In a molecule of lithium sulfide, there are two atoms of lithium and one atom of sulfur. Which statement about lithium sulfide is correct?(1 point)
Responses
The chemical formula for lithium sulfide is LiS2.
The chemical formula for lithium sulfide is LiS 2 .
Both lithium and sulfur form positive ions.
Both lithium and sulfur form positive ions.
The atoms in lithium sulfide are held together by bonds.
The atoms in lithium sulfide are held together by bonds.
A molecular model of lithium sulfide would have two spheres.
A molecular model of lithium sulfide would have two spheres.
The correct response is "They have similar reactivity." Sodium (Na) and potassium (K) are both in Group 1 of the periodic table, also known as the alkali metals. Elements in the same group tend to have similar properties and reactivity, which is why sodium and potassium share this classification.
The statement "The atoms in lithium sulfide are held together by bonds" is correct.
Which element has the same number of valence electrons as bromine (Br)?
(1 point)
Responses
selenium (Se)
selenium (Se)
krypton (Kr)
krypton (Kr)
chlorine (Cl)
chlorine (Cl)
potassium (K)
The element that has the same number of valence electrons as bromine is chlorine (Cl).
Why are sodium (Na) and potassium (K) in the same group on the periodic table?(1 point)
Responses
They are both hard and brittle.
They are both hard and brittle.
They have similar atomic weights.
They have similar atomic weights.
They have similar reactivity.
They have similar reactivity.
They are both colorless.
They are both colorless.
How are chemical changes different from physical changes?(1 point)
Responses
They include shifts in the phase of matter.
They include shifts in the phase of matter.
They form new substances.
They form new substances.
They are reversible.
They are reversible.
They involve heat.
The correct response is "They form new substances." Chemical changes involve the formation of new substances with different chemical properties. Physical changes, on the other hand, do not produce new substances but instead involve changes in the physical state or appearance of a substance, such as changes in size, shape, or phase of matter.
The correct response is "it shows that no atoms have been gained or lost during the reaction." The Law of Conservation of Mass states that in a chemical reaction, the total mass of the reactants must equal the total mass of the products. A balanced chemical equation ensures that the number of atoms of each element is the same on both sides of the equation, demonstrating that no atoms have been gained or lost during the reaction and thus confirming the Law of Conservation of Mass.
Sodium reacts with chlorine to form the compound sodium chloride, or salt. The chemical formula below shows how the two elements combine into a compound.
2Na + Cl2 → 2NaCl
If the total mass of the reactants is 58.44 amu, what will be the total mass of the products?
(1 point)
Responses
60 amu
60 amu
58.44 amu
58.44 amu
116.88 amu
116.88 amu
29.22 amu
To determine the total mass of the products, we need to calculate the molar mass of NaCl, which is the product formed in the reaction.
The molar mass of Na is 22.99 g/mol, and the molar mass of Cl is 35.45 g/mol.
Since the balanced equation tells us that 2 moles of Na react with 1 mole of Cl2 to form 2 moles of NaCl, we can calculate the molar mass of NaCl:
Molar mass of NaCl = 2 * (molar mass of Na) + 1 * (molar mass of Cl)
= 2 * 22.99 g/mol + 35.45 g/mol
= 45.98 g/mol + 35.45 g/mol
= 81.43 g/mol
Now, to find the total mass of the products, we need to convert the molar mass of NaCl to amu:
Total mass of products = (molar mass of NaCl) * (total number of moles of NaCl)
The balanced equation tells us that 2 moles of NaCl are formed for every 2 moles of Na and 1 mole of Cl2. This means that 2 moles of NaCl are formed for every 58.44 amu (total mass of reactants).
So, the total mass of the products will be:
Total mass of products = (81.43 g/mol) * (58.44 amu / 81.43 g/mol)
= 58.44 amu
Therefore, the correct response is "58.44 amu".