Question 1

Question

A)Why are open systems inappropriate for studying the conservation of mass?(1 point)
Responses

Heat can escape from or enter the system.
Heat can escape from or enter the system.

Matter may be created or destroyed within the system.
Matter may be created or destroyed within the system.

The sample may become contaminated.
The sample may become contaminated.

Matter may be lost to or gained from the surroundings.
Matter may be lost to or gained from the surroundings.
Question 2
A)A student claims that the reaction of hydrogen and oxygen to form hydrogen peroxide is evidence supporting the claim that mass is conserved in a reaction. The chemical equation the student uses for the reaction is shown: H2 + O2 → H2O2
. Does this evidence support the claim? Why or why not?(1 point)
Responses

No, it does not support the claim because more oxygen is necessary.
No, it does not support the claim because more oxygen is necessary.

No, it does not support the claim because more hydrogen is necessary.
No, it does not support the claim because more hydrogen is necessary.

Yes, it supports the claim because the mass before and after is the same.
Yes, it supports the claim because the mass before and after is the same.

Yes, it supports the claim because the equation is balanced.
Yes, it supports the claim because the equation is balanced.
Question 3
A)A student records the masses of two reactants (baking soda & vinegar), and then mixes them. The reactants bubble and foam, forming a paste. The student measure the mass again, and the final mass is slightly less than the sum of the initial masses. Considering that mass is supposed to be conserved, which statement is a possible explanation for this "loss" of mass?(1 point)
Responses

There was not enough of the reactants to form as much product as possible, so some reactant was left over; this changes the final mass.
There was not enough of the reactants to form as much product as possible, so some reactant was left over; this changes the final mass.

The bubbling indicates a gas was formed, so some atoms formed gas; therefore, mass was transferred to the atmosphere.
The bubbling indicates a gas was formed, so some atoms formed gas; therefore, mass was transferred to the atmosphere.

Some of the mass was left over as remnants in the containers the student used.
Some of the mass was left over as remnants in the containers the student used.

Pastes are in between a liquid and a solid, and they have less mass than solids (i.e., baking soda).
Pastes are in between a liquid and a solid, and they have less mass than solids (i.e., baking soda).
Question 4
A)Which quantity is used to define 1 atomic mass unit (amu)?(1 point)
Responses

The mass of one neutral hydrogen atom.
The mass of one neutral hydrogen atom.

One-twelfth the mass of a neutral carbon atom.
One-twelfth the mass of a neutral carbon atom.

One-sixteenth the mass of a neutral carbon atom.
One-sixteenth the mass of a neutral carbon atom.

One-sixteenth the mass of a neutral oxygen atom.
One-sixteenth the mass of a neutral oxygen atom.
Question 5
A)
Use the equation to answer the question.

FeCl3+ 3NH4OH → Fe(OH)3 + 3NH4Cl

Which statement about the equation is correct?

(1 point)
Responses

Mass is conserved because the number of different elements in the reactants equals the number of different elements in the products.
Mass is conserved because the number of different elements in the reactants equals the number of different elements in the products.

Mass is conserved because the number of molecules in the reactants equals the number of molecules in the products.
Mass is conserved because the number of molecules in the reactants equals the number of molecules in the products.

Mass is conserved because the number of reactants equals the number of products.
Mass is conserved because the number of reactants equals the number of products.

Mass is conserved because the number of each atom in the reactants equals the number of each atom in the products.
Mass is conserved because the number of each atom in the reactants equals the number of each atom in the products.
Question 6
A)The atomic mass of Iron (Fe) is 55.85 amu, and the atomic mass of chlorine (Cl) is 35.45 amu. Which molar mass is correct for iron III chloride (FeCl3
)?(1 point)
Responses

129.59 g/mol
129.59 g/mol

162.20 g/mol
162.20 g/mol

91.30 g/mol
91.30 g/mol

126.75 g/mol
126.75 g/mol
Question 7
A)When the products of a reaction are known, which fact can always be deduced about the reactants?(1 point)
Responses

the number of reactants.
the number of reactants.

the state of the reactants.
the state of the reactants.

the mass of each reactant.
the mass of each reactant.

the number of atoms in the reactants.
the number of atoms in the reactants.
Question 8
A)
Hydrogen peroxide decomposes into water & oxygen according to the following reaction.

2H2O2 → Water + Oxygen

Based on the law of conservation of mass, which could be the product of the reaction?

(1 point)
Responses

2H2O + O2
2H2O + O2

2H2O + 2O2
2H2O + 2O2

H2O + O2
H2O + O2

4H2O + 2O2
4H2O + 2O2
Question 9
A)Calcium carbonate (CaCO3
) can undergo a chemical reaction to produce calcium oxide (CaO
) and carbon dioxide (CO2
). Which possible masses of calcium oxide and carbon dioxide can form when 200g of calcium carbonate undergoes this chemical reaction?(1 point)
Responses

40g CaO
and 12g CO2
40g cap c A cap o and 12g cap c cap o sub 2

200g CaO
and 200g CO2
200g cap c A cap o and 200g cap c cap o sub 2

56g CaO
and 44g CO2
56g cap c A cap o and 44g cap c cap o sub 2

112g CaO
and 88g CO2
112g cap c A cap o and 88g cap c cap o sub 2
Question 10
A)
Use the chemical equation to answer the question.

