Elements and compounds (simple ver.)

What is the name of this compound? (NO3)

• Nitrate

• Ammonia

• Sulfuric acid

• Nitrogen dioxide

Answer explanation

The compound NO3 is known as nitrate. It is the ion formed from nitric acid and is commonly found in fertilizers. The other options do not correspond to the chemical formula NO3.

What happens when iron reacts with oxygen?

• It forms iron dioxide

• it forms rust

• it forms iron monoxide

• it forms iron tertoxide

Answer explanation

When iron reacts with oxygen, it primarily forms rust, which is a mixture of iron oxides, mainly iron(III) oxide (Fe2O3) and water. This process is known as oxidation and is commonly observed as the reddish-brown coating on iron.

What is the common name for sodium chloride?

• Vinegar

• Bleach

• Salt

• Baking soda

Answer explanation

The common name for sodium chloride is "salt." It is widely used in cooking and food preservation, distinguishing it from other substances like vinegar, bleach, and baking soda.

Select the most reactive metal from the list:

• Sodium

• Potassium

• Lithium

• Aluminum

Answer explanation

Lithium is the most reactive metal among the choices. It reacts vigorously with water and air, more so than sodium and potassium, making it the most reactive in this list.

Select the most electronegative element from the list:

• Sulfur

• Chlorine

• Oxygen

• Fluorine

Answer explanation

Fluorine is the most electronegative element, with an electronegativity value of 3.98 on the Pauling scale, making it more electronegative than sulfur, chlorine, and oxygen.

Which gases are the LEAST reactive in the list?

• Helium

• Hydrogen

• Nitrogen

Answer explanation

Helium is a noble gas, known for its lack of reactivity due to a full outer electron shell. In contrast, hydrogen and nitrogen can form compounds, making helium the least reactive gas in the list.

What is the name of this compound? (O2F2)

• Dioxygen difluoride

• Two oxygen, two fluoride

• Fluorine and oxygen legendary duo

• Fluorine dioxide

Answer explanation

The compound O2F2 is named based on the number of each type of atom present. 'Dioxygen' indicates two oxygen atoms, and 'difluoride' indicates two fluoride atoms, making 'Dioxygen difluoride' the correct name.

Krypton is more reactive than nitrogen

• True

• False

Answer explanation

Krypton is a noble gas and is generally unreactive, while nitrogen is more reactive due to its ability to form various compounds. Therefore, the statement that krypton is more reactive than nitrogen is false.

Balance the following equation:

---H2 + ---O2 → ---H2O

• 2,1,2

• 3,8,2

• 4,2,1

• 3,1,2

Answer explanation

To balance the equation H2 + O2 → H2O, we need 2 H2 molecules for every O2 molecule, resulting in 2 H2O. Thus, the coefficients are 2 for H2, 1 for O2, and 2 for H2O, making the correct choice 2,1,2.

Select the symbol that represents the element: Gold

• G

• Ag

• Se

• Au

Answer explanation

The symbol for Gold is 'Au', derived from its Latin name 'Aurum'. The other options, 'G', 'Ag' (Silver), and 'Se' (Selenium), do not represent Gold.