1. Mole concept and stoichiometry

Question 1

define relative atomic / isotopic / molecular / formula mass

Answer 1

weighted av mass of ________compared to 1/12 the mass of a ¹²C atom

atomic: an atom of the element
isotopic: the isotope
molecular: the molecule of the element/compound
formula: formula unit of the compound

Question 2

balanced combustion eqn

Answer 2

CₓHᵧ + (x + ʸ/₄) O₂ –>
xCO₂ + ʸ/₂ H₂O

Question 3

formula for combustion

Answer 3

contraction = init - final

Question 4

20 hydrocarbon + 150 O₂
contraction 60
further contraction 80 when subjected to NaOH
whats the formula

Answer 4

contraction = V(CₓHᵧ) + V(O₂ reacted) - V (CO₂)
60 = 20 + V(O₂ reacted) - 80
V(O₂ reacted) = 120

1/x = 20/80 –> x = 4
1/(x + ʸ/₄) = 20/80 –> y = 8

Question 5

do u rem what is volume strength

Answer 5

V(O₂) produced in cm³ when 2cm³ of H₂O₂ completely decomposes at rtp

Question 6

determine Vol strength of (a mol dm⁻³) H₂O₂ at rtp

Answer 6

n(O₂) from 1dm³ H₂O₂ = 0.5a
n(O₂) from 1cm³ H₂O₂ = 5a x 10⁻⁴
V(O₂) = 5a x 10⁻⁴ x 24000

vol strength is __ volume

Question 7

which phases will occur with
A. NaOH, NaHCO₃
B. NaOH, Na₂CO₃
C. Na₂CO₃, NaHCO₃

Answer 7

A) 1. NaOH >
2. NaHCO₃ >
B) 1. NaOH >
Na₂CO₃ > NaHCO₃
2. NaHCO₃ >
C) 1. Na₂CO₃ > NaHCO₃
2. both NaHCO₃ >