chemical calculations, Apuntes de Química

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CHEMYCAL

CALCULATIONS

Unit 5.

https://youtu.be/SfpUxcApJ0k?si=miQzDR8li7dgpgPw

E Atomic Mass of an Element » The relative atomic mass of-an element is the mass of an atom of that olement compareted to the mass of the carbon-12 atorn Carbon-12 = Anatomic mass unit is 1/12 the-mass of the:C-12 atom. 12 amu Ex: The relative mass of a hydrogen atom (1 amu) is 1/12 the* OLE mass of a C-12 atom. mass unit AS The relative atomic mass of an element ¡s defined as the weig hted average mass A a of the atomic masses of its isotopes, according to their abundance in nature Relative atomic mass = % isotope 1 Y isotope 2 Y isotope3 sad A 100 Poo Poo Ma? 1112 0f 12 amu — e = 1 amu Ms . a > o a MN . , —4 My PA LA A rá: atomic mass1 Ma: atomic mass 2 Ma: atomic mass 3 — My: atomic mass 3 »%isotopel, ve isotope 2.., my, m,, My. (atomic masses of the isotopes) e M+, Mz, My... (atomic masses of the isotopos) PERCENT COMPOSITION OF A COMPOUND The percent composition is the fixed proportion between the atoms of ¡ts elements, revealing the proportion of a compound's total mass contributed by each element. It is calculated by dividing the total mass of an element by the compound's molar mass and multiplying by 100%. Key Formula: Total mass of element | = x 100% Molar mass of compound ' Steps to Calculate Percent Composition: a O Find the Molar Mass: 7 Calculate Total Mass of Each Element: Determine the molar mass (M1) Multiply be atomic mass ofeach HO FO. a of the entire compound element by the number of atoms by summing the masses I hal ofthat element in the formula, of all atoms in the formula. (663) o Divide and Multiply: Conwert to Percentag l mans | 3-GUUa 2 Check: Divide the total mass of Multiply the result by The sum of the percent each elernent by the ms 100% to get the compositions of all elements El compound's total 100% in a compound should equal PAN molar mass. a ES 5] Wo 57 % Composition of elements = 100% https: //youtu.be/SfpUxcApJOk?si=miOzZDR8li7dgpgPw THE MOLE A mole is a large number used to measure the amount of substance. Just like we use "dozen” to refer to 12, we use “mole” to refer to 6.022 x 10% particles, 1 mole (1mol) = 6.022x10* particles (Avogadro's number) 2 pu 1 mol of carbon = 1 mol of water = 1 mol of water = 6.022 10% particdles 6.022x10% particles 6.022x10% water molecules (Avogadro's number] => ¿a a (c) 4 o n mol x 6.022-1023 particles/mol = number of particles. To calculate the number of particles in a sample, multiply the amount of substance in moles by Avogadro's number.