Question

1. In the reaction C5H8 + ______ O2 --> 8H2O + 5CO2, what coefficient should be placed in front of O2 to balance the reaction?
a. 5
b. 8
c. 9
d. no coefficient is needed

2. How does the law of conservation of mass apply to this reaction: C2H4 + O2 --> 2H2O + 2CO2?

a. Each element needs to be balanced.
b. The equation needs to be balanced. There are fewer oxygen atons in the equation than hydrogen or carbon.
c. Only the oxygen needs to be balanced. There are equal numbers of hydrogen and carbon.
d. The law of conservation of mass has already been applied. There is an equal number of each element on both sides of the equation

3. How does the law of conservation of mass apply to this reaction: Mg + HCl --> H2 + MgCl2?

a. The law of conservation of mass has already been applied. There is an equal number of each element on both sides of the equation.
b. Only the hydrogen needs to be balanced. There are equal amount of magnesium and chlorine.
c. Hydrogen and chlorine need to be balanced. There is an equal amount of magnesium on each side.
d. The equation needs to be balanced. There are a few hydrogen atoms in the equation than magnesium or chlorine.

4. Which of these is an example of a solution?

a. oil and vinegar in a salad dressing jar
b. a glass of water with ice in it
c. sugar stirred in tea
d. sand stirred in water

Answer 1

Answer:

For 1: The correct answer is Option c.

For 2: The correct answer is option c.

For 3: The correct answer is option c.

For 4: The correct answer is option c.

Explanation:

For 1:

For a given chemical reaction,

$C_5H_8+nO_2\rightarrow 8H_2O+5CO_2$

Number of oxygen atoms should be equal on both the sides of the reaction.

On reactant side:

Number of oxygen atoms = 2n

On product side:

Number of oxygen atoms = 18

As per the equation,

$2n=18\\\\n=9$

As, oxygen atoms should be same on both the sides, so 'n' should be equal to 9.

Hence, The correct option is Option c.

For 2:

Law of conservation of mass states that the total mass on the reactant side is equal to the total mass on the product side. This is achieved by balancing the number of atoms on both the sides.

For the given chemical equation:

$C_2H_4+nO_2\rightarrow 2H_2O+2CO_2$

On reactant side:

Number of carbon atoms = 2

Number of hydrogen atoms = 4

Number of oxygen atoms = 2n

On product side:

Number of carbon atoms = 2

Number of hydrogen atoms = 4

Number of oxygen atoms = 6

As, carbon and hydrogen atoms are equal on both the sides, so only oxygen atoms need to be balanced.

Hence, the correct answer is option c.

For 3:

Law of conservation of mass states that the total mass on the reactant side is equal to the total mass on the product side. This is achieved by balancing the number of atoms on both the sides.

For the given chemical equation:

$Mg+nHCl\rightarrow H_2+MgCl_2$

On reactant side:

Number of Magnesium atoms = 1

Number of Hydrogen atoms = n

Number of Chlorine atoms = n

On product side:

Number of Magnesium atoms = 1

Number of Hydrogen atoms = 2

Number of Chlorine atoms = 2

As, Magnesium atoms are equal on both the sides, so Hydrogen and chlorine atoms need to be balanced.

Hence, the correct answer is option c.

For 4:

A solution consists of a solute( minor component) and a solvent(major component). These two substances are different compounds. A solution is formed when solute gets completely dissolved in solvent.

For the given options:

Option a: Oil and vinegar do not mix and hence, will not form a solution.

Option b: In this ice and water are two phases of same compound, that is $H_2O$ So, this is not considered as a solution.

Option c: Sugar gets completely dissolved in tea. hence, it is a solution.

Option d: Sand and water do not mix and hence, not form a solution.

Therefore, the correct answer is option c.

Answer 2

1) Answer is: c. 9.

Balanced chemical reaction: C₅H₈ + 9O₂ → 8H₂O + 5CO₂.

Accordin to law of conservation of mass, there are eighteen oxygen atoms on both side of balanced chemical reaction.

This is example of combustion.

Combustion is reaction with oxygen.

Organic compound reacts with oxygen and produce carbon dioxide and water.

2) Answer is: c. Only the oxygen needs to be balanced. There are equal numbers of hydrogen and carbon.

According to principle of mass conservation, number of atoms must be equal on both side of chemical reaction.  

There are two oxygen atoms on the left and six oxygen atoms on the right side of chemical reaction so chemical reaction is not balanced.

Balanced reaction of ethane combustion: C₂H₄ + 3O₂ → 2H₂O + 2CO₂.

3) Answer is: Hydrogen and chlorine need to be balanced. There is an equal amount of magnesium on each side.

According to principle of mass conservation, number of atoms must be equal on both side of chemical reaction.  

There is one hydrogen atom on the left and two hydrogen atoms on the right side of chemical reaction so chemical reaction is not balanced.

There is one chlorine atom on the left and two chlorine atoms on the right side of chemical reaction so chemical reaction is not balanced.

Balanced reaction of ethane combustion: Mg + 2HCl → H₂ + MgCl₂.

4) Answer is: c. sugar stirred in tea.  

Solution is homogeneous mixture has the same proporties of its components throughout any given sample, composed of two or more substances.

Solution has a uniform composition and is able to be separated by physical means.

In aqueous solution, solvent is water and solute (in this example sugar) is a substance dissolved in water.

Other examples are heterogeneous mixture.

Heterogeneous mixture is not uniform in composition.