Limiting & Excess Reagent
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1 / 55
10 g of hydrogen and 64 g of oxygen were filled in a steel vessel and exploded. Amount of water produced in this reaction will be
Audio Explanation
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2 / 55
NH₃ is obtained by the combination of N₂ and H₂, as shown by the following balanced equation:
N₂(g) + 3H₂(g) → 2NH₃(g)
What mole of H2 required to manufacture 5.0 moles of NH₃?
Explanation:
Balanced equation: N₂(g) + 3 H₂(g) → 2 NH₃(g)
n(H₂) = (3 mol H₂ / 2 mol NH₃) × 5.0 mol NH₃ = (3/2) × 5.0 mol = 7.5 mol H₂
3 / 55
When 10 g of calcium reacts with 10 g of water according to the following reaction:
Ca + 2H₂O → Ca(OH)₂ + H₂Find the limiting reagent and the number of moles of hydrogen gas (H₂) formed.
Moles of Ca = 10 / 40 ≈ 0.25 mol
Moles of H₂O = 10/ 18 ≈ 0.55 mol
Limiting Reagent Trick: Ca + 2H₂O → Ca(OH)₂ + H₂ divide the given moles with the coefficient For Ca: 0.25/1=0.25 For H₂O: 0.55/2 ≈ 0.28 So: 0.25 is less than 0.28 so we can say Ca is the limiting reagent
From the equation, 1 mol Ca → 1 mol H₂, so H₂ formed = ≈ 0.25 mol.
4 / 55
If only 4.4 moles of ZnCO3 were decomposed, how many grams of CO2 would be produced?
If 4.4 moles of ZnCO3 are decomposed, then 4.4 moles of CO2 will be produced, as the mole ratio is 1:1. To find the mass:
4.4moles×44g/mol =193.6g
5 / 55
In a reaction, 56g of iron completely reacts with 64g of sulphur. Which reactant is in excess, and by how much?
The reaction requires equal moles of iron and sulphur (1:1 ratio). Given 56 g of iron (1 mole) reacts with only 32 g of sulphur (1 mole), leaving 64−32=32 g of sulphur in excess.
6 / 55
How many mole of O, is needed to react completely with 6 mole of Al ? [Given Atomic maas of Al = 27]
Al + O2→ AL2O3
lets write the balance chemical equation:
From the balanced equation:
4 moles of Al react with 3 moles of O₂.
So,
7 / 55
For 2H2 + O2 → 2H2O, if you have 5 mol H2 and 2 mol O2, the limiting reagent is:
Use this short trick: Given/Coefficient (Just divide the given mole with Coefficient value the one with smaller answer is limiting reagent ) for O2 Given is 2 and Coefficient is 1 so 2/1=2 for H2 Given is 5 and Coefficient is 2 so 5/2=2.5 we can clearly see 2 is less than 2.5 so O2 is limiting reagent
8 / 55
N2 + 3H2 → 2NH3. If 28 g N2 and 6 g H2 are mixed, which is limiting?
its a balance chemical equation Ratio is exactly 1:3 as per the chemical equation so we do not have any limiting reagent here. N2 + 3H2 → 2NH3.
n(N2)=28/28=1 mol; n(H2)=6/2=3 mol. Ratio exactly 1:3, so neither limits; both are fully consumed.
9 / 55
in the reaction: 2H₂ + O₂ → 2H₂O, if 5 moles of H₂ and 2 moles of O₂ are mixed, the limiting reagent is:
Balanced reaction: 2 H2 + 1 O2 → 2 H2ORequired mole ratio H2:O2 = 2:1.
• Limiting check trick: divide moles by coefficients. Smaller value limits.Here: H₂ → 5/2= 2.5; O₂ → 2/1 = 2 ⇒ O₂ is limiting.
• Leftover (excess) reactant: H₂ left = 5 − (2×2) = 1 mol.
• Product from limiter: H₂O = 2 × (O₂ used) = 2 × 2 = 4 mol.
H2 consumed = 4 mol; H2 left over = 5 − 4 = 1 mol (excess).
