3.1.2 Calculating relative formula masses

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Molly

Cards (41)

Where can you find the atomic masses of elements?
On the periodic table
What is the first step to find the formula mass?
Identify the elements and their atomic masses
How would you calculate the formula mass of water (H₂O)?
Sum atomic masses of 2 H and 1 O
What components contribute to the formula mass of a compound?
All atoms present in the chemical formula
How many oxygen atoms are in the formula H₂O?
1 oxygen atom
What do chemical formulas represent?
They show how many of each element are in a molecule
How do you calculate the weighted atomic mass for water (H₂O)?
For Hydrogen:
Atomic mass: 1.008 amu
Number of atoms: 2
Calculation: $2 \times 1.008 =$ $2.016 \text{ amu}$
For Oxygen:
Atomic mass: 15.999 amu
Number of atoms: 1
Calculation: $1 \times 15.999 =$ $15.999 \text{ amu}$
What does multiplying the number of atoms by their atomic masses provide?
The weighted contribution to total formula mass
What are elements in chemistry?
Elements are the simplest substances that make up compounds
What is formula mass?
Total mass of all atoms in a formula
Why do we use grams per mole (g/mol) for RFM?
To express mass relative to the number of moles
What are the units for formula mass and atomic mass?
Formula Mass: Atomic mass units (amu)
Atomic Mass: Atomic mass units (amu)
What is the chemical symbol for hydrogen?
H
How does formula mass differ from atomic mass?
Formula mass applies to molecules, not atoms
What is the calculated atomic mass of Hydrogen in water (H₂O)?
$2.016 \text{ amu}$
What is the relative formula mass (RFM)?
Total mass of all atoms in a molecule
What is the atomic mass of Oxygen in amu?
15.999 amu
How is each element represented?
By a chemical symbol
What are the atomic masses of some common elements?
Hydrogen (H): 1.008 amu
Carbon (C): 12.011 amu
Oxygen (O): 15.999 amu
Sodium (Na): 22.990 amu
Chlorine (Cl): 35.453 amu
What is the calculated atomic mass of Oxygen in water (H₂O)?
$15.999 \text{ amu}$
What are the steps to calculate atomic mass for elements in a compound?
Identify the number of atoms for each element.
Find the atomic mass of each element.
Multiply the number of atoms by the atomic mass.
Sum the contributions for total formula mass.
What is the first step to calculate the weighted atomic mass of an element?
Multiply the atomic mass by the number of atoms
What is the first step to calculate atomic mass in a compound?
Multiply the number of atoms by atomic masses
What is the chemical symbol for oxygen?
O
What is the purpose of counting atoms in a chemical formula?
To find the formula mass
What is the atom count for each element in H₂O?
Hydrogen: 2 atoms
Oxygen: 1 atom
What is the atomic mass of Hydrogen in amu?
1.008 amu
What does multiplying the atomic mass by the number of atoms yield?
The weighted atomic mass of each element
What units are often used for RFM when dealing with large quantities?
Grams per mole (g/mol)
How many hydrogen atoms are in the formula H₂O?
2 hydrogen atoms
Why should you consult the periodic table for atomic masses?
For the most accurate atomic masses
How many atoms of Oxygen are in water (H₂O)?
1
How many atoms of Hydrogen are in water (H₂O)?
2
What does RFM stand for in chemistry?
Relative Formula Mass
How do you calculate the total mass of water (H₂O)?
Add the weighted masses of hydrogen and oxygen
What is the first step to find the total mass of a molecule?
Add the weighted atomic masses
What is the difference between relative formula mass and formula mass?
Relative Formula Mass (RFM):
Total mass expressed without units
Formula Mass:
Total mass measured in atomic mass units (amu)
If the formula mass of water (H₂O) is 17.015 amu, what is its relative formula mass?
17.015 g/mol
What is the total mass of water in atomic mass units (amu)?
17.015 amu
What do subscripts next to element symbols indicate?
The number of atoms of that element