2HCl(ag) + Zn(s) → ZnCl2(aq) + H2(g)

The molar mass of hydrogen (H) is 1g/mol, the molar mass of chlorine (Cl) is 35g/mol, and the molar mass of zinc (Zn) is 65g/mol. When 130g of zinc react completely in hydrochloric acid (HCl), how much is the total mass of the products?

(1 point)
Responses

274g
274g

130g
130g

144g
144g

270g
270g
Question 11
A)
Propane reacts with oxygen to produce carbon dioxide and water according to the following equation:

C3H8+5O2→3CO2+4H2O

Which ratio of components is correct?

(1 point)
Responses

For every 3 moles of carbon dioxide produced, 5 moles of oxygen react.
For every 3 moles of carbon dioxide produced, 5 moles of oxygen react.

For every 4 moles of water produced, 3 moles of propane react.
For every 4 moles of water produced, 3 moles of propane react.

For each mole of oxygen that reacts, 3 moles of carbon dioxide are produced.
For each mole of oxygen that reacts, 3 moles of carbon dioxide are produced.

For each mole of propane that reacts, 5 moles of oxygen are produced.
For each mole of propane that reacts, 5 moles of oxygen are produced.
Question 12
A)
Elements A and B react according to the following equation:

4A+B2→2A2B

The molar mass of A is 12g/mol. The molar mass of B is 4g/mol. The molar mass of A2B
is 28g/mol. When the goal of the reaction is to produce 112g of the product, how many grams of reactant A should be present initially?

(1 point)
Responses

24
24

48
48

16
16

96
96
Question 13
A)The molar mass of CaCl2
is 110.98g/mol. How many molecules of CaCl2
are there in 4g?(1 point)
Responses

2.409×1024
molecules
2 point 4 0 9 times 10 to the 24th power molecules

2.170 × 1022
molecules
2.170 × 1022
molecules

2.673×1026
molecules
2 point 6 7 3 times 10 to the 26th power molecules

5.426×1021
molecules
5 point 4 2 6 times 10 to the 21th power molecules
Question 14
A)
Use the table of molar masses to complete the question. Do NOT use any other values except the ones provided in the table below.

Element Molar Mass (g/mol)
carbon 12.01
hydrogen 1.01
oxygen 16.00
Using only the molar mass values provided in the table above, correctly calculate the molar mass of Ethanol (CH3CH2OH
) and type in the value below. (Your answer should be a number with 2 decimal places; i.e. the hundredths place).

(2 points)
The molar mass of Ethanol is: $$ grams
Question 15
A)
Use the table of molar masses to complete the question. Do NOT use any other values except the ones provided in the table below.

Element Molar Mass (g/mol)
carbon 12.01
hydrogen 1.01
oxygen 16.00
A chemist will use a sample of 30g of glucose (C6H12O6
) in an experiment. Determine the number of moles of glucose the chemist will use based on the molar mass values provided in the table. (Your value should be rounded to 2 decimal places; i.e. the hundredths place).

(2 points)
The number of moles the chemist will use is: $$ moles.
Question 16
A)
Determine if the statement is True or False.

The molar mass of ammonium acetate is 77.083 g/mol. A student uses 0.100 mol of ammonium acetate in a chemical reaction. The student claims that the reaction uses (0.100 mol)(77.083 gmol) = 7.71 g
of ammonium acetate, which has (7.71)(6.022×1023) = 4.64×1024
molecules. Did the student determine the correct number of molecules of ammonium acetate used in the reaction?

(2 points)
Responses

The student calculated the correct number of molecules of ammonium acetate.
The student calculated the correct number of molecules of ammonium acetate.

The student miscalculated the number of molecules of ammonium acetate.

Answer 1

Here are the responses to your questions:

Question 1

Answer: Matter may be lost to or gained from the surroundings.

Question 2

Answer: Yes, it supports the claim because the equation is balanced.

Question 3

Answer: The bubbling indicates a gas was formed, so some atoms formed gas; therefore, mass was transferred to the atmosphere.

Question 4

Answer: One-twelfth the mass of a neutral carbon atom.

Question 5

Answer: Mass is conserved because the number of each atom in the reactants equals the number of each atom in the products.

Question 6

Answer: 162.20 g/mol

Question 7

Answer: the number of atoms in the reactants.

Question 8

Answer: 2H2O + O2

Question 9

Answer: 112g CaO and 88g CO2

Question 10

Answer: 274g

Question 11

Answer: For every 3 moles of carbon dioxide produced, 5 moles of oxygen react.

Question 12

Answer: 96

Question 13

Answer: 1.812 × 10^22 molecules (Note: The exact value may depend on calculation; hence it's prudent that you double-check by performing the mole calculation using the provided molar mass.)

Question 14

Answer: (2.46) grams (Note: You might want to perform the calculation using the provided molar masses here.)

Question 15

Answer: 0.50 moles (30 g divided by the molar mass of glucose, which is 180.18 g/mol based on the information given in the question.)

Question 16

Answer: The student miscalculated the number of molecules of ammonium acetate.

Make sure to verify the molar mass calculations and any specific numerical answers with the data given.