Key Calculations quiz Loading... 1. To determine the formula of a metal oxide by combustion, magnesium is heated in a crucible. Why is a lid used?To stop carbon dioxide escapingTo stop the escape of magnesiumTo stop the escape of magnesium oxide smokeTo keep the magnesium warmQuestion 1 of 17 Loading... 2. An oxide of nitrogen contains 26% nitrogen and 74% oxygen and has a relative molecular mass of 108. Find the empirical and molecular formulae for the oxide.Empirical formula is N₂O₅. Molecular formula is also N₂O₅Empirical formula is N₂O₅. Molecular formula is N₄O₁₀Empirical formula is NO₂.₅ Molecular formula is N₂O₅Empirical formula is N₄O₁₀. Molecular formula is N₂O₅Question 2 of 17 Loading... 3. Use Q=mcΔT and c=4.18J/°C/g. A spatula of sodium fluoride is put into a boiling tube with 25cm³ of water. The temperature drops from 22.0°C to 18.6°C. What is the total heat energy change?1944 J355 kJ/mol1944 kJ355 JQuestion 3 of 17 Loading... 4. Complete the following expression: Mᵣ = amount (in moles) /massmass x amount (in moles)mass² / amount (in moles)mass / amount (in moles)Question 4 of 17 Loading... 5. State the units of molar enthalpy change.kJ/⁰Cmol/⁰CJ/⁰C/molkJ/molQuestion 5 of 17 Loading... 6. What is meant by the term molecular formula?A chemical formula that shows the simplest ratio of the numbers of atoms in a compoundA method of calculating the mass needed to make a certain yield in an equationA method of calculating the ratios of masses in an equationA chemical formula that shows the actual numbers of the different types of atoms in a moleculeQuestion 6 of 17 Loading... 7. What are the units for amount in Chemistry?g per 100g of solventMolesmol/dm³GramsQuestion 7 of 17 Loading... 8. State the expression for calculating molar concentrationMolar concentration = volume (in dm³) / Amount (in moles)Molar concentration = Amount (in moles) x volume (in cm³)Molar concentration = Amount (in moles)/volume (in cm³)Molar concentration = Amount (in moles)/volume (in dm³)Question 8 of 17 Loading... 9. What mass of carbon dioxide is produced when 24g of carbon undergoes completely combustion?88g44 g176 g24 gQuestion 9 of 17 Loading... 10. Calculate the relative formula mass(Mr) of aluminium oxide (Al₂O₃)4386129102Question 10 of 17 Loading... 11. State the steps for calculating empirical formula1) mass/Aᵣ. 2) divide by the smallest. 3) Give the ratio has a whole number. 4) State final empirial formula1) Aᵣ/mass. 2) divide by the largest. 3) Give the ratio has a whole number. 4) State final empirial formula1) mass/Aᵣ. 2) divide by the largest. 3) Give the ratio has a whole number. 4) State final empirial formula1) Aᵣ/mass. 2) divide by the smallest. 3) Give the ratio has a whole number. 4) State final empirial formulaQuestion 11 of 17 Loading... 12. Assuming bond energies in kJ/mol: H-C 412, C-C 348, O-H 463, C-O 360, C=C 612. Calculate the molar enthalpy change for the reaction: ethanol → ethene + water-45 kJ/mol (Some workings as follows. Breaking bonds 3231 kJ/mol. Making bonds 3186kJ/mol. Making - breaking = 3186-3231 = -45 kJ/mol)-45 kJ/mol (Some workings as follows. Breaking bonds 1583 kJ/mol. Making bonds 1487/mol. Making - breaking = 1487-1583 = -96 kJ/mol)+45 kJ/mol (Some workings as follows. Breaking bonds 3231 kJ/mol. Making bonds 3186kJ/mol. Breaking - making = 3231-3186 = +45 kJ/mol)+96 kJ/mol (Some workings as follows. Breaking bonds 1583 kJ/mol. Making bonds 1487/mol. Breaking - making = 1583-1487 = +96 kJ/mol)Question 12 of 17 Loading... 13. 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 50g water?68g0.17g17g0.68gQuestion 13 of 17 Loading... 14. State the expression for calculating % yield.% yield = (actual amount of products/theoretical amount of products) x 100% yield = (actual amount of products/theoretical amount of products)% yield = (theroretical amount of products/actual amount of products) x 100% yield = (theroretical amount of products/actual amount of products)Question 14 of 17 Loading... 15. What volume does 3 moles of carbon dioxide gas occupy (at rtp)?8 cm³72 cm³72 dm³8 dm³Question 15 of 17 Loading... 16. Describe how to carry out an acid-alkali titration1) 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 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 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 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 16 of 17 Loading... 17. A sample of bromine contained the two isotopes in the following proportions: bromine-79 = 50.7% and bromine-81 = 49.3%. Calculate the relative atomic mass of bromine(81 + 79)/2 = 80((79x50.7)+(81x49.3))/100 = 79.99(81x79)/100 = 63.99((81x50.7)+(79x49.3))/100 = 80.01Question 17 of 17 Loading... Related Posts:The entire quiz question bank!The entire quiz question bank (Double only)!Equilibria (triple) quizCondensation Polymers quizElectrolysis quizAlcohols & Carboxylic Acids quiz Hydr0Gen2020-02-16T17:35:16+00:00Categories: Uncategorized|Tags: Quiz, Topic: Key Calculations| Share This Story, Choose Your Platform! FacebookXRedditLinkedInTumblrPinterestVkEmail