Lecture 1 - Stoichemetry Flashcards
Which of the following statements about amount of substance is FALSE?
(A) The S.I. unit for amount of substance is mol.
(B) Amount of substance can be determined by dividing the mass of the substance by the molar mass of the substance.
(C) One mole of gaseous helium (He(g)) contains 6.022×1023 atoms (The Avogadro constant L = 6.022×1023 mol-1).
(D) One mole of hydrogen molecules contains twice as many particles as one mole of hydrogen atoms.
(D) One mole of hydrogen molecules contains twice as many particles as one mole of hydrogen atoms.
They are equal.
Which of the following statements about amount of substance is INCORRECT?
(A) Molar mass (M) is the mass of 1 mole of a specified entity.
(B) One mole is the amount of substance that contains the same number of specified entities as there are atoms in exactly 12 g of the carbon isotope 12C.
(C) One mole of gaseous hydrogen molecules, H2(g), contains 6.022 × 1023 molecules of hydrogen (Avogadro constant L = 6.022 × 1023 mol-1).
(D) One mole of hydrogen molecules and one mole of helium atoms have the same mass.
(D) One mole of hydrogen molecules and one mole of helium atoms have the same mass.
The Haber reaction uses N2(g) and H2(g) to make artificial fertiliser (NH3(g)) as follows:
N2(g) + 3H2(g) → 2NH3(g)
If the reaction goes to completion, what mass of ammonia NH3 will be produced from 2.00 g H2?
(A) 11.3 g
(B) 22.5 g
(C) 25.4 g
(D) 33.8 g
(A) 11.3 g
The Haber reaction is used to make ammonia, NH3(g), for artificial fertilizers N2(g) + 3H2(g) → 2NH3(g)
What is the maximum amount of ammonia, NH3, that can be produced by the reaction of 1.0 mol N2 and 1.0 mol H2?
(A) 2 mol
(B) 2/3 mol
(C) 1/2 mol
(D) 3/2 mol
(B) 2/3 mol
Since the stoichiometry of the reaction is 1:3 for N2 to H2, and we have equal moles of N2 and H2, H2 is the limiting reactant.
For every 3 moles of H2, 2 moles of NH3 are produced.
So, if we have 1 mole of H2, the maximum amount of NH3 produced would be:
Moles of NH3 = 1.0 mols of H2 x (2 mol of NH3 / 3 mol H2)
Moles of NH3 = 1 x 2/3
Moles of NH3 = 2/3 mol
Therefore, the maximum amount of NH3 that can be produced by the reaction of 1.0 mol N2 and 1.0 mol H2 is 2/3 moles of NH3
What is the concentration of Cl- ions in a solution of 0.50 mol L-1 AlCl3 solution?
A) 0.50 mol L-1
B) 1.0 mol L-1
C) 0.15 mol L-1
D) 1.5 mol L-1
D) 1.5 mol L-1
For every 1 mole of AlCl3 that dissociates, it produces 3 moles of Cl- ions.
Given that the concentration of the AlCl3 solution is 0.50 mol/L, and AlCl3 produces 3 moles of Cl- ions for every 1 mole of AlCl3
3 x 0.5 = 1.5 mol L-1
What amount of nitrogen gas (N2(g)) is there in a sample weighing 21 g ?
A) 1.0 mol
B) 3.0 mol
C) 0.75 mol
D) 1.5 mol
C) 0.75 mol
2 x 14 = 28 gmol-1
n = m/M
n = 21/28
n = 0.75 mol
How many atoms of oxygen are represented by the notation 3Mg(OH)2?
6
3 x 2
T or F
We balance chemical equations as we do because energy must be conserved
False
We use it to follow the law of conservation mass
T or F
If the reaction 2O3 → 3O2 goes to completion and all of O3 is converted to O2, then the mass of O3 at the beginning of the reaction must be the same as the mass of O2 at the end of the reaction
True
T or F
You can balance the “water splitting” reaction H20 → H2 + O2 by writing it this way: H202 → H2 + O2
False
“Atoms are neither created or destroyed in a reaction” - Law of conservation mass
NaCl with sulfuric acid, H2SO4, to produce sodium sulfate, Na2SO4, as described by the
following equation:
2NaCl + H2SO4 → Na2SO4 + 2HCl
Which of the following statements about this reaction, when it goes to completion, is INCORRECT?
(A) When 2 moles of NaCl react, 2 moles of HCl are produced.
(B) When 5 moles of H2SO4 react, 10 moles of HCl are produced.
(C) When 1 mole of NaCl reacts, 2 moles of Na2SO4 are produced.
(D) When 4 moles of Na2SO4 are produced, 8 moles of HCl are produced.
(B) When 5 moles of H2SO4 react, 10 moles of HCl are produced.
