MASSA MOLEKUL RELATIF ( Mr ) : KIMIA SMA KELAS 10

Summary

In this video, the process of determining relative molecular mass (Mr) is discussed. The video explains that molecules are formed by different elements and can be categorized as either elemental molecules (like O2 and H2) or compound molecules (like H2O and HCl). It details how to calculate the molecular mass by summing the relative atomic masses of the constituent atoms. Through examples such as H2, O2, CO2, H2SO4, CH3COOH, and NH4CO3, the script demonstrates how to calculate Mr for each molecule. The video emphasizes the importance of understanding molecular structure for accurate mass calculations.

Takeaways

• 😀 The script explains how to determine the relative atomic mass (Ar) of an atom and the molecular mass (Mr) of a molecule.
• 😀 Molecules can be classified into two types: elemental molecules (formed from identical atoms) and compound molecules (formed from different atoms).
• 😀 Examples of elemental molecules include O2 (oxygen) and H2 (hydrogen), while compound molecules include H2O (water) and HCl (hydrochloric acid).
• 😀 The molecular mass (Mr) is defined as the ratio of the mass of a molecule to 1/12th of the mass of a carbon-12 atom.
• 😀 Mr can be calculated by summing the relative atomic masses (Ar) of all the atoms that make up the molecule.
• 😀 For H2, the molecular mass is 2, as it is composed of two hydrogen atoms, each with an Ar of 1.
• 😀 For O2, the molecular mass is 32, since it consists of two oxygen atoms, each with an Ar of 16.
• 😀 For CO2, the molecular mass is 44, calculated by adding 12 (for carbon) and 32 (for two oxygen atoms).
• 😀 For H2SO4 (sulfuric acid), the molecular mass is 98, calculated using the atomic masses of hydrogen, sulfur, and oxygen.
• 😀 CH3COOH (acetic acid) has a molecular mass of 60, calculated using the atomic masses of carbon, hydrogen, and oxygen.
• 😀 For (NH4)2CO3 (ammonium carbonate), the molecular mass is 96, calculated by adding the atomic masses of nitrogen, hydrogen, carbon, and oxygen.

Q & A

What is the main topic discussed in the video?

The video explains how to determine the relative molecular mass (Mr) of molecules, including both elemental and compound molecules.

How is relative molecular mass (Mr) defined?

Relative molecular mass (Mr) is the ratio of the mass of one molecule of a substance to 1/12th of the mass of a carbon-12 atom.

What are the two types of molecules mentioned in the video?

The two types of molecules discussed are elemental molecules (molecules made from the same type of atoms) and compound molecules (molecules made from different types of atoms).

Can you give an example of an elemental molecule and a compound molecule?

An example of an elemental molecule is O2 (oxygen molecule, made of two oxygen atoms), while a compound molecule example is H2O (water, made of hydrogen and oxygen atoms).

How is the relative molecular mass of a molecule calculated?

The relative molecular mass is calculated by summing the relative atomic masses of all the atoms that make up the molecule.

What is the relative molecular mass of H2?

The relative molecular mass of H2 is 2, as it consists of two hydrogen atoms, each with a relative atomic mass of 1.

What is the relative molecular mass of O2?

The relative molecular mass of O2 is 32, since it consists of two oxygen atoms, each with a relative atomic mass of 16.

What is the relative molecular mass of CO2?

The relative molecular mass of CO2 is 44, calculated as (1 × 12 for carbon) + (2 × 16 for oxygen).

How is the relative molecular mass of H2SO4 calculated?

The relative molecular mass of H2SO4 is 98, calculated by adding (2 × 1 for hydrogen), (1 × 32 for sulfur), and (4 × 16 for oxygen).

What is the relative molecular mass of CH3COOH?

The relative molecular mass of CH3COOH (acetic acid) is 60, calculated by adding (2 × 12 for carbon), (4 × 1 for hydrogen), and (2 × 16 for oxygen).