Question

1- For an element, how does Avogadro’s number connect the atomic and macroscopic scales?

It describes the number of grams in 1 mole of an element.


It describes the number of atoms in 1 gram of an element.


It describes the number of atoms in 1 mole of an element.


It describes the number of moles in 1 gram of an element.



2- The atomic mass of the element platinum (Pt) is 195.08 amu. How many atoms of platinum are in 195.08 grams?


6.022×1023 atoms


1.175×1026 atoms


1.951×1025 atoms


3.087×1021 atoms



3- The atomic mass of copper (Cu) is 63.546 amu, the atomic mass of sulfur (S) is 32.065, and the atomic mass of oxygen (O) is 15.999 amu. Which molar mass is correct for copper sulfate (CuSO4)?


159.607 g/mol


225.802 g/mol


111.610 g/mol


446.440 g/mol

Answer 1

1. It describes the number of atoms in 1 mole of an element.

2. 195.08 g Pt / 195.08 g/mol = 1 mol Pt

1 mol Pt x 6.022 x 10^23 atoms/mol = 6.022 x 10^23 atoms

The correct answer is: 6.022×10^23 atoms

3. Cu: 63.546 g/mol

S: 32.065 g/mol

O (4 atoms): 4 x 15.999 g/mol = 63.996 g/mol

Molar mass of CuSO4 = 63.546 + 32.065 + 63.996 = 159.607 g/mol

The correct answer is: 159.607 g/mol