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Questions in chemistry

📝 Answered - How many grams of calcium bromide are in 50.0 mL of a 0.25 M calcium bromide solution?

📝 Answered - What is the evidence of a chemical reaction when fireworks go off?

📝 Answered - Particles are arranged in a crystal structure in a sample of: A. \(\text{H}_2\) (g) B. \(\text{Br}_2\) (l) C. \(\text{Ar}\) (g) D. \(\text{Ag}\) (s)

📝 Answered - List four physical properties of each of the following: 1. A piece of copper wire 2. 500g of butter 3. A glass of milk 4. A candle 5. A piece of aluminum foil 6. A spoonful of sugar 7. Toothpaste

📝 Answered - Decode the following message using the atomic number plus the highest principal quantum number: 5, 30, 58, 56, 99, 79, 19, 98, 9

📝 Answered - The standard molar heat of vaporization for water is 40.79 kJ/mol. How much energy would be required to vaporize 30.0 g of water? Answer in units of kJ.

📝 Answered - What is "plastic" rock and how does it move?

📝 Answered - Which processes of the water cycle occur by releasing energy?

📝 Answered - If it takes one second to count two rice grains, calculate the time in years required to count a mole of rice grains.

📝 Answered - Lee conducts an experiment to see if mass is conserved when a piece of charcoal is burned for 5.0 minutes. He measures the mass of the charcoal before lighting it with a match. At the end of 5.0 minutes, Lee puts out the fire by suffocating it. After the charcoal has cooled, he measures its mass again. His data are below: | Initial Mass | Final Mass | |--------------|------------| | 0.415 g | 0.289 g | Charlene tries to repeat Lee's experiment by using a different piece of charcoal. But she burns the charcoal for just 3.0 minutes and collects all of the gas and dust released by the burning charcoal. She then weighs the total mass of these objects. Her results are below: | Initial Mass | Final Mass | |--------------|------------| | 0.498 g | 0.498 g | Charlene's experimental results indicate that mass was conserved. Why do Lee's results indicate that mass was not conserved? A. He burned the charcoal for a longer period of time than Charlene did. B. He did not collect the gas and dust released by the burning charcoal. C. He forgot to measure the mass of the charcoal while it was still burning. D. Mass is not conserved when an object undergoes a chemical change.