Cobalt has a mass number of 59 and an atomic number of 27. A student wants to create a model of a cobalt atom. Which statement about the model is correct?
The model should
O show 32 protons and 59 neutrons.
The model should
O show 59 protons and 27 neutrons.
The model should
O show 27 protons and 27 neutrons.
The model should
O show 27 protons and 32 neutrons.
The correct statement is: The model should show 27 protons and 32 neutrons.
In a molecule of lithium sulfide, there are two atoms of lithium and one atom of sulfur. Which statement about lithium sulfide is correct?
The chemical
• formula for lithium sulfide is LiS2.
A molecular model
O Of lithium sulfide
would have two spheres.
Both lithium and
• sulfur form positive
ions.
The atoms in lithium
O sulfide are held
together by bonds.
The correct statement is: The atoms in lithium sulfide are held together by bonds.
Which element has the same
number of valence electrons as
bromine (Br)?
(1 point)
• chlorine (CI)
• selenium (Se)
O potassium (K)
• krypton (Kr)
The element that has the same number of valence electrons as bromine (Br) is chlorine (CI).
You sure?
Apologies for the incorrect response. Bromine (Br) belongs to Group 17 or Group VIIA of the periodic table, which means it has 7 valence electrons. Therefore, 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)
O They have similar
atomic weights.
O They have similar
reactivity.
o They are both hard
and brittle.
o They are both
colorless.
The correct answer is: They have similar reactivity. Sodium (Na) and potassium (K) are both alkali metals and belong to Group 1 or Group IA of the periodic table. Elements in the same group tend to have similar chemical properties, including reactivity. Sodium and potassium both have one valence electron and react similarly to form ionic compounds and gain a stable electron configuration.
A student cuts some fabric into two pieces. Is this change physical or chemical? (1 point)
It is a physical
O change because
there is no reaction.
It is a chemical o change because there is no phase change.
It is a physical o change because the process is reversible.
It is a chemical
• change because the size changes.
The correct answer is: It is a physical change because there is no reaction. Cutting a fabric into two pieces does not involve a chemical reaction, but rather a change in physical appearance or size. The fabric is still made up of the same material, just in different sizes or shapes.
How are chemical changes different from physical changes?
(1 point)
They include shifts
• in the phase of matter.
• They are reversible.
O They form new
substances.
• They involve heat.
The correct answer is: They form new substances. Chemical changes involve a transformation of substances, resulting in the formation of new substances with different chemical properties. Physical changes, on the other hand, do not result in the formation of new substances and primarily involve changes in physical properties such as size, shape, or phase of matter. Not all physical changes are reversible, and not all chemical changes involve the release or absorption of heat.
How does a balanced chemical equation demonstrate the Law of Conservation of Mass? (1 point)
it shows that no o atoms have been gained or lost during the reaction
it shows that the properties of the
• elements stay the same after the reaction
it shows that only physical changes
• follow the Law of
Conservation of
Mass
it shows that all
• compounds remain bonded after the reaction
The correct answer is: it shows that no atoms have been gained or lost during the reaction. A balanced chemical equation is a representation of a chemical reaction that ensures that the number of atoms of each element is the same on both sides of the equation. This demonstrates the Law of Conservation of Mass, which states that in a chemical reaction, matter cannot be created or destroyed. The total mass of the reactants must be equal to the total mass of the products. Therefore, a balanced chemical equation shows that the number of atoms of each element is conserved and that no atoms are gained or lost during the reaction.
Is that correct?
Apologies for the confusion caused by my previous response. The correct answer is indeed: it shows that no atoms have been gained or lost during the reaction. A balanced chemical equation adheres to the Law of Conservation of Mass by ensuring that the number of atoms of each element remains the same on both sides of the equation. This demonstrates that mass is conserved in a chemical reaction, as no atoms are created or destroyed. Thank you for pointing out the error, and I apologize for any confusion.
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 -> 2NaCI
If the total mass of the reactants is 58.44 amu, what will be the total mass of the products?
(1 point)
• 116.88 amu
О 60 amu
O 29.22 amu
O 58.44 amu
The total mass of the products can be determined by adding up the individual molar masses of sodium chloride (NaCl). The molar mass of sodium (Na) is 22.99 g/mol, and the molar mass of chlorine (Cl) is 35.45 g/mol.