H2O formed = 2×(moles of O2 used) = 2×2 = 4 mol.
TRICK
Moles ko apne stoichiometry coefficient se divide karo; jo small ho woh limiting.
10 / 55
In the reaction N2(g)+3H2(g)→2NH3(g), if 5.0 moles of N2 and 9.0 moles of H2 are mixed, the limiting reactant is:
The required mole ratio (N2:H2) is 1:3.
Divide moles by coefficient:
N2: 5.0/1=5.0 H2: 9.0/3=3.0
The smallest resulting value (3.0 for H2) indicates the limiting reactant.
11 / 55
To accurately calculate the maximum possible mass of product (theoretical yield), a chemist must always base the calculation on the quantity of the:
The limiting reactant dictates exactly when the reaction must stop, thus setting the upper bound for the amount of product that can theoretically be formed.
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How much volume of NH₃ gas is produced when 3 g H₂ react with excess of N₂ at STP?
Step 1: Write the balanced equation
N2 + 2H2→2NH3
Step 2: Calculate moles of H₂
Step 3: Use the stoichiometric ratio
From the equation:3 mol H₂ → 2 mol NH₃
So, Step 4: Convert moles of NH₃ to volume at STP
At STP, 1 mol of any gas = 22.4 dm³ Closest to 24dm3
13 / 55
Which sample produces most hydrogen by reaction with excess of HCl?
(a) Ca + 2HCl → CaCl₂ + H₂→ 1 mol Ca gives 1 mol H₂
(b) 2Al + 6HCl → 2AlCl₃ + 3H₂→ 2 mol Al give 3 mol H₂→ 1 mol Al gives 1.5 mol H₂
(c) Zn + 2HCl → ZnCl₂ + H₂→ 1 mol Zn gives 1 mol H₂
(d) 2Na + 2HCl → 2NaCl + H₂→ 2 mol Na give 1 mol H₂→ 1 mol Na gives 0.5 mol H₂
14 / 55
When equal volumes of SO₂ and O₂ are taken for the formation of SO₃, which one will be left unreacted?
2 SO2 + O2 → 2 SO3 Required volume (mole) ratio SO2:O2 = 2:1. Given equal volumes ⇒ ratio 1:1. Compared to 2:1, SO2 is limiting; O2 is in excess. Hence O2 remains unreacted.
15 / 55
what volume of SO2 at room temp and pressure is produced on heating 9.7g of zinc supplied (ZnS) if reaction takes place as follows
2ZnS + 3O2 →2ZnO + 2SO2
Calculate the moles of ZnS: Moles = Mass / Molar Mass = 9.7 g / 97.5 g/mol ≈ 0.1 moles of ZnS.
From the equation 2ZnS ⟶ 2SO₂, the mole ratio is 1:1, so 0.1 moles of SO₂ are produced.
Calculate the volume at Room Temperature and Pressure (RTP), where 1 mole of any gas is 24 dm³. Volume = 0.1 mol × 24 dm³/mol = 2.4 dm³.
16 / 55
if four moles of SO2 are oxidized to SO3 how many moles of oxygen molecules are required
Reaction: 2 SO₂ + O₂ → 2 SO₃ For 4 mol SO₂, needed O₂ = 1/2×4=2 mol.
17 / 55
How many moles of oxygen are needed for the complete combustion of two moles of butane
Balanced: C₄H₁₀ + 6.5 O₂ → 4 CO₂ + 5 H₂O.For 2 moles butane: 2 × 6.5 = 13 moles O₂.
18 / 55
The reactant which is consumed earlier and gives least quantity of product is called
The limiting reactant is completely consumed first in a reaction and thus limits the amount of product formed (i.e., gives the least quantity of product).
“Stoichiometric amount” means exactly the proportions required by the balanced equation, “reactant in excess” is the one left over, and “stoichiometry” is the calculation method, not a reactant.
19 / 55
a limiting reactant is the one which:
A limiting reactant is the substance that is completely consumed first in a chemical reaction.Once it’s used up, no more product can form, thus it limits the reaction and determines the minimum (actual) amount of product possible.Excess reactants remain unreacted after the reaction is complete.
