MOLES & MOLAR MASS
EMPERICAL & MOLECULAR FORMULA
CHEMICAL REACTIONS & EQUATIONS
ATP - TITRATION
ATP- GENERAL QUESTIONS
100

Calculate the number of moles in 12.5 g of sodium carbonate .

0.118 moles


100

A compound contains 40% sulfur and 60% oxygen by mass. Calculate the empirical formula.

SO₃

100

Balance the following chemical equation: 

C₃H₈ + O₂ --> CO₂ + H₂0

C₃H₈ + 5O₂ --> 3CO₂ + 4H₂0

100

What is the purpose of using a phenolphthalein indicator in an acid-base titration?

To determine the endpoint by changing color when the solution transitions from acidic to basic (colorless in acid to pink in base

100

What is the primary purpose of using a control experiment in practical chemistry?

To provide a baseline for comparison, ensuring that the observed effect is due to the variable being tested. 

200

if 4.4 g of carbon dioxide is produced in a reaction , how many molecules of CO2 are formed ?

6.02x10²² molecules

200

A compound has an empirical formula of CH₂O and a molar mass of 180 g/mol. What is the molecular formula of the compound?

C₆H₁₂O₆

200

Write the balanced chemical equation for the complete combustion of ethanol

C₂H₅OH + 3O₂ --> 2CO₂ + 3H₂0

200

In a titration, 25.0 cm³ of 0.1 M hydrochloric acid (HCl) is neutralized by 20.0 cm³ of sodium hydroxide (NaOH). What is the concentration of the NaOH solution?

0.125 M

200

When measuring the volume of a liquid using a burette, why is it important to remove the air bubble from the tip before starting the titration?  

To ensure accurate volume measurement and avoid errors caused by air pockets.

300

Calculate the mass of oxygen gas required to completely react with 0.5 moles of ethane in the following reaction : 

2C2H6+7O2→4CO2+6H2O


112 g

300

Determine the empirical formula of a compound that contains 92.3% carbon and 7.7% hydrogen by mass.

CH

300

A 10 g sample of calcium carbonate (CaCO₃) decomposes upon heating according to the following reaction:
CaCO3(s)→CaO(s)+CO2(g) 

Calculate the mass of calcium oxide (CaO) produced.

5.6 g

300

A titration experiment requires 24.5 cm³ of 0.1 M NaOH to neutralize 25.0 cm³ of sulfuric acid (H₂SO₄). Calculate the concentration of the sulfuric acid.

0.049 M

300

Explain why it is important to rinse the inside of a conical flask with distilled water during a titration but not with the titrant.

Rinsing with distilled water does not affect the concentration of the solution in the flask, ensuring that only the titrant reacts with the analyte.

400

 A sample of hydrated copper(II) sulfate, CuSO₄∙xH₂O, weighs 6.25 g. After heating, 4.00 g of anhydrous CuSO₄ remains. Determine the value of x  

x = 5

400

A compound contains 27.3% carbon, 72.7% oxygen by mass, and has a molar mass of 88 g/mol. Determine the molecular formula.

C₂O₄

400

Balance the following redox reaction in acidic solution 

MnO4⁻ + Fe2⁺ → Mn2⁺ + Fe3⁺ 

MnO4⁻ + 5Fe2⁺ +8H⁺→Mn2⁺+5Fe3⁺ + 4H2O

400

Calculate the percentage purity of a sample of sodium carbonate (Na₂CO₃) if 1.06 g of the sample requires 25.0 cm³ of 0.1 M hydrochloric acid (HCl) for complete neutralization.

50%

400

In a reaction to determine the concentration of an unknown solution using a standard solution, why is it crucial to perform multiple titrations and calculate an average volume used?

To increase the accuracy and reliability of the results by minimizing random errors and ensuring that any anomalies or inconsistencies in individual titrations do not skew the final concentration calculation.

500

Calculate the empirical formula of a hydrocarbon that is 85.7% carbon and 14.3% hydrogen by mass.

C₇H₁₆

500

A hydrocarbon contains 80% carbon and 20% hydrogen by mass. If the molar mass of the compound is 30 g/mol, calculate the molecular formula.

C₂H₆

500

Given the reaction:
2Na2O2 + 2H2O → 4NaOH + O2
Calculate the volume of oxygen gas produced at room temperature and pressure (RTP) when 10 g of sodium peroxide (Na₂O₂) reacts completely with water.

1.54 dm³

500

During a titration, 0.5 g of impure oxalic acid (H₂C₂O₄) was titrated with 0.1 M NaOH. The titration required 25.0 cm³ of NaOH to reach the endpoint. Calculate the percentage purity of the oxalic acid.

55.6%

500

In a qualitative analysis, why is it important to add reagents in a specific order when testing for multiple ions in a single solution?

To prevent the formation of precipitates that could obscure the results, as adding reagents in the wrong order could cause interfering reactions or mask the presence of certain ions.

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