ChemiCo Sample Questions for Secondary Junior

Welcome to your ChemiCo Sample Questions for Secondary Junior

1. Untreated car exhaust waste can contain pollutants such as toxic carbon monoxide gas, cancerous hydrocarbons, and nitrogen oxides which cause smog. In order to address this problem, most cars have catalytic converters installed which convert carbon monoxide into carbon dioxide, hydrocarbons into carbon dioxide and water, and nitrogen oxides to nitrogen gas and oxygen gas.

A sample of car exhaust was analysed before and after a catalytic converter was installed to
process the exhaust gas.
The concentration of which of the following gases will have decreased in the exhaust after the
catalytic converter is installed?Deselect Answer

A. CO B. CO2 C. H2O D. N2 None

1 out of 5

2. A fire is a terrible destructive event, but what is even more damaging is the automatic water irrigation systems. Museum exhibits or electronics in a hardware store will suffer from water even if they are not burned by fire, so a different fire extinguishing system is used in such places:

1) People leave the room
2) The room is completely sealed off by the system
3) Pumps fill the room with argon and thereby reduce the concentration of oxygen in the room
below the minimal 15% required to sustain burning.

Imagine a fire started in an art hall with a width of 10 m, a length of 15 m, and a height of 4 m. The
initial concentration of oxygen in the air is 20%. The fire extinguishing system pumps 100 m3 of
argon every minute. The oxygen consumption and carbon dioxide production are insignificant,
assuming the fire is detected and stopped right away

In how many minutes will the system eliminate the fire in this room?Deselect Answer

A. 4 B. 8 C. 6 D. 2 None

2 out of 5

3. Relative atomic mass of any element is based on the mass of its atoms. In the periodic table

Deselect Answer

A. 4 amu B. 37 amu C. 50 amu D. 61 amu None

3 out of 5

4. VSEPR theory is a theory of repulsion that describes the geometry of the molecule. According to that theory, molecules take a shape, which has the minimum repulsion between outer shell electrons (bonds). In other words, the bonds try to be as far away from each other as geometrically possible.

In VSEPR, single and double bonds are considered equivalent in terms of repulsions.
For the cysteine molecule below

What are approximate bond angles x and y?Deselect Answer

A. x = 90°; y = 90°

B. x = 120°; y = 109°

C. x = 120°; y = 90°

D. x = 90°; y = 109°

None

4 out of 5

5. Nixtamalization refers to the process of treating maize before it is ground into flour, in order to remove mycotoxins and to increase the nutritional value of the maize. In nixtamalization, maize is cooked and soaked in an alkaline (basic) solution.

In the Americas, where maize has been a staple food for thousands of years, nixtamalization can be
traditionally conducted as such: A special type of rock is heated to high temperatures, before being
added to water. Maize is soaked and boiled in this water, before it is ground into flour.

What could be the main constituent of this special rock?Deselect Answer

None

5 out of 5

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