Since the balanced equation shows that 2 moles of sodium (2Na) react with 1 mole of chlorine (Cl2) to form 2 moles of sodium chloride (2NaCl), we can calculate the mass of 1 mole of sodium chloride as follows:
(2 mol NaCl) * (22.99 g/mol NaCl) = 45.98 g
Therefore, the total mass of the products (2 moles of sodium chloride) will be:
(2 mol NaCl) * (45.98 g/mol NaCl) = 91.96 g
Due to the number of significant figures in the question, the answer should be rounded to two decimal places:
The total mass of the products will be 91.96 amu.
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 + Cl^2 -> 2NaCI
If the total mass of the reactants is 58.44 amu, what will be the total mass of the products?
(1 point)
• 116.88 amu
О 60 amu
O 29.22 amu
O 58.44 ambage
To find the total mass of the products, we need to determine the molar mass of sodium chloride (NaCl).
The molar mass of sodium (Na) is 22.99 g/mol, and the molar mass of chlorine (Cl) is 35.45 g/mol.
From the balanced chemical equation provided, we know that 2 moles of sodium react with 1 mole of chlorine to form 2 moles of sodium chloride.
To find the total mass of the products, we can calculate the molar mass of NaCl and then multiply it by the number of moles of NaCl formed.
Molar mass of NaCl = (22.99 g/mol Na) + (35.45 g/mol Cl) = 58.44 g/mol NaCl
Total mass of the products = (2 moles NaCl) * (58.44 g/mol NaCl) = 116.88 g
Therefore, the total mass of the products will be 116.88 amu.
Which procedure could be used to demonstrate that matter is conserved during a physical change? (1 point)
Find the mass of an apple. Cut the apple o and remove the core. Find the mass of the remaining apple.
Find the mass of a o raw egg. Cook the egg. Find the mass of the cooked egg.
Find the mass of a cup of water. Boil
• the water. Find the mass of the water that remains.
Find the mass of a piece of ice. Let the
• ice melt. Find the mass of the liquid water.
The correct answer is: Find the mass of a cup of water. Boil the water. Find the mass of the water that remains.
By measuring the mass of a cup of water before and after boiling it, you can demonstrate that matter is conserved during a physical change. The boiling causes the water to change phase from a liquid to a gas, but the total mass of the water will remain the same. This experiment illustrates the Law of Conservation of Mass, which states that the mass of an isolated system remains constant, regardless of any physical or chemical changes that may occur.
One molecule of bromine (Br) and two molecules of potassium chloride (KCI) combine in a reaction. How many atoms are in the products? (1 point)
• four
• two
• three
six
To determine the number of atoms in the products, we need to examine the chemical equation that represents the reaction between one molecule of bromine (Br) and two molecules of potassium chloride (KCl):
Br2 + 2KCl → 2KBr + Cl2
From the equation, we can see that one molecule of bromine (Br2) combines with two molecules of potassium chloride (2KCl) to form two molecules of potassium bromide (2KBr) and one molecule of chlorine (Cl2).
To calculate the number of atoms, we need to multiply the number of molecules by the number of atoms present in each molecule.
In the products, 2 molecules of potassium bromide (2KBr) will have:
2 (molecules) × 1 (bromine atom in each molecule) = 2 bromine atoms
And 1 molecule of chlorine (Cl2) will have:
1 (molecule) × 2 (chlorine atoms in each molecule) = 2 chlorine atoms
Therefore, when the reaction is complete, the products will have a total of four atoms: 2 bromine atoms and 2 chlorine atoms.
The correct answer is: four.
Use the unbalanced chemical equation to answer the question.
2NaHCOz -> Na,COz + COz
Which of the following can be added to the products to balance the equation?
(1 point)
O H2
0 H,0
• CH^2OH
0 02
To balance the equation 2NaHCO3 -> Na2CO3 + CO2, we need to ensure that the same number of atoms of each element is present on both sides of the equation.
Looking at the unbalanced equation, we can see that there are 2 sodium atoms (Na) on the left side but only 1 sodium atom on the right side. To balance the sodium, we need to add a coefficient of 2 in front of Na2CO3, so it becomes 2Na2CO3.
Next, we can observe that there are 2 hydrogen (H) atoms on the left side but no hydrogen atoms on the right side. To balance the hydrogen, we need to add a coefficient of 2 in front of H2O, so it becomes 2H2O.
Now, the equation is balanced as follows:
2NaHCO3 -> 2Na2CO3 + CO2 + H2O
None of the options provided (H2, H2O, CH2OH, O2) can be added to the products to balance the equation.