20 / 55
27g of Al will react completely with how much mass of O2 to produce Al2O3
Balanced equation: 4Al + 3O₂ → 2Al₂O₃.27 g Al = 1 mol Al; required O₂ moles = (3/4)×1 = 0.75 mol.Mass of O₂ = 0.75 × 32 g/mol = 24 g.
21 / 55
Carbonic acid (H₂CO₃) can be prepared according to the following reaction:
CO₂ (g) + H₂O (l) → H₂CO₃ (aq)
If 120 g of CO₂ is dissolved in 80 g of water, then Identify the limiting reagent
Mass of CO₂ = 120 gMolar mass of CO₂ = 12 + (2 × 16) = 44 g/molMoles of CO₂ = 120 g / 44 g/mol = 2.72 mol
Mass of H₂O = 80 gMolar mass of H₂O = (2 × 1) + 16 = 18 g/molMoles of H₂O = 80 g / 18 g/mol = 4.44 mol
From the balanced equation:1 mol CO₂ reacts with 1 mol H₂OSo, to react with 2.72 mol of CO₂, we need 2.72 mol of H₂O
But we have 4.44 mol of H₂O, which is more than enough. Limiting Reagent = CO₂, because it will be completely used first.
22 / 55
If 67.5 g of Aluminum (Al) and 140 g of Nitrogen gas (N₂) are allowed to react, find out the Mass of excess reactant
(Atomic mass: Al = 27 a.m.u, N = 14 a.m.u)
Mass of N₂ available = 140 g
Molar mass of N₂ = 28 g/mol
Moles of Al = 2.5 mol
Balanced equation:2Al + N₂ → 2AlN
Step 1: Calculate moles of nitrogen (N₂) available
Moles of N₂ = Mass / Molar massMoles of N₂ = 140 g / 28 g/mol = 5 mol
Step 2: Determine how many moles of N₂ are required
From the balanced chemical equation:2 mol Al reacts with 1 mol N₂So, 2.5 mol Al would react with:(1 mol N₂ / 2 mol Al) × 2.5 mol Al = 1.25 mol N₂
Step 3: Calculate moles of N₂ remaining
Remaining moles of N₂ = Initial − UsedRemaining moles = 5 mol − 1.25 mol = 3.75 mol
Step 4: Convert remaining moles of N₂ to mass
Mass = Moles × Molar massMass = 3.75 mol × 28 g/mol = 105 g
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If 67.5 g of Aluminum (Al) and 140 g of Nitrogen gas (N₂) are allowed to react, find out the Mass of Aluminum nitride (AlN) produced
Moles of AlMolar mass of Al = 27 g/molMoles of Al = 67.5 g / 27 g/mol = 2.5 moles
From the balanced equation:2 mol Al → 2 mol AlNSo, 2.5 mol Al will produce 2.5 mol AlN
Molar mass of AlN = 27 (Al) + 14 (N) = 41 g/mol
Mass of AlN = 2.5 mol × 41 g/mol = 102.5 g
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If 67.5 g of Aluminum (Al) and 140 g of Nitrogen gas (N₂) are allowed to react, find out the Limiting reactant
Moles of N₂Molar mass of N₂ = 2 × 14 = 28 g/molMoles of N₂ = 140 g / 28 g/mol = 5 moles
From the balanced equation:2Al + N₂ → 2AlN
2 moles of Al react with 1 mole of N₂
So, 2.5 moles of Al would need:(1 mol N₂ / 2 mol Al) × 2.5 mol Al = 1.25 mol of N₂
But we have 5 mol of N₂, which is more than enough.Limiting Reactant = Aluminum (Al)
25 / 55
Combustion of ethene (C₂H₄) in air to form CO₂ and H₂O is given by the following balanced equation:C₂H₄ + 3O₂ → 2CO₂ + 2H₂O. If a mixture containing 2.8 g of C₂H₄ and 6.4 g of O₂ is allowed to ignite. Determine the mass of CO₂ gas that will be formed
