Question

law of conservation of mass
name
in chemical changes, no
matter how big the bang, mass
is neither gained nor lost.

1. calculate the mass of the product of 6.40 g of magnesium with

1.32 g of oxygen.

1. calculate the mass of the zinc that reacts with 4.11 g of

hydrochloric acid to form 9.1 g of zinc chloride and 3.97 g of hydrogen
gas.
zinc + hydrochloric acid → zinc chloride + hydrogen

1. during the combustion of 5.00 g of butane in the presence of oxygen, 4.01 g of carbon dioxide and

3.55 g of water is given off. how much oxygen was needed to totally combust the butane?
butane + oxygen → carbon dioxide + water
more assessment questions

1. consider the following decomposition reaction: 2 h₂o₂ → 2 h₂o + o₂

if 72 grams of water (h₂o) and 64 grams of oxygen (o₂) are produced, what mass of h₂o₂ decomposed?
a. 72 grams
c. 64 grams
b. 136 grams
d. not enough information given

1. consider the following chemical reaction: 2 nacl + ca(oh)₂ → cacl₂ + 2 naoh

if the mass of 191 grams nacl reacted with 74 grams of calcium hydroxide (ca(oh)₂) and 80 grams of
sodium hydroxide (naoh) is produced, what mass of calcium chloride (cacl₂) is produced?
a. 52.5 grams
c. 91 grams
b. 111 grams
d. 185 gram
continuing law of conservation of mass

1. when 72.9g of magnesium is reacted with 28.0 g of nitrogen gas, no magnesium or nitrogen are left over.

how much magnesium nitride is produced?
magnesium + nitrogen → magnesium nitride

Explanation:

Step1: Apply the Law of Conservation of Mass

The Law of Conservation of Mass states that in a chemical reaction, the total mass of reactants equals the total mass of products.

Step2: Calculate the mass of the product for question 1

For the reaction of magnesium (\(Mg\)) and oxygen (\(O_2\)): \(2Mg + O_2
ightarrow2MgO\). The mass of the product (magnesium oxide, \(MgO\)) is the sum of the masses of magnesium and oxygen that react. So, \(m = 6.40\ g+1.32\ g\).

Step3: Calculate the mass of zinc for question 2

According to the reaction \(Zn + 2HCl
ightarrow ZnCl_2 + H_2\). Using the Law of Conservation of Mass, \(m_{Zn}=m_{ZnCl_2}+m_{H_2}-m_{HCl}\). Substitute \(m_{ZnCl_2} = 9.1\ g\), \(m_{H_2}=3.97\ g\) and \(m_{HCl} = 4.11\ g\) into the formula.

Step4: Calculate the mass of oxygen for question 3

For the reaction \(C_4H_{10}+O_2
ightarrow CO_2 + H_2O\). By the Law of Conservation of Mass, \(m_{O_2}=m_{CO_2}+m_{H_2O}-m_{C_4H_{10}}\). Substitute \(m_{C_4H_{10}} = 5.00\ g\), \(m_{CO_2}=4.01\ g\) and \(m_{H_2O}=3.55\ g\) into the formula.

Step5: Solve question 4

For the reaction \(2H_2O_2
ightarrow2H_2O + O_2\). Using the Law of Conservation of Mass, \(m_{H_2O_2}=m_{H_2O}+m_{O_2}\). Substitute \(m_{H_2O} = 72\ g\) and \(m_{O_2}=64\ g\) into the formula: \(m_{H_2O_2}=72\ g + 64\ g=136\ g\).

Step6: Solve question 5

For the reaction \(2NaCl+Ca(OH)_2
ightarrow CaCl_2 + 2NaOH\). By the Law of Conservation of Mass, \(m_{CaCl_2}=m_{NaCl}+m_{Ca(OH)_2}-m_{NaOH}\). Substitute \(m_{NaCl} = 191\ g\), \(m_{Ca(OH)_2}=74\ g\) and \(m_{NaOH}=80\ g\) into the formula: \(m_{CaCl_2}=191\ g+74\ g - 80\ g=185\ g\).

Step7: Solve question 6

For the reaction \(3Mg+N_2
ightarrow Mg_3N_2\). Using the Law of Conservation of Mass, \(m_{Mg_3N_2}=m_{Mg}+m_{N_2}\). Substitute \(m_{Mg}=72.9\ g\) and \(m_{N_2}=28.0\ g\) into the formula: \(m_{Mg_3N_2}=72.9\ g+28.0\ g = 100.9\ g\).

Answer:

1. \(7.72\ g\)
2. \(8.96\ g\)
3. \(2.56\ g\)
4. \(b\)
5. \(d\)
6. \(100.9\ g\)