Question

Question
1
Question
2
Question
3
A)
Which statement describes the quantities that can be found using the number of moles?
(1 point)
It can be used to find the number of molecules or atoms, but not ions.
It can be used to find the number of molecules, atoms, or ions.
It can be used to find the number of molecules, but not atoms or ions.
It can be used to find the number of molecules or ions, but not atoms.
A)
A scientist uses 3 g of water (H
O) in an experiment. Which option describes the first step incalculating the number of molecules in 3 g of water?
(1 point)
2
Identify the molar masses of H and O.
Calculate the number of moles of water.
Apply Avogadro's number,
.
6.022
×
10
23
Determine the molar mass of water.
A)
The molar mass of ammonia (NH
) is 17.03 g/mol. Which expression correctly shows how todetermine the number of moles of ammonia equivalent to 5 g?
(1 point)
3
5
g
×
17.03
g
1
mol
5
g
×
1
g
17.03
mol
5
g
×
1
mol
17.03
g
5
g
×
17.03
mol
1
g
Question
4
Question
5
A)
How many molecules of carbon dioxide (CO
) are there in 0.450 mol of carbon dioxide?
(1 point)
2
5.42
×
10
23
2.71
×
10
23
6.02
×
10
23
1.34
×
10
24
A)
When magnesium chloride (MgCl
) is dissolved in water, which statement must be true?
(1 point)
2
The sum of the number of moles of the Mg
ions and the number of moles of the Cl
–
ions must be equalto the number of moles of MgCl
2
.
2+
The sum of the mass of the Mg
ions and the mass of the Cl
–
ions must be equal to the mass of MgCl
2
.
2+
The number of moles of the Mg
ions and the number of moles of the Cl
–
ions must each be equal to thenumber of moles of MgCl
2
.
2+
The mass of the Mg
ions and the mass of the Cl
–
ions must each be equal to the mass of MgCl
2
.
2+

Answer 1

Here are the answers (with brief explanations):

1) It can be used to find the number of molecules, atoms, or ions.
- Moles give the number of entities via Avogadro’s number.

2) Determine the molar mass of water.
- You need the molar mass before converting grams → moles.

3) 5 g × (1 mol / 17.03 g).
- Use moles = mass ÷ molar mass.

4) 2.71 × 10^23 molecules.
- 0.450 mol × 6.022×10^23 mol^−1 = 2.71×10^23.

5) The sum of the mass of the Mg2+ ions and the mass of the Cl− ions must be equal to the mass of MgCl2.
- Mass is conserved on dissociation; mole counts follow stoichiometry (1 mol Mg2+, 2 mol Cl− per mol MgCl2).