Moles of O₂Molar mass = 2 × 16 = 32 g/molMoles = 6.4 g / 32 g/mol = 0.2 mol
NOW
Step 1: Use mole ratio from equation3 mol O₂ → 2 mol CO₂So, 0.2 mol O₂ →(0.2 × 2) / 3 = 0.133 mol CO₂
Step 2: Calculate mass of CO₂Molar mass of CO₂ = 12 + (16 × 2) = 44 g/molMass = 0.133 mol × 44 g/mol = 5.867 g
26 / 55
Combustion of ethene (C₂H₄) in air to form CO₂ and H₂O is given by the following balanced equation:C₂H₄ + 3O₂ → 2CO₂ + 2H₂OIf a mixture containing 2.8 g of C₂H₄ and 6.4 g of O₂ is allowed to ignite. Identify the limiting reactant
Step 1: Calculate moles of each reactant
Moles of C₂H₄Molar mass = (2 × 12) + (4 × 1) = 28 g/molMoles = 2.8 g / 28 g/mol = 0.1 mol
Step 2: Use mole ratio to find the limiting reactantFrom the balanced equation:1 mol of C₂H₄ reacts with 3 mol of O₂So, 0.1 mol of C₂H₄ would require:0.1 × 3 = 0.3 mol of O₂
Only 0.2 mol of O₂ is available, which is less than 0.3 mol.
Limiting Reactant = O₂
27 / 55
Magnesium metal reacts with sulphur to produce MgS. How many grams of magnesium sulphide (MgS) can be made from 1.50 g of Mg and 1.50 g of sulphur by the reaction:
Mg + S → MgS
Mass of Mg = 1.50 g
Molar mass of Mg = 24 g/mol
Moles of Mg = (Mass of Mg) / (Molar mass of Mg)= 1.50 g / 24 g/mol = 0.0625 moles
Mass of S = 1.50 g
Molar mass of S = 32 g/mol
Moles of S = (Mass of S) / (Molar mass of S)= 1.50 g / 32 g/mol = 0.0468 moles
From the balanced equation:1 mole of Mg reacts with 1 mole of S to produce 1 mole of MgS.
Since there are fewer moles of S (0.0468) than Mg (0.0625), Sulphur (S) is the limiting reactant.
Since S is the limiting reactant, the moles of MgS produced will be equal to the moles of S used.
Moles of MgS = 0.0468 moles
Molar mass of MgS = 24 (Mg) + 32 (S) = 56 g/mol
Mass of MgS = Moles × Molar mass = 0.0468 × 56 = 2.6208 g
28 / 55
Mass of 49 g of solid potassium chlorate (KClO₃) on heating decomposes completely to potassium chloride (KCl) with the liberation of oxygen gas (O₂).Determine the volume of oxygen gas (O₂) liberated at STP.
Chemical Equation:2KClO₃ (s) → 2KCl (s) + 3O₂ (g)
Step 1: Calculate moles of KClO₃
Molar mass of KClO₃ = 39 (K) + 35.5 (Cl) + 3 × 16 (O) = 122.5 g/mol
Moles of KClO₃ = (Given mass) / (Molar mass)= 49 g / 122.5 g/mol = 0.4 moles
Step 2: Determine moles of O₂ produced
From the balanced equation, 2 moles of KClO₃ produce 3 moles of O₂
Therefore, 1 mole of KClO₃ produces 3/2 moles of O₂
So, 0.4 moles of KClO₃ will produce (3/2) × 0.4 = 0.6 moles of O₂
Step 3: Calculate volume of O₂ at STP
At STP, 1 mole of any gas occupies 22.4 dm³
Volume of 0.6 moles of O₂ = 0.6 × 22.4 = 13.44 dm³
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Calculate the mass of carbon dioxide (CO₂) that can be obtained by the complete thermal decomposition of 50 g of limestone (CaCO₃).
