A starting substance that is consumed and chemically transformed during a chemical reaction, appearing on the left side of a chemical equation before the reaction.
What you start with — the ingredients that get used up to make something new.
Showing a random 20 of 50 problems.
Example 1
hard
A student writes 'water is a reactant in the dissolution of NaCl in water'. Critique this.
Example 2
easy
In an aqueous reaction, is the water solvent always a reactant?
Example 3
medium
In 2H2+O2→2H2O, if you start with 4 mol H2 and 1 mol O2, which reactant runs out first?
Example 4
medium
In CaCO3→CaO+CO2, identify the single reactant and explain decomposition.How many reactants are on the left side of this decomposition reaction?
Example 5
easy
In CH4+2O2→CO2+2H2O, is oxygen a reactant or product?Is O₂ on the left (reactant) or the right (product)?
Example 6
easy
Which side of the arrow do reactants appear on?
Example 7
medium
Given Pb(NO3)2(aq)+2KI(aq)→PbI2(s)+2KNO3(aq), list reactants and how to verify mass conservation.
Example 8
easy
In 2H2+O2→2H2O, name the reactants.Which substances are on the left side of the arrow?
Example 9
easy
In the reaction Mg+2HCl→MgCl2+H2, name the reactants.
Example 10
medium
Why must you know the reactants before you can balance an equation?
Example 11
medium
A flask shows HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l). Which reactant is the acid?
Example 12
medium
For C2H5OH+3O2→2CO2+3H2O, how many moles of O2 react with 0.50 mol ethanol?
Example 13
hard
For 2Al+3CuSO4→Al2(SO4)3+3Cu, 0.20 mol Al and 0.20 mol CuSO4 are mixed. Which reactant limits product formation?
Example 14
challenge
Two reactions share the same catalyst but different reactants. Explain how you would experimentally tell reactants from the catalyst.
Example 15
medium
In photosynthesis 6CO2+6H2O→C6H12O6+6O2, is water a reactant here?
Example 16
medium
In AgNO3(aq)+NaCl(aq)→AgCl(s)+NaNO3(aq), name the reactants and the role of water.
Example 17
medium
A reaction has reactants A and B plus a catalyst K. After reacting, K is fully recovered. Which are reactants?
Example 18
easy
True or false: a substance whose mass increases during a reaction is a reactant.
Example 19
easy
Is a catalyst counted as a reactant in the net equation?
Example 20
easy
In an enzyme-catalyzed reaction, is the enzyme a reactant?