1. A mixture of two sugars was compared with four different sugars using chromatography. The results are shown in the chromatogram below.

Which two sugars does this mixture contain?

                    

• A. 1 and 2

• B. 1 and 4  

•   C. 2 and 3

•        D. 2 and 4

Answer explanation

Chromatography is used to separate mixtures of substances into their components. All forms of chromatography work on the same principle.

They all have a stationary phase (a solid, or a liquid supported on a solid) and a mobile phase (a liquid or a gas).

The mobile phase flows through the stationary phase and carries the components of the mixture with it.

Different components travel at different rates

2. A bottle of copper (II) oxide has been contaminated with some solid sodium chloride. How can sodium chloride be removed from copper (II) oxide?

• A. heat the mixture and allow it to cool.

• B. add dilute acid to the mixture and filter

• C. place the mixture in a separating filter

• D. adding excess water to the mixture and filter.

Answer explanation

Copper (II) oxide is insoluble in water, while sodium chloride (a neutral salt) is completely soluble in water. So, by rinsing copper (II) oxide with water can dissolve and remove the sodium chloride from it.

3. The table below shows some of the properties of four elements. Which element is most likely to be a transition metal?

• Element A

• Element B

• Element C

• Element D

Answer explanation

Properties of transition elements include:

have large charge/radius ratio;

are hard and have high densities;

have high melting and boiling points;

form compounds which are often paramagnetic;

show variable oxidation states;

form colored ions and compounds

4. In the Periodic Table below, each number represents an element in the Periodic Table.

Which two numbers represent non-metals in the same group?

• A. 1 and 2

• B. 3 and 8

• C. 4 and 9

• D. 6 and 7

Answer explanation

Both elements belong under Group 16 which indicates places for O and S which are both non metals.

5. The diagram shows metal X reacting with water.

Which of the following could X be?

                                                            

• A. Calcium       

• B. Copper   

• C. Potassium

• D. Tin

Answer explanation

Potassium (Group I) - Very Reactive with water.

2K + H_²O --> 2KOH + H₂ + Heat (Exothermic reaction)

Copper (Transition): Metals such as lead, copper, silver and gold do not react with water at all.

Tin (Group XIV):Tin is an unreactive metal in general. The element tin forms a protective oxide layer that resists further oxidation in air.

6. Four identical gas jars are filled with different gases. The lids are taken off the gas jars, and they are left open to the air for a few hours. Which gas jar will then have the most air in it?

• 
• 
• 
• 

Answer explanation

nitrogen (formula: N₂ ) = 14.0 + 14.0 = 28.0

oxygen (formula: O₂ ) = 16.0 + 16.0 = 32.0

ammonia (formula: NH₃ ) = 14.0 + 1.0 + 1.0 + 1.0 = 17.0 The sulfur dioxide (formula: SO₂ ) = 32.0 + 16.0 + 16.0 = 64.0 Ammonia has the smallest relative molecular mass and will therefore diffuse out of the gas jar faster than the other three gases. As the ammonia diffuses out of the gas jar, air will take its place.

7. Rick found an unknown element. He later discovered that it has 6 electrons more than a sodium atom. What could the element be?

• A. Chlorine      

• B. Nitrogen         

• C. Iron

• D. Argon

Answer explanation

Atomic No. of Sodium is 11

11+6 electrons = 17

Element No. 17 = Chlorine

8. Which of the following represents the isotope chlorine-37?

•  

  A.

  Atomic Number: 17

  Composition:

  37 protons, 17 neutrons

  Atomic Mass: 37

• B.

  Atomic Number: 17

  Composition:

  37 protons,18 neutrons

  Atomic Mass: 37

• C

  Atomic Number: 17

  Composition:

  17 protons, 20 neutrons

  Atomic Mass: 37

• D.

  Atomic Number: 17

  Composition:

  17 protons, 37 neutrons

  Atomic Mass: 37

Answer explanation

Isotopes are members of a family of an element that all have the same number of protons but different numbers of neutrons.

Chlorine has 17 (atomic no.) protons and atomic mass of 35 amu. (18 neutrons)

Chlorine -37 (isotope)

17 protons

37 atomic mass (20 neutrons)

9. An element has X has two isotopes which may be represented as ²³⁸X and ²³⁵ X.

How does ²³⁸X differ from ²³⁵ X?

• A. ²³⁸X has 3 more protons and 3 more neutrons.

• B. ²³⁸X has 3 more electrons and 3 more neutrons.

• C. ²³⁸X has 3 more neutrons and the same number of electron

• D. ²³⁸X has 3 more protons and same number of electrons.

10.The table shows the numbers of neutrons, protons and electrons in four atoms A, B, C and D.

Which atom has become an ion?

• A.

• B.

• C.

• D.

Answer explanation

Ions are charged substances that have formed through the gain or loss of electrons.

Uneven number of proton or electron indicates ionization.

(+) cation - having extra proton

(-) anion - having extra electron