One molecule of bromine (Br2) and two molecules of potassium chloride (KCl) combine in a reaction. How many atoms are in the products?
A. two
B. four
C. three
D. six
The reaction involves one molecule of bromine (Br2) and two molecules of potassium chloride (KCl).
Breaking down the reactants:
Br2 = 2 atoms of bromine (2 Br atoms)
KCl = 1 atom of potassium (K) + 1 atom of chlorine (Cl) = 2 atoms in total (1 K atom and 1 Cl atom)
Combining the reactants:
Br2 + 2KCl = 2KBr + Cl2
Breaking down the products:
2KBr = 2 atoms of potassium (2 K atoms) + 2 atoms of bromine (2 Br atoms)
Cl2 = 2 atoms of chlorine (2 Cl atoms)
Adding the atoms in the products:
2 K atoms + 2 Br atoms + 2 Cl atoms = 6 atoms
Therefore, there are six atoms in the products.
Answer: D. six
Use the unbalanced chemical equation to answer the question.
2NaHCO3 → Na2CO3 + CO2
Which of the following can be added to the products to balance the equation?
A. O2
B. CH2OH
C. H2O
D. H2
The unbalanced chemical equation is:
2NaHCO3 → Na2CO3 + CO2
To balance this equation, we need to ensure that there is an equal number of atoms on both sides of the equation.
Analyzing the equation, we can see that there are two sodium (Na) atoms, two hydrogen (H) atoms, two carbon (C) atoms, and six oxygen (O) atoms on the left-hand side (reactants).
On the right-hand side (products), there are two sodium (Na) atoms, one carbon (C) atom, and three oxygen (O) atoms.
To balance the equation, we need to add another carbon (C) atom and four oxygen (O) atoms to the products.
The only option that adds oxygen to the products is H2O, which consists of two hydrogen atoms (H) and one oxygen atom (O).
Therefore, the answer is:
C. H2O
Use the chemical equation to complete the activity.
2Cu+S→Cu2S
Copper (Cu) reacts with sulfur (S) to form copper sulfide as shown in the equation. A scientist adds 12.7 grams of Cu to 3.2 grams of S to start the reaction. In this reaction, all of the copper and all of the sulfur react. Before running the experiment, the scientist expected the products of the reaction will be a total of 15.9 grams of copper sulfide (Cu2S). In 1–2 sentences, explain the law that the scientist used to predict that the product of the reaction would be 15.9 grams of copper sulfide.