Question

co₂ noₓ
h₂o co
o₂ fuel

e. is the flame in the image a result of a chemical or physical change? how do you know?
f. give one example of matter from the image and one example of energy from the image:

• matter:
• energy:

g. what pure substances are in the image:

• elements:
• compounds:

h. iron and oxygen gas reacted to form fe₂o₃. how much iron reacted with 16g of oxygen gas to produce 44g of fe₂o₃?

1. choose the correct answer.

nitrogen gas (n₂) reacts with hydrogen gas (h₂) to form ammonia gas (nh₃). models of the molecules are shown.
which model correctly shows that the mass is conserved in the reaction?
diagrams of molecular models

3 • experimental design & data analysis
a. in the lab you want to determine the effect of changing temperature on the volume of a balloon. identify the independent and dependent variables and form a hypothesis.
independent variable:
dependent variable:
hypothesis:

Explanation:

Sub - question h (Iron and Oxygen reaction)

Step1: Recall the law of conservation of mass

The law of conservation of mass states that in a chemical reaction, the total mass of reactants is equal to the total mass of products. The formula is \(m_{reactants}=m_{products}\), where \(m_{reactants}\) is the sum of the masses of all reactants and \(m_{products}\) is the mass of the product.

Step2: Identify reactants and product

The reactants are iron (\(Fe\)) and oxygen gas (\(O_2\)), and the product is iron(III) oxide (\(Fe_2O_3\)). We know the mass of oxygen gas (\(m_{O_2} = 16g\)) and the mass of the product (\(m_{Fe_2O_3}=44g\)).

Step3: Calculate the mass of iron

Let the mass of iron be \(m_{Fe}\). According to the law of conservation of mass, \(m_{Fe}+m_{O_2}=m_{Fe_2O_3}\). Substituting the known values, we get \(m_{Fe}+ 16g=44g\). Solving for \(m_{Fe}\), we have \(m_{Fe}=44g - 16g = 28g\).

Sub - question 1 (Nitrogen and Hydrogen reaction - Mass Conservation)

To determine which model shows mass conservation, we use the law of conservation of mass (also related to the balanced chemical equation for the reaction \(N_2 + 3H_2\xlongequal{}2NH_3\)). The number of each type of atom should be the same on both sides of the reaction (in the reactant and product models).

• For the reaction \(N_2+3H_2 = 2NH_3\), we need 1 molecule of \(N_2\) (2 N atoms) and 3 molecules of \(H_2\) (6 H atoms) to form 2 molecules of \(NH_3\) (2 N atoms and 6 H atoms).
• Let's analyze the options:
• Option (the one with 1 \(N_2\) and 3 \(H_2\) on the left and 2 \(NH_3\) on the right) will have the same number of N and H atoms on both sides, thus showing mass conservation. Assuming the correct option is the one that has 1 \(N_2\) molecule, 3 \(H_2\) molecules as reactants and 2 \(NH_3\) molecules as products (the option with the correct stoichiometry based on the balanced equation).

Step1: Write the balanced chemical equation

The reaction between nitrogen gas (\(N_2\)) and hydrogen gas (\(H_2\)) to form ammonia (\(NH_3\)) is \(N_2 + 3H_2\xlongequal{}2NH_3\). This means 1 molecule of \(N_2\) (containing 2 N atoms) reacts with 3 molecules of \(H_2\) (containing 6 H atoms) to form 2 molecules of \(NH_3\) (containing 2 N atoms and 6 H atoms).

Step2: Analyze the models

A model that shows mass conservation must have the same number of each type of atom (N and H) on the reactant side (left) and product side (right). So we look for a model where there is 1 \(N_2\) molecule, 3 \(H_2\) molecules on the left and 2 \(NH_3\) molecules on the right. This model will have 2 N atoms and 6 H atoms on both sides, satisfying the law of conservation of mass.

Sub - question 3a (Experimental Design - Balloon Volume and Temperature)

Step1: Define Independent Variable

The independent variable is the variable that is changed or controlled in an experiment to test the effect on the dependent variable. In this experiment, we want to change the temperature of the balloon, so temperature is the independent variable.

Step2: Define Dependent Variable

The dependent variable is the variable that is being measured or observed and is affected by the independent variable. Here, we are measuring the volume of the balloon, so the volume of the balloon is the dependent variable.

Step3: Formulate Hypothesis

Based on the relationship between temperature and volume of a gas (Charles's Law for ideal gases), we can hypothesize that as the temperature (independent variable) increases, the volume (dependent variable) of the balloon (which contains a gas) will increase, assuming pressure and the amount of gas remain constant.

Answer:

28g