Compounds Vs Elements
Which of these is an element?
A. H₂O
B. NaCl
C. O₂
D. CO₂
C. O₂
A student writes the equation below:
H2+O2→2HO
Mass of reactants: 2 g of hydrogen + 16 g of oxygen = 18 g
Mass of products: 18 g of Hydroxide
Does this equation follow the law of conservation of mass?
A. Yes, the mass is equal.
B. No, the reactants have more mass.
C. No, the products have more mass.
D. No, mass was created.
A. Yes, the mass is equal.
A student balances the reaction below:
2H2+O2→2H2O
If the mass of hydrogen is 8 g and the mass of oxygen is 32 g, what is the mass of water produced?
40g
This word means the substances you start with in a chemical reaction.
Reactants
How many atoms are in H₂?
2
Which of the following is a compound?
A. N₂
B. Fe
C. H₂O
D. O₃
C. H₂O
Consider this reaction:
C+O2→CO2
Mass of reactants: 12 g carbon + 32 g oxygen = 44 g
Mass of products: 44 g carbon dioxide
Does this reaction follow the law of conservation of mass?
A. Yes, the mass is conserved.
B. No, the reactants lost mass.
C. No, the products lost mass.
D. No, oxygen was destroyed.
A. Yes, the mass is conserved.
In the reaction below,
C+O2→CO2
If the mass of carbon is 12 g and the mass of oxygen is 32 g, what is the mass of carbon dioxide?
44g
This word means the substances formed after a chemical reaction takes place.
Products
Identify and Count the atoms H₂O.
H is the chemical symbol for Hydrogen there are 2 atoms
O is the chemical symbol for Oxygen there is 1 atom
A student looks at the formula CO₂. Why is it a compound?
A. It contains only one kind of atom.
B. It has more than one type of atom chemically bonded.
C. It can be broken down by physical means.
D. It has the same number of protons and electrons.
B. It has more than one type of atom chemically bonded.
A student looks at this reaction:
Zn+S→ZnS
Mass of reactants: 65 g zinc + 32 g sulfur = 97 g
Mass of products: 90 g zinc sulfide
Does this follow the law of conservation of mass?
A. Yes, the mass is balanced.
B. No, the reactants have more mass.
C. No, the products have more mass.
D. No, sulfur disappeared.
B. No, the reactants have more mass.
In the equation below,
2Na+Cl2→2NaCl
If 46 g of sodium reacts with chlorine to form 117 g of sodium chloride, what is the mass of chlorine?
71g
The arrow in a chemical equation stands for this word, meaning “produces” or “makes.”
Yield
How many atoms are in 3CO₂?
There are 3 Carbon Atoms and 6 Oxygen Atoms.
Which example is an element and a molecule?
A. H₂
B. NaCl
C. CO
D. H₂O
A. H₂
In the equation below,
2Na+Cl2→2NaCl
Mass of reactants: 46 g sodium + 71 g chlorine = 117 g
Mass of products: 120 g sodium chloride
Does this reaction follow the law of conservation of mass?
A. Yes, both sides are equal.
B. No, the reactants have more mass.
C. No, the products have more mass.
D. No, sodium disappeared.
C. No, the products have more mass.
A student balances this equation:
Fe+S→FeS
If the mass of iron is 56 g and the mass of iron sulfide is 88 g, what is the mass of sulfur?
32g
A model that shows reactants turning into products with symbols and formulas is called this.
Chemical Equation
How many atoms are in CaCl₂?
There are a total of 3 atoms (1 calcium, 2 chlorine).
A student compares Fe and H₂O. Which statement is correct?
A. Fe is a compound, and H₂O is an element.
B. Both are compounds because they have more than one atom.
C. Fe is an element, and H₂O is a compound.
D. Both are elements because they are made of atoms.
C. Fe is an element, and H₂O is a compound.
In the reaction:
2Mg+O2→2MgO
Mass of reactants: 48 g magnesium + 32 g oxygen = 80 g
Mass of products: 80 g magnesium oxide
Does this reaction follow the law of conservation of mass?
A. Yes, both sides are equal.
B. No, the reactants weigh less.
C. No, the products weigh less.
D. No, magnesium was destroyed.
A. Yes, both sides are equal.
In the reaction,
2Mg+O2→2MgO
A student starts with 48 g of magnesium. After the reaction, the total mass of magnesium oxide is 80 g. What was the mass of oxygen?
32g
This law says that matter cannot be created or destroyed during a chemical reaction.
Law of Conservation of Mass
How many atoms are in Al₂(SO₄)₃
There are 2 Aluminum, 3 Sulfur, and 12 Oxygen atoms. A total of 17 atoms.