Question

1- If I want to find the number of atoms in 10.0 g of S, which calculation do I perform?

2- The density of water in the Dead Sea is 1.24 g/cm3. A student obtains a 3.40 ounce sample of Dead Sea water. What is the mass of this sample in kg?

3- Which of the following statements is FALSE?

a- Metals tend to form positive ions

b- Non-metals tend to gain electrons from metals. The non-metal will then become an anion; the metal will then become a cation.

c- Ions can be formed from atoms gaining or losing electron(s)

d- Ions are forms by changing the number of neutrons in the nucleus of an atom

e- An ion has a positive or negative charge

Answer 1

1. Mass of S = 10.0g

Molar mass of S =32.1g/mol

Thus, moles of S = Mass/ Molar mass = 10.0 g/ (32.1g/mol) = 0.311 mol

1 mol contains 6.022* 10²³ atoms

THus, 0.311 mol contains 0.311* 6.022* 10²³ = 1.88*10²³ atoms

2. Density = 1.24 g/cm³

Volume = 3.40 ounce

1 ounce = 29.5735 cm³

THus, 3.40 ounce = 100.55cm³

Now, Density = mass/ Volume

Mass = density * VOlume = 1.24g/cm³ * 100.55cm³ = 126.68 g

3. Metals are electropositive in nature and hence can loose electron

Non-metals are electronegative in nature and thus tend to gain electrons to complete its octet

By loosing electrons, Metals gain positive charge and become ion and non-metals by gaining electrons gain negative charge and become ion

Thus, ion has a positive or negative charge

But ions are formed only by loosing or gaining electrons. Nucleus does not participate in reaction

Hence false statement is:

IOns are forms by changing the number of neutronns in the nucleus of an atom.