Key Calculations quiz

1. A sample of carbon contained 98.90% carbon-12 and 1.10% carbon-13. Calculate the relative atomic mass of carbon

(12x13)/100 = 1.56

((13x98.90)+(12x1.10))/100 = 12.99

(12+13)/2 = 12.5

((12x98.90)+(13x1.10))/100 = 12.01

Question 1 of 17

2. What volume does 3 moles of carbon dioxide gas occupy (at rtp)?

72 dm³

8 cm³

72 cm³

8 dm³

Question 2 of 17

3. A compound that contained 24.24% Carbon. 4.04% Hydrogen and 71.72% Chlorine and has a relative molecular mass of 99. Calculate the empirical formula and the molecular formula.

Empirical formula is CH₂Cl. Molecular formula is CH₂Cl

Empirical formula is C₂H₄Cl₂. Molecular formula is CH₂Cl

Empirical formula is C₂H₄Cl₂. Molecular formula is C₂H₄Cl₂

Empirical formula is CH₂Cl. Molecular formula is C₂H₄Cl₂

Question 3 of 17

4. To determine the formula of a metal oxide by combustion, magnesium is heated in a crucible. Why is the crucible is cooled, weighed, reheated, cooled, re-weighed, and so on?

To make sure a constant mass has been reached and there is no more magnesium left to react

To allow any water to escape

To make sure the mass is still going down so the magnesium is still reacting

To ensure all the magnesium oxide to escape

Question 4 of 17

5. What mass of carbon dioxide is produced when 24g of carbon undergoes completely combustion?

88g

24 g

44 g

176 g

Question 5 of 17

6. Use Q=mcΔT and c=4.18J/°C/g. 25cm³ of sulfuric acid is put into a boiling tube. The starting temperature is 21°C. A spatula of iron filings is added. After a while the temperature reaches 33°C. What is the total heat energy change?

2153 J

2.153 kJ

1254 J

3383 J

Question 6 of 17

7. 7.485 g of a hydrated copper(II) sulphate CuSO₄.xH₂O was heated producing 4.785g of anhydrous copper(II) sulphate. What is the formula of the hydrated salt?

CuSO₄.4H₂O

CuSO₄.7H₂O

CuSO₄.5H₂O

CuSO₄.10H₂O

Question 7 of 17

8. Describe how to carry out an acid-alkali titration

1) Pipette 25cm³ of alkali into a conical flask. 2) Add indicator. 3) Fill a burette with acid, record the initial volume. 4) Whilst swirling the flask, add the acid dropwise until the indicator changes colour. 5) Record the volume and calculate the volume of acid which was added. 6) Repeat until three concordant results (within 0.2cm³ of each other). 7) Result is the average of all concordant results.

1) Pipette 25cm³ of alkali into a conical flask. 2) Add indicator. 3) Fill a burette with acid, record the initial volume. 4) Whilst swirling the flask, add the acid dropwise until the indicator changes colour. 5) Record the volume and calculate the volume of acid which was added. 6) Repeat until two concordant results (within 0.2cm³ of each other). 7) Result is the average of all concordant results.

1) Pipette 25cm³ of alkali into a conical flask. 2) Add indicator. 3) Fill a burette with acid, record the initial volume. 4) Whilst swirling the flask, add the acid dropwise until the indicator is just about to change colour. 5) Record the volume and calculate the volume of acid which was added. 6) Repeat until two concordant results (within 0.2cm³ of each other). 7) Result is the average of all concordant results.

1) Pipette 25cm³ of alkali into a conical flask. 2) Add indicator. 3) Fill a burette with acid, record the initial volume. 4) Whilst swirling the flask, add the acid dropwise until the indicator is just about to change colour. 5) Record the volume and calculate the volume of acid which was added. 6) Repeat until three concordant results (within 0.2cm³ of each other). 7) Result is the average of all concordant results.

Question 8 of 17

9. What is meant by the term molecular formula?

A chemical formula that shows the simplest ratio of the numbers of atoms in a compound

A chemical formula that shows the actual numbers of the different types of atoms in a molecule

A method of calculating the ratios of masses in an equation

A method of calculating the mass needed to make a certain yield in an equation

Question 9 of 17

10. Calculate the relative formula mass(Mr) of aluminium nitrate (Al(NO₃)₃)

89

185

213

117

Question 10 of 17

11. What is the meaning of the word mole in Chemistry?

Moles are the units for amount of substance. (1 mole is 10 g of a substance)

Moles are the units for amount of substance. 1 mole of an element is its atomic number in grams (e.g. 1 mole of magnesium is 12 g)

Moles are the units for amount of substance. 1 mole of a substance is its relative formula mass in grams (e.g. 1 mole of magnesium is 24 g)

A mole is a small burrowing mammal

Question 11 of 17

12. In a chemical reaction, the overall molar enthalpy is -87 kJ/mol. Is this reaction exothermic or endothermic?

Depends on the reagents

Endothermic

Exothermic

Depends on the temperature of the surroundings

Question 12 of 17

13. A beaker of 2 dm³ of ammonium nitrate solution contains 1 mol of ammonium nitrate. What is the concentration of the solution?

2 mol/dm³

0.5 mol/dm³

0.0005 mol/dm³

0.5 dm³/mol

Question 13 of 17

14. What is the equation linking moles, Mᵣ and mass

Mᵣ = mass x moles

mass = moles / Mᵣ

moles = mass / Mᵣ

moles = mass x Mᵣ

Question 14 of 17

15. In the thermal decomposition of calcium carbonate, we might expect 50g of calcium carbonate to produce 28g of calcium oxide. If instead only 24g of calcium oxide is produced, what is the percentage yield?

0.857 %

56 %

0.56 %

85.7 %

Question 15 of 17

16. In a combustion calorimetry experiment, 0.78g of ethanol (C₂H₅OH) produced 12,540 J of heat energy. Calculate the molar enthalpy change.

-213 kJ/mol (Amount = 46/0.78 = 59.0 mol. Answer = 12540/59.0 = 213 kJ/mol)

-738 kJ/mol (Amount = 0.78/46 = 0.017 mol. Answer = 12540/1000/0.017 = 738 kJ/mol)

-425 kJ/mol (Amount = 23/0.78 = 29.5 mol. Answer = 12540/29.5 = 425 kJ/mol)

-369 kJ/mol (Amount = 0.78/23 = 0.034 mol. Answer = 12540/1000/0.034 = 369 kJ/mol)

Question 16 of 17

17. A graph shows the solubility of sodium chloride in water at 50°C is 34g/100g. At that temperature, what mass of sodium chloride will dissolve in 200g water?

0.34g

17g

68g

0.68g

Question 17 of 17

Key Calculations quiz

Related Posts:

Share This Story, Choose Your Platform!