Chemical Equation:CaCO₃ (s) → CaO (s) + CO₂ (g)
Step 1: Calculate moles of CaCO₃
Molar mass of CaCO₃ = 40 (Ca) + 12 (C) + 3 × 16 (O) = 100 g/mol
Moles of CaCO₃ = (Given mass) / (Molar mass)= 50 g / 100 g/mol = 0.5 moles
Step 2: Determine moles of CO₂ produced
From the balanced equation, 1 mole of CaCO₃ produces 1 mole of CO₂
Therefore, 0.5 moles of CaCO₃ will produce 0.5 moles of CO₂
Step 3: Calculate mass of CO₂
Molar mass of CO₂ = 12 (C) + 2 × 16 (O) = 44 g/mol
Mass of CO₂ = Moles × Molar mass= 0.5 mol × 44 g/mol = 22 g
30 / 55
How many moles of oxygen (O₂) are produced when 10 moles of potassium chlorate (KClO₃) decompose?
2KClO₃ → 2KCl + 3O₂
Balanced equation:2KClO₃ → 2KCl + 3O₂From the equation:2 moles of KClO₃ → 3 moles of O₂This means:1 mole of KClO₃ → 1.5 moles of O₂So, for 10 moles of KClO₃:10 × 1.5 = 15 moles of O₂
31 / 55
what mass of aluminum oxide (Al2O3) is produced from 18.5g of Al metal, when it reacts completely with oxygen gas according to the following equation
4Al(S) + 302(g) - 2Al2O3(S)
Molar mass of Al= 27g/mol, Molar mass of Al2O3= 102g/mol
Moles of Al= 18.5/27= 0.6mol
Moles of Al2O3= 2/4 (0.6)= 0.34mol
Mass of Al2O3= (0.34)(102)= 34.9g
32 / 55
How many grams of CO2 can be produced by thermally decomposing 10 moles of ZnCO3?
ZnCO₃→ZnO+CO₂ From the balanced equation, 1 mole of ZnCO₃ produces 1 mole of CO₂. Therefore, 10 moles of ZnCO₃ will produce 10 moles of CO₂.
The molar mass of CO₂ is: C=12g/mol, O₂=16×2=32g/mol ⇒ Molar mass of CO₂=12+32=44g/mol C=12g/mol,O₂=16×2=32g/mol ⇒Molar mass of CO₂=12+32=44g/mol For 10 moles of CO₂:
Mass of CO₂ =10moles×44g/mol=440g
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2H₂ + O₂ → 2H₂OIf 4 moles of H₂ react with 1 mole of O₂, which is the limiting reagent?
Reaction needs 2 mol H₂ for 1 mol O₂. For 1 mol O₂, required H₂ = 2 mol. We have 4 mol H₂ (extra). O₂ finishes first, so O₂ is limiting.
34 / 55
the reaction 2X+4Y⟶3C+4D, if 5 moles of X reacts with 6 moles of Y then, which is the limiting reagent?
The balanced reaction is as follows: 2A+4B→3C+4D
No. of moles given: 5,6
Stoichiometry coefficients given: 2,4
Ratio of moles given and stoichiometry coefficients:
For X: 5/2 = 2.5
For Y: 6/4 = 1.5As 1.5 is lower than 2.5, B is limiting reagent as it will be consumed first.
35 / 55
If the mass of HCl used in the reaction between HCL and NaOH (Neutralization Reaction) doubled, how many moles of NaCl would be produced if initial mass of HCl is 15.5g?
KPK Book Example
If the mass of HCl is doubled from 15.5 g to 31.0 g, then the moles of HCl will also double: Moles=31/36.5 moles=0.850 mol
36 / 55
4.4moles×44g/mol=193.6g
37 / 55
If the decomposition of potassium chlorate (KClO3) produces 15 moles of oxygen gas, how many moles of potassium chloride(KCl) will be formed?
From the equation:2 moles of KClO₃ produce:→ 2 moles of KCl→ 3 moles of O₂
This gives us the mole ratio: KCl:O2 =2 :3
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39 / 55
If 2 moles of iron react completely with 96g sulphur , what is the mass of iron sulphide produced?
