Quantitative chemistry

The formula of a compound is N₂O. How many of each type of atom are in one molecule of N₂O?

The student used a solution of sodium hydroxide of concentration 4.00 g/dm³. Calculate the mass of sodium hydroxide in 25.0 cm³ of this solution. (1 dm³ = 1000 cm³)

12 g of carbon contains 6.02 × 10²³ atoms. Which expression is used to calculate the mass of one atom of carbon?

Calculate the relative formula mass (Mᵣ) of Fe₂O₃.\nRelative atomic masses (Aᵣ): O = 16, Fe = 56

Copper oxide reacts with hydrogen to produce copper.\nThe equation for the reaction is: CuO + H₂ → Cu + H₂O\nCalculate the percentage atom economy for obtaining copper from this reaction.\nUse the equation: Percentage atom economy = (Mᵣ of desired product / Total Mᵣ of reactants) × 100\nRelative atomic mass (Aᵣ): Cu = 63.5\nRelative formula masses (Mᵣ): H₂ = 2, CuO = 79.5

The discovery of isotopes explained why some relative atomic masses are not whole numbers. Element R has two isotopes. Table 5 shows the mass numbers and percentage abundances of the isotopes of element R. <br/><br/> <div style="font-family: Arial, sans-serif; max-width: 400px;"> <h3 style="text-align: center; margin-bottom: 5px;">Table 5</h3> <table style="width: 100%; border-collapse: collapse; text-align: center; border: 1px solid #000;"> <thead> <tr style="background-color: #ffffff;"> <th style="border: 1px solid #000; padding: 10px; width: 50%;">Mass number</th> <th style="border: 1px solid #000; padding: 10px; width: 50%;">Percentage abundance (%)</th> </tr> </thead> <tbody> <tr> <td style="border: 1px solid #000; padding: 10px;">6</td> <td style="border: 1px solid #000; padding: 10px;">7.6</td> </tr> <tr> <td style="border: 1px solid #000; padding: 10px;">7</td> <td style="border: 1px solid #000; padding: 10px;">92.4</td> </tr> </tbody> </table> </div> <br/><br/> Calculate the relative atomic mass (Aᵣ) of element R. <br/><br/> Give your answer to 1 decimal place.

The maximum theoretical mass of the salt that could be produced using 50 cm³ of the sulfuric acid is 12.5 g. The percentage yield of the salt is 92.8%. Calculate the mass of salt actually produced. Use the equation: % yield = (mass of salt actually produced / maximum theoretical mass of salt that could be produced) × 100

A different student repeated steps 1 to 5 of the method four times using 0.50 g of zinc powder. Table 2 shows the results. <br/><br/> <table border="1" cellpadding="12" cellspacing="0" style="border-collapse: collapse; font-family: Arial, sans-serif; font-size: 15px; border: 2px solid black;"> <caption style="font-weight: bold; font-size: 18px; margin-bottom: 10px;">Table 2</caption> <tr> <th style="border: 1px solid black; padding: 12px;"></th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Trial 1</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Trial 2</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Trial 3</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Trial 4</th> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Highest temperature reached in °C</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">37.6</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">37.2</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">37.8</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">37.4</td> </tr> </table> <br/><br/> Calculate the mean highest temperature reached. Include the uncertainty in your answer.

When iron reacts with chlorine, 0.12 mol of iron reacts with 0.18 mol of chlorine (Cl₂). Which is the correct equation for the reaction?

Calculate the percentage (%) by mass of iron in Fe₃O₄. Relative atomic masses (Aᵣ): O = 16, Fe = 56

Fe₂O₃ reacts with carbon to produce carbon dioxide. The equation for the reaction is: 2Fe₂O₃(s) + 3C(s) → 4Fe(s) + 3CO₂(g) Calculate the volume of carbon dioxide gas at room temperature and pressure that is produced from 40.0 kg of Fe₂O₃ using excess carbon. Relative formula mass (Mᵣ): Fe₂O₃ = 160 The volume of 1 mole of any gas at room temperature and pressure is 24 dm³.

The student titrated a solution containing 0.0045 moles of sodium hydroxide with 0.15 mol/dm³ hydrochloric acid. The equation for the reaction is: NaOH + HCl → NaCl + H₂O Calculate the volume of hydrochloric acid in cm³ needed in the titration.

A student heats 2.5 g of hydrated copper sulfate in a test tube. 0.9 g of water is given off. The remaining solid is anhydrous copper sulfate. Calculate the mass of anhydrous copper sulfate produced.

Calculate the percentage of water contained in 2.5 g of hydrated copper sulfate. (Mass of water = 0.9 g)

What is the chemical formula for Copper sulfate?

What is the chemical formula for Water?

A firefighter uniform made from polymer J has a mass of 6.0 kg. Calculate the mass of a uniform of the same size made from polymer K. Use Table 1 and the equation: mass of uniform made from polymer K = (density of polymer K / density of polymer J) × 6.0

A 9 carat gold ring is made from a mixture of metals. The mass of the ring is 5.0 g. Table 3 shows the mass of different metals in the ring. Plot the data for copper from Table 3 on Figure 1.

The cost of gold is £30 per gram. Calculate the cost of the gold used in the 9 carat gold ring. Use Table 3.

Rings can be made from 22 carat gold. The ratio of the mass of gold in 22 carat gold compared to 9 carat gold is 22 : 9. Calculate the mass of gold in a 22 carat gold ring of mass 5.0 g. Use Table 3.

Calculate the percentage by mass of methanol in methylated spirit. Use Table 6.

The student determined the concentration of sodium chloride in the salt solution using this method: 1. Weigh an empty evaporating dish. 2. Add 25.0 cm³ of the salt solution into the evaporating dish. 3. Heat the evaporating dish and contents. 4. Weigh the evaporating dish and contents. 5. Repeat steps 3 to 4 until there is no further change in mass. 6. Repeat steps 1 to 5 three more times. Why did the student heat the evaporating dish and contents until the mass did not change?

How did the student calculate the mass of solid sodium chloride remaining after steps 1 to 5?

The student calculated the concentration of sodium chloride in the salt solution. Table 1 shows the results. The percentage by mass of sodium ions in sodium chloride is 39.3%. Calculate the mean concentration of sodium ions in the salt solution.

Air is 20% oxygen. Calculate the volume of air needed to provide enough oxygen to react with 3.50 dm³ of hydrogen gas. The equation for the reaction is: 2H₂ + O₂ → 2H₂O

Figure 11 shows the volumes of hydrogen collected in the 50 cm³ measuring cylinder after 40 seconds and after 100 seconds. Determine the number of moles of hydrogen collected between 40 seconds and 100 seconds. The volume of one mole of any gas at room temperature and pressure is 24 dm³.