If 300 g of water at 25°C is mixed with 200 g of water at 75°C, what is the fina

Practice Questions

Q1
If 300 g of water at 25°C is mixed with 200 g of water at 75°C, what is the final temperature? (Specific heat of water = 4.2 J/g°C)
  1. 40°C
  2. 50°C
  3. 60°C
  4. 70°C

Questions & Step-by-Step Solutions

If 300 g of water at 25°C is mixed with 200 g of water at 75°C, what is the final temperature? (Specific heat of water = 4.2 J/g°C)
  • Step 1: Identify the masses and temperatures of the two water samples. We have 300 g of water at 25°C (m1 = 300 g, T1 = 25°C) and 200 g of water at 75°C (m2 = 200 g, T2 = 75°C).
  • Step 2: Write down the formula to find the final temperature (Tf) when two masses of water are mixed: m1*T1 + m2*T2 = (m1 + m2)*Tf.
  • Step 3: Substitute the values into the formula: 300*25 + 200*75 = (300 + 200)*Tf.
  • Step 4: Calculate the left side: 300*25 = 7500 and 200*75 = 15000. So, 7500 + 15000 = 22500.
  • Step 5: Calculate the total mass: 300 + 200 = 500 g.
  • Step 6: Now we have the equation: 22500 = 500*Tf.
  • Step 7: To find Tf, divide both sides by 500: Tf = 22500 / 500.
  • Step 8: Calculate Tf: 22500 / 500 = 45°C.
  • Heat Transfer – The principle of conservation of energy where the heat lost by the hotter water equals the heat gained by the cooler water.
  • Specific Heat Capacity – Understanding that specific heat capacity is a measure of how much heat energy is required to change the temperature of a substance.
  • Weighted Average – Calculating the final temperature as a weighted average based on the masses and initial temperatures of the two water samples.
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