Question

**Instructions:** Choose 8 of the 10 problems
below. Show your work in detail. Answer the questions directly in
this template. Before doing this, it is highly recommending that
you thoroughly review the three examples in the Unit Lesson.

- Consider two stable isotopes, helium-3 and helium-4. How many neutrons and protons are there in each isotope? What are the mass numbers? Hint: Do not confuse mass number with atomic mass. Review the definition of them.

- If two protons and two neutrons are added to the nucleus of a carbon atom, what nucleus does it become? Hint: The proton number equals to the atomic number. See the periodic table of Figure 11.9 on. p. 216 in the textbook.

- Calculate the molecular mass of hydrogen sulfide,
H
_{2}S in atomic mass unit u. Use the periodic table of Figure 11.9 on. p. 216 in the textbook. Hint: The molecular mass of a molecule is the sum of the atomic masses of its atoms. For instance, hydrogen and oxygen have atomic masses of 1.0079u and 15.999u respectively (See Figure 11.9 on. page 216 in the textbook). Thus, the molecular mass of a water molecule (H_{2}O) is (2x1.0079u+15.999u=18.0148u). In order to express enormous numbers of atoms or molecules, the gram-mole, or, more simply, the mole, is used.

- Which has the greater density: 100 kg of ice or 10 kg of gold? Consult the Table 12.1 on p. 230 in the textbook. Hint: Be careful about the unit of density, mass, and volume.

- What is the volume of 1,000 kg of ice? Consult the Table 12.1 on p. 230 in the textbook. Hint: Use the relationship between density, mass, and volume. Mass=density x volume.

- How many gold atoms are in a 1 kg gold bar? The chemical symbol of gold is Au. Consult

The Periodic Table in Figure 11.9 on
p. 216 in the textbook. Hint: Remember 1u=1.66x10^{-27}kg.
1 mole= 6.022x10^{23}, which is Avogadro’s number

- There are two water containers: a cube and a sphere. The length
of the side of the cube is 3 m and the radius of the sphere is 3 m.
When the two containers are full of water, which container contains
more mass? Hint: Use the relationship between density, mass, and
volume. Mass=density x volume. If the length of the side of a cube
is r m, the volume of the cube is r
^{3}m^{3}.

If the radius of a sphere is r, the
volume of the sphere is 4/3 xπ x r^{3} m^{3}. Here
x r^{3} =r x r x r.

- A force of 100 N is required to squeeze a hand exerciser that has a coiled spring. The spring is compressed by 0.02 meters. Determine the spring constant. Hint: Use Hooke’s law. The restoring force of an ideal spring is F=-kx, where k is the spring constant and x is the displacement of the spring from its original length.

Answer #1

**You have posted so many questions at
once..............Please understand that one question at a time can
be done !!!**

___________________________________________

1)

Consider two stable isotopes, helium-3 and helium-4. How many neutrons and protons are there in each isotope? What are the mass numbers?

**Solution** -
Helium - 3 has 2 protons and 1 neutron. Mass number = 3

Helium - 4 has 2 protons and 2 neutrons . Mass number = 4

________________________________________

2)

If two protons and two neutrons are added to the nucleus of a carbon atom, what nucleus does it become?

**Solution** - for
carbon, atomic number = 6

atomic weight = proton number + neutron number = 6 + 6 = 12

so,

when we add 2 protons, atomic number = 8

when we add 2 protons and 2 neutrons, atomic weight = 16

it becomes an OXYGEN atom

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