Read the first worked example with the solution open so the structure is clear.
Try the practice problems before revealing each solution.
Use the related concepts and background knowledge badges if you feel stuck.
What to Focus On
Core idea:Product starts by naming reactants and products, then checks conservation with a balanced equation.
Common stuck point:Students often know a formula related to product but skip the recognition step: Am I tracking reactants, products, atom conservation, evidence of new substances, and the balanced equation? That leads to a correct-looking substitution attached to the wrong chemical model.
Sense of Study hint:Ask: Am I tracking reactants, products, atom conservation, evidence of new substances, and the balanced equation?
Worked Examples
Example 1
easy
Define the term 'product' in a chemical reaction. In the reaction Mg+2HCl→MgCl2+H2, identify all products.Identify the products in this reaction (right side of the arrow).
Answer
Products: MgCl2 and H2 (right side of the arrow)
First step
1
A product is a substance that is formed (produced) during a chemical reaction. Products appear on the right side of the chemical equation.
Full solution
2
In this reaction, the products are MgCl2 (magnesium chloride) and H2 (hydrogen gas).
3
Products have different properties from the reactants — MgCl2 is a salt dissolved in solution, and H2 is a flammable gas.
Products are the new substances created by the rearrangement of atoms during a chemical reaction. The law of conservation of mass ensures that the total mass of products equals the total mass of reactants.
Example 2
medium
In the reaction Fe2O3+3CO→2Fe+3CO2, identify the products and calculate how many moles of each product are formed from 1.5 mol of Fe2O3.Products Fe and CO₂ are on the right side of the arrow.
Example 3
medium
In the reaction 2H2+O2→2H2O, identify the reactants and products.
Example 4
medium
In C3H8+5O2→3CO2+4H2O, calculate the moles of each product formed from 2.0 mol of C3H8.
Example 5
medium
When iron rusts: 4Fe+3O2→2Fe2O3. Identify the product and the chemical evidence that a reaction occurred.
Example 6
medium
Why is heat (or light) sometimes listed on the product side of an equation, and is heat a chemical product?
Example 7
hard
A student writes NaOH+HCl→NaCl+H2 and claims hydrogen gas is a product. What is wrong and what are the correct products?
Example 8
hard
Why must a catalyst (e.g., MnO2 in 2H2O2→2H2O+O2) not be listed as a product even though it ends up mixed with the products?
Example 9
challenge
Design an experiment to confirm that water is a product of the combustion of methane CH4+2O2→CO2+2H2O, distinguishing water vapor from CO2.
Practice Problems
Try these problems on your own first, then open the solution to compare your method.
Example 1
medium
When baking soda (NaHCO3) reacts with vinegar (acetic acid, CH3COOH), bubbles form. Identify the gas product and explain what evidence indicates a new product has formed.
Example 2
hard
In the Haber process, N2+3H2⇌2NH3, calculate the mass of ammonia (NH3) produced from 56.0 g of nitrogen gas reacting with excess hydrogen. (N = 14.01, H = 1.008g/mol)Haber process: N₂ + 3H₂ ⇌ 2NH₃. Calculate the mass of NH₃ produced.
Example 3
easy
In 2H2+O2→2H2O, name the product.Name the product — the substance on the right side of the arrow.
Example 4
easy
Which side of the arrow do products appear on?
Example 5
easy
In CH4+2O2→CO2+2H2O, list the products.List the products (right side) of this combustion reaction.
Example 6
easy
Is a catalyst a product even though it is present after the reaction?
Example 7
easy
Must products contain different elements than the reactants?
Example 8
easy
In 2Na+Cl2→2NaCl, what is the product?
Example 9
easy
What state symbol marks a gaseous product?
Example 10
easy
True or false: products are formed as the reaction proceeds.
Example 11
medium
In N2+3H2→2NH3, how many mol of product form from 2 mol N2 (with excess H2)?
Example 12
medium
In CaCO3→CaO+CO2, identify the products and which one is a gas.
Example 13
medium
If 23 g Na reacts fully with Cl2 to form NaCl (Na=23, Cl=35.5), what mass of product forms?
Example 14
medium
A precipitate forms when AgNO3(aq) meets NaCl(aq). Name the solid product and its state symbol.
Example 15
medium
Why does identifying the products require checking conservation of mass?
Example 16
medium
In 2H2O2→2H2O+O2 with a MnO2 catalyst, name the products and explain why MnO2 is not one.
Example 17
medium
Combustion of 1 mol CH4 gives how many mol of CO2 and H2O in CH4+2O2→CO2+2H2O?
Example 18
medium
A reaction produces a gas in an open beaker, and the beaker's mass drops. Where did the product go?
Example 19
medium
In 2Na+Cl2→2NaCl, how many mol of product form from 3 mol Na (excess Cl2)?
Example 20
challenge
A student writes H2+O2→H2O2 claiming hydrogen peroxide is the product of burning hydrogen. Critique using products and balancing.
Example 21
challenge
From 2C8H18+25O2→16CO2+18H2O, how many mol CO2 form from 4 mol octane, and why is CO2 a product?
Example 22
challenge
Two reactions form the same gas product. Design a test to confirm the product's identity rather than just its presence.
Example 23
easy
In Zn+2HCl→ZnCl2+H2, name all products.
Example 24
easy
True or false: the products and reactants must contain the same total number of each type of atom.
Example 25
easy
In the synthesis reaction 2Mg+O2→2MgO, name the product.
Example 26
easy
In HCl+NaOH→NaCl+H2O, name both products.
Example 27
easy
In a single replacement reaction, two products always form. True or false?
Example 28
medium
In CaCO3→CaO+CO2, what mass of CO2 is produced from 50.0 g of CaCO3? (M(CaCO3)=100.09, M(CO2)=44.01g/mol)
Example 29
medium
Predict the products of the neutralization H2SO4+2KOH→?
Example 30
medium
In 2KClO3→2KCl+3O2, how many moles of O2 are produced from 0.40 mol KClO3?
Example 31
medium
In 2Al+3Cl2→2AlCl3, how many moles of product form from 1.5 mol Cl2 (excess Al)?
Example 32
medium
In Mg(s)+CuSO4(aq)→MgSO4(aq)+Cu(s), identify the solid product and explain why it is solid.
Example 33
medium
In Zn+H2SO4→ZnSO4+H2, what volume of H2 gas at STP is produced from 0.20 mol Zn? (Molar volume at STP =22.4L/mol)
Example 34
hard
Combustion: 2C2H6+7O2→4CO2+6H2O. What mass of CO2 is produced from 9.0 g of ethane? (M(C2H6)=30.07, M(CO2)=44.01g/mol)
Example 35
hard
Limiting reagent: N2+3H2→2NH3 starts with 2.0 mol N2 and 3.0 mol H2. How much NH3 forms?
Example 36
hard
Percent yield: CaCO3→CaO+CO2. Decomposing 100.0 g of CaCO3 yields 50.0 g of CaO in practice. What is the percent yield? (M(CaCO3)=100.09, M(CaO)=56.08g/mol)
Example 37
hard
Gas test: an unknown reaction produces a gas that turns limewater milky. What is the gas, and write a balanced equation for the limewater test.
Example 38
challenge
A 10.00 g mixture of CaCO3 and inert sand is heated. After decomposition CaCO3→CaO+CO2 the solid mass is 7.80 g. What was the mass percent of CaCO3 in the original mixture? (M(CaCO3)=100.09, M(CO2)=44.01g/mol)