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These 10 problems cover key concepts you know. Take your time, show your work, and believe in yourself!
Instructions
Complete all problems showing your work. Use proper significant figures and include units with every step. Remember: you know this material!
Problem 1
Round 3458.23 to 2 significant figures.
Problem 2
Convert 2.5 kg to grams.
Problem 3
Convert 45,000 cm to km.
Problem 4
A car travels 120 miles in 2.0 hours. Convert this speed to kilometers per minute. (1 mile = 1.609 km)
Problem 5
A fruit smoothie contains 15% strawberries by volume. If you make a 500 mL smoothie, how many mL of strawberries are in it?
Problem 6
A brass doorknob has a mass of 280 g and is 70% copper. How many ounces of copper does the doorknob contain? (1 oz = 28.35 g)
Problem 7
Calculate the molar mass of sodium hydroxide (NaOH). (Na = 22.99 g/mol, O = 16.00 g/mol, H = 1.01 g/mol)
Problem 8
Calculate the molar mass of table sugar, sucrose (C₁₂H₂₂O₁₁). (C = 12.01 g/mol, H = 1.01 g/mol, O = 16.00 g/mol)
Problem 9
A 50.0 g piece of aluminum is heated from 25.0°C to 75.0°C. How much heat energy was absorbed? (Specific heat of aluminum = 0.900 J/g°C)
Problem 10
A student has 25.0 grams of table salt (NaCl) and needs to calculate how many moles this represents. The molar mass of NaCl is 58.44 g/mol. How many moles of NaCl does the student have?
Problem 11
A hot piece of unknown metal is placed in cool water and causes the water level to rise. Use the data tables below to:
- Calculate the experimental specific heat of the metal
- Calculate the experimental density of the metal
- Identify which metal it is from the reference table
- Calculate the percent error for both specific heat and density
Experimental Data:
| Substance | Mass | Initial Temp | Final Temp |
|---|---|---|---|
| Metal | 45.0 g | 95.0°C | 28.5°C |
| Water | 100.0 g | 22.0°C | 28.5°C |
Volume Displacement Data:
| Measurement | Volume Reading |
|---|---|
| Initial water level | 50.0 mL |
| Water + metal | 56.7 mL |
Reference Table - Possible Metals:
| Metal | Specific Heat (J/g°C) | Density (g/cm³) |
|---|---|---|
| Aluminum | 0.900 | 2.70 |
| Copper | 0.385 | 8.96 |
| Iron | 0.85 | 7.87 |
Hints: Heat lost by metal = Heat gained by water; Density = mass/volume; Percent error = |(experimental - accepted)/accepted| × 100%; Specific heat of water = 4.18 J/g°C; Note: Density is usually a more reliable property than specific heat for identifying metals in simple laboratory experiments.