Moodle  : Chemistry Tests

blueline

Topic 1: Stoichiometry

  1. Answer the following questions:
    1. figure out the mass (in g) of the following elements,
      1. 2 mol. of lithium
      2. 3 mol. or magnesium
    2. figure out the number of moles of the following elements,
      1. 48g or carbon
      2. 46g of sodium
    3. figure out the mass (in g) of the following compounds,
      1. 2 mol. of water (H2O)
      2. 3 mol. of ethane (C2H6)
    4. figure out the number of moles of the following compounds,
      1. 64g of methanol (CH3OH)
      2. 22g of carbon dioxide (CO2)
  2. Answer the following:
    1. figure the number of moles of the following compounds with data given,
      1. 30 cm3 of 0.5 mol/dm3 concentration hydrochloric acid (HCl)
      2. 10 dm3 of 0.1 mol/dm3 concentration sulfuric acid (H2SO4)
      3. 100 cm3 of oxygen (O2) at standard condition (1 atm, 298K)
      4. 500 cm3 of nitrogen dioxide (NH2) at 1 atm and 273K
    2. describe a method to calculate the density of a liquid in a experiment
    3. state a general formula for the density of a liquid.

Answers from last week:

  1. n = m/M
      1. 2 = m/7
        m = 14 g
      2. 3 = m/24
        m = 72 g
      1. n = 48 / 12
        n = 4 mol.
      2. n = 46 / 23
        n = 2 mol.
      1. 2 = m / 18
        m = 32 g
      2. 3 = m / 30
        m = 90 g
    1. d)
      1. n = 64 / 32
        n = 2 mol.
      2. n = 22 / 44
        n = 0.5 mol.
      1. n = cv
        n = 0.5 x (30/1000)
        n = 1.5 x 10-2 mol.
      2. n = 0.1 x 10
        n = 1 mol.
      3. n = v / 24000
        n = 100 / 24000
        n = 1 / 240 mol.
      4. n = v / 22400
        n = 500 / 22400
        n = 5 / 224 mol.
    1. b) Measure the mass of a known pure liquid with a known volume.
    2. c) density (g/cm3) = mass (g) / volume (cm3)

This week's quiz:

1. Define the term, 'Isotopes'.

2. Spectra have been used to study the arangements of electrons in atoms. An emission spectrum consists of a series of bright lines that converge at high frequencies. Such emission spectra provide evidence that electrons are moving from

A.lower to higher energy levels with the higher energy levels being closer together. B.lower to higher energy levels withe lower nergy levels being closer together. C.higher to lower energy levels with the lower energy levels being closer together. D.higher to lower energy levels with the higher energy lebels being closer together.

3. Which electron transition in a hydrogen atom releases the most energy?

A. n=2 to n=1

B. n=4 to n=2

C. n=6 to n=3

D. n=7 to n=6

The following questions are for people taking higher level course.

4. All of the following factors affect the value of the ionisation energy of an atom except the

A.mass of the atom

B.charge on the nucleus

C.size of the atom

D.main energy level from which the electron is removed

5.The first four ionisation energies (kJ mol-1) for a particular element are 550, 1064, 4210, and 5500 respectively. This element should be placed in the same Group as

A. Lithium

B. Beryllium

C. Boron

D. Carbon