Reference: KPK Book Example
The reaction requires equal moles of iron and sulphur to form iron sulphide.
Since the reaction will limit to the smaller stoichiometric ratio (2 moles of iron), it will react with 2 moles of sulphur (64 g). Therefore, the mass of iron sulphide produced is: 2 × 88 =176 g
40 / 55
the reactant which consumed first in a chemical reaction is called as
The limiting reagent in a chemical reaction is the reactant that will be consumed completely. Once there is no more of that reactant, the reaction cannot proceed. Therefor it limits the reaction from continuing. The excess reagent is the reactant that could keep reacting if the other had not been consumed.
41 / 55
How many moles of CO₂ are produced when 4.4 moles of ZnCO₃ decompose completely?
42 / 55
If only 5 moles of KClO₃ are available, how many moles of O₂ will be produced on decomposition of KClO3?
The balanced chemical equation shows that 2 moles of KClO₃ produce 3 moles of O₂. Therefore, 5 moles of KClO₃ will produce: moles of O2=(3/2)×5=7.5 moles
43 / 55
The volume in dm^3 of oxygen required to form 36 g of H2O on burning with H2 gas is?
44 / 55
Which of the following control the amount of product?
The limiting reagent controls the amount of product formed in a chemical reaction.
The limiting reagent (or limiting reactant) is the substance that is completely consumed first in a reaction, thereby determining the maximum amount of product that can be formed. Once the limiting reagent is used up, the reaction stops, and no more product can be produced, even if other reactants are still available in excess.
45 / 55
In a reaction, 2 moles of substance X react with 3 moles of substance Y to produce 4 moles of product Z, If there are 6 moles of X and 5 moles of Y available, which one is limiting reagent?
46 / 55
36 g glucose was dissolved in water to form solution Glucose + Water → Solution What is limiting reagent?
In this process, glucose (solute) is dissolved in water (solvent) to form a solution.The limiting reagent is the substance that is completely used up first — here, glucose — because water is present in large excess and does not limit the formation of the solution.
47 / 55
Carbonic acid H2CO3 can be prepared according to the following reaction If 120g of CO2 is dissolved in 80g of water then, what will be the limiting reagent
Convert Gram into moles and from balance chemical equation we can see that
now 120 g of CO2 produced a smaller number of moles of H2CO3 so it is limiting reagent
48 / 55
How many ZnO can be produced by decomposing 4 moles of ZnCO3
Write the balanced decomposition reaction: ZnCO₃ → ZnO + CO₂
From the equation, 1 mol ZnCO₃ produces 1 mol ZnO.
4 mol ZnCO₃ × = 4 mol ZnO
49 / 55
Oxygen can be prepared by the decomposition of potassium chlorate KClO3. How many moles of O2 can be formed by taking 40 moles of KClO3
50 / 55
How many moles of carbon dioxide can be Produced by the complete combustion of 4 Moles of Glucose
51 / 55
How many grams of CO2 can be produced by thermally decomposing 2 moles of ZnCo3 (s)
52 / 55
What is the amount of water produced when 8g of hydrogen is reacted with 32g of oxygen?
The chemical equation of water formation is 2H2 + O2 → 2H2O. Though we have 8g of hydrogen, here oxygen is the limiting reagent. So only 4g of hydrogen can be used to produce water i.e. 36g of water. That is 2 moles.
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In a particular reaction, one of the reactants limits the number of products formed. That is called as _______
Though the other substances are excess in amount than the required, each and every reactant needs to be in a fixed ratio to attain the desired product. So, thereby, the reactant that limits the quantity of the product formed is called limiting reagent and this reactant gets consumed first completely.
54 / 55
Limiting reactant in any reaction is the one?
Limiting reactant in any reaction is the one that is consumed earlier
55 / 55
Zirconium chloride reacts with magnesium to produce Zirconium. ZrCI4 + 2Mg → Zr + 2MgCI2 How many moles Zr would be produced if 0.2 mol of Mg metal is used in the reaction?
2 moles of Mg produce 1 mole of Zn. So 0.2 moles would produce 0.1 mole of Zn.
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