mass solute = (0.50mole) (180g/mole) x

45g C6H12O6can be dissolved in 500g of waterAnswer: 45 g

6.) Site: http://chemistry.about.com/od/workedchemistryproblems/a/phstrongacid.htm

Question: Hydrobromic Acid (HBr) is a strong acid and will dissociate completely in water to H+

and Br-. For every mole of HBr, there wo;; be 1 mole of H +, so the concentration of H+

will be the same as the concentration of HBr. (H+ = 0.025M).

Solution: pH is calculated by the formula:

pH = - log (H+)

by entering the concentration found before:

pH = - log (0.025)pH = - (-1.602)

pH = 1.602

The pH pf a 0.025 M solution of Hydrobromic Acid is 1.602.

Answer: pH = 1.602


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7.) Site: http://chemistry.about.com/od/workedchemistryproblems/a/daltons-law-of-partial-

pressures.htm

Question: The pressure of a nitrogen (N), carbon dioxide (CO2), and oxygen (O2) is 150 kPa. What

is the partial pressure of oxygen if the partial pressures of the nitrogen and carbon dioxide

are 100kPa and 24kPa, respectively?

Solution: Daltons Law of partial pressure states that:

PTOTAL = P1 + P2 + P3 + ... Pn

Therefore,

PTOTAL = Pnitrogen + Pcarbon dioxide + Poxygen

150kPa = 100kPa + 24kPa + Poxygen

Poxygen = 150kPa - 100kPa - 24kPa

Answer: Poxygen = 26 kPa

8.) Site:

Question: 6.2 liters of an ideal gas are contained at 3.0 atm and 37C. How many moles of this gas

are present?

Solution: The ideal gas law states that:

PV = nRT

where:

P = pressure

V = volume

n = number of moles of gas

R = gas constant (0.08 L atm/mol K)

T = absolute temperature in Kelvin

Solution:

T = 37C + 273 K = 310 K

n = =

n = 0.75 mol

Therefore, there are 0.75 mol of the ideal gas present in the system.

Answer: n = 0.75 mol

http://chemistry.about.com/od/workedchemistryproblems/a/idealgasmoles.htm


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9.) Site: http://www.spiritsd.ca/curr_content/chem30_05/4_solutions/practice/a2_2.htm

Question: A 0.750 L aqueous solution contains 90.0 g of ethanol, C2H5OH. Calculate the molar

concentration of the solution in molL -1. (molar mass of C2H5OH = 46.1 gmol-1)

Solution: Volume = 0.750 L

Molarity =

= 90.0 g x

x

= 2.6 mol/L

Answer: [C2H5OH ] = 2.60M

10.) Site: http://www.chemteam.info/Solutions/Molarity-probs11-25.html

Question: What volume (in mL) of 12.0 M HCl is needed to contain 3.00 moles of HCl?

Solution:

12.0 M = 3.00 mol / x

x = 0.250 L

This calculates the volume in liters. Multiplying the answer by 1000 provides the

required mL value:

0.250 L x (1000 mL / L) = 250. mL (note use of explicit decimal point to create three sig

figs)

Answer: Volume = 250 mL


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Question: A process in which the form of certain properties of a substance change, but not its

chemical identity.

Answer: PHYSICAL CHANGE


Question: A solution concentration which is equal to the number of equivalents of solute per liter of

solution.

Answer: NORMALITY


Question: The attractive force existing between atoms or group of atoms that holds them together in

compounds and polyatomic ions.

Answer: CHEMICAL BOND


Question: An oxide or hydroxide of a metal which gives hydroxide ions in solution and neutralizes

an acid to a salt and water.

Answer: BASE


Question: The smallest particle of a pure substance which can exist by itself and carries all the

properties of that substance.

Answer: ATOM


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16.) Site: http://antoine.frostburg.edu/chem/senese/101/glossary.shtml

Question: This law states that when two pure substances react to form a compound, they do so in a

definite proportion by mass. For example, when water is formed from the reaction

between hydrogen and oxygen, the 'definite proportion' is 1 g of H for every 8 g of O.

Answer: LAW OF DEFINITE PROPORTIONS


Question: A branch of chemistry that quantitatively relates amounts of elements and compounds

involved in chemical reactions, based on the law of conservation of mass and the law of

definite proportions.

Answer: STOICHIOMETRY


Question: The temperature at which the volume of an ideal gas* becomes zero; a theoretical coldest

temperature that can be approached but never reached.

Answer: ABSOLUTE ZERO


Question: The volume of a gas is directly proportional to its temperature in Kelvin, if pressure and

amount of gas remain constant.

Answer: CHARLES LAW


Question: A measure of energy dispersal. Any spontaneous change disperses energy and increases

entropy overall. For example, when water evaporates, the internal energy of the water is

dispersed with the water vapor produced, corresponding to an increase in entropy.

Answer: ENTROPY


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BOOK REFERENCE:

Carigo, V., Fernandez, C., & Nudo, L. (2002). Science HS.com Chemistry III. Quezon City: Bookman, Inc.

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chemistry problems with solution