WorksheetsChem 0100 Q1
Total questions: 20
Worksheet time: 3600secs
Hydrogen peroxide, H2O2, decomposes at 25°C to yield water and oxygen. Write the balanced equation for this reaction.
2H2O2(l) → H2O(g) + O2(g)
H2O2(l) → H2O(g) + O2(g)
2H2O2(l) → 2H2O(l) + O2(g)
2H2O2(l) → 2H2O(g) + O2(g)
What volume of water will be produced from the complete decomposition of 5 mL of H2O2? (Ar: H = 1; O = 16) Density of H2O2 = 1.450 gcm-3; H2O = 1.00 gcm-3)
3.8 mL
24 cm3
16 mL
2.5 cm3
0.0012 moles of Na2CO3 were dissolved in distilled water in a 250.0 mL volumetric flask, and the solution made up to the mark. A 25.0 mL aliquot was taken and 40 mL of an HCl solution of unknown concentration was added. This resulting mixture required 16.5 mL of a 0.12 M NaOH solution for complete neutralization. (i) Why is Na2CO3 a primary standard?
It is impure.
It absorbs carbon dioxide from the atmosphere.
It absorbs water from the atmosphere.
It is stable and hence the strength does not change with time.
Give two specific reasons why NaOH is not considered to be a primary standard.
It absorbs water from the atmosphere changes it's mass.
It is not pure because it reacts with carbon dioxide on exposure to air.
NaOH is used as a primary standard.
NaOH has a high weight.
What is meant by the term "back titration"?
Calculating the amount of solute required and making up the solution by dissolving this amount.
Titrating original sample using a standard solution.
Titrating excess standard reagent.
Diluting a higher concentration to make a less concentration one.
Write the balanced equation for the reaction between Na2CO3 and HCl.
Na2CO3(aq) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + HCl(aq)
2Na2CO3(aq) + HCl(aq) → 4NaCl(aq) + CO2(g) + H2O(l)
Na2CO3(s) + 2HCl(aq) → 4NaCl(aq) + CO2(g) + H2O(l)
Na2CO3(aq) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l)
0.0012 moles of Na2CO3 were dissolved in water in a 250.0 mL volumetric flask, and the solution made up to the mark. A 25.0 mL aliquot was taken and 40 mL of HCl solution of unknown concentration was added. This resulting mixture required 16.5 mL of a 0.12 M NaOH solution for complete neutralization. Calculate the number of moles of HCl that reacted with the 25.0 mL aliquot of the Na2CO3(aq).
0.0012 moles HCl
0.0024 moles HCl
0.00012 mol HCl
0.00024 mol HCl
0.0012 moles of Na2CO3 were dissolved in water in a 250.0 mL volumetric flask, and the solution made up to the mark. A 25.0 mL aliquot was taken and 40 mL of HCl solution of unknown concentration was added. This resulting mixture required 16.5 mL of a 0.12 M NaOH solution for complete neutralization. Calculate the number of moles of HCl that reacted with the NaOH.
0.12 mol/16.5 mL
(16.5 mL x 0.12 mol)/1000 mL
0.12 mol/1000 mL
(0.12 mol/ 16.5 mL) x 1000 mL
0.0012 moles of Na2CO3 were dissolved in water in a 250.0 mL volumetric flask, and the solution made up to the mark. A 25.0 mL aliquot was taken and 40 mL of HCl solution of unknown concentration was added. This resulting mixture required 16.5 mL of a 0.12 M NaOH solution for complete neutralization. Calculate the molarity of the HCl(aq).
0.06 M HCl solution
0.00006 M HCl solution
0.00222 M HCl solution
0.00198 M HCl solution
Calculate the energy required to excite an electron from the n = 2 to the n = 4 level in atomic hydrogen. What is the maximum wavelength of light that causes this excitation?
4.09 x 10-19 J, 486 nm
4.09 x 10-18 J, 426 nm
2.09 x 10-18 J, 496 nm
2.09 x 10-19 J, 506 nm
The mass of a neutron is 1.67 x 10-27 kg. What is the wavelength of a neutron moving at a speed of 4.21 x 103 ms-1?
900 nm
0.9 nm
0.09 nm
90 nm
Which of the following sets of four quantum numbers (n, l, m, s) are not allowed for an electron in an atom?
(4, 2, 2, +1/2)
(4, 2, 1, -1/2)
(4, 1, 0, - 1/2)
(4, 2, 3, +1/2)
Calculate the energy, frequency and wavelength for the electron transition from n=1 to n=5 in the hydrogen atom.
2.09 x 10-19 J, 3.16 x 1015 s, 9.5 x 10-8 s
2.09 x 10-18 J, 3.16 x 1015 s-1, 9.5 x 10-8 m
4.09 x 10-18 J, 3.16 x 1015 s, 950 nm
2.09 x 10-18 J, 3.16 x 1015 s-1, 95 ns
One electron has the set of quantum numbers n=3, l=1, ml= -1 and ms = +1/2; another electron has the set n=3, l=1, ml=1 and ms= +1/2. Could the electrons be in the same orbital? Explain.
No they could not be because they have the same spin.
Yes they could be in the same orbital because the orbital number is 3.
Yes the could be in the same orbital because the orbital number is 1.
No they cannot be in the same orbital because they are not in the same atom.
Calculate the uncertainty in the position of an electron moving at a speed of (3.00 +/- 0.01) x 105 m/s. The mass of an electron is 9.11 x 10-31 kg.
580 x 10-8 m
0.58 x 10-8 m
58 x 10-8 m
5.8 x 10-8 m
The wavelength of light required to dissociate a chlorine molecules is 493 nm. Calculate the energy needed to dissociate 2 moles of chlorine molecules into chlorine atoms.
486 kJ
4.86 kJ
48,600 J
4.86 J
Which element has the highest ionization energy: Mg, Be or Ca?
Mg
Be
Ca
none of the above
Arrange the following ions in order of decreasing radius.
Na+ > Mg2+ > Al3+
Al3+ > Mg2+ > Na+
Na+ > Al3+ > Mg2+
Al3+ > Na+ > Mg2+
You wish to determine the molar composition of base in an antacid sample. The powered antacid sample is placed in a conical flask to which 50 mL of 0.15 M HCl is then added. The mixture is heated on a hotplate until complete dissolution. The resulting solution required 17.50 mL of 0.1 M NaOH for complete neutralization, using phenolphthalein as an indicator. The composition of base in the antacid can be described by the formula given below: 4MgCO3.Mg(OH)2.4H2O. Calculate the individual number of moles of magnesium carbonate and magnesium hydroxide in the antacid sample?
1.44 x 10-3 moles of each
5.75 x 10-3 moles of each
2.88 x 10-3 moles of each
4 moles of each
Chlorine has an atomic mass of 35.45 and consists of two stable isotopes 35Cl, mass = 34.969 gmol-1 and 37Cl, mass = 36.966 gmol-1. What are the percent abundances of the two isotopes in natural chlorine?
65% 35Cl, 35% 37Cl,
76% 35Cl, 24% 37Cl,
75% 35Cl, 25% 37Cl,
55% 35Cl, 45% 37Cl,
