When large pieces of a purple-black crystalline solid are gently heated, a purple vapor is formed which upon cooling deposits many tiny purple-black crystals with the same hardness, density, reflectivity, etc. as the large pieces.  Did this experiment study chemical changes or physical ones?  Justify your answer with reasoning.

Large amounts of titanium metal are refined by reacting titanium(III) chloride solution with magnesium metal. To test this refining process, a student reacts 1.55 kg of magnesium metal with excess titanium(III) chloride solution. After the reaction was complete, the student had extracted 1.62 kg of titanium metal. From this data, calculate the percent error of this experiment. Hint: Write a balanced chemical reaction equation and calculate theoretical mass first. Do not show your work in the space provided. Record only your final answer with the correct number of significant digits and the proper units. Answer: Evaluate your calculated percent error. Is this an acceptable percent error?

Examine the equations in the first column. Name two things the have in common.

Write a balanced chemical equation for each of the following. Express your answer as a chemical equation. Identify all of the phases in your answer.  Gaseous butane (C4H10) reacts with oxygen gas to form carbon dioxide gas and water vapor.    Liquid methanol (CH3OH) reacts with oxygen gas to form carbon dioxide gas and water vapor.

1. A student overheats their beaker during the dehydration of the copper salt, creating black CuO(s) and Cl2 (g). How will this error change the mass of water calculated? Explain. 2. A student overheats their beaker during the dehydration of the copper salt, creating black CuO(s) and Cl2 (g). How will this error change the mass of copper calculated? Explain. You may assume that the student is able to react all of the CuO with the aluminum wire. 3. A student reports an erroneously-high waters of hydration mass but the correct copper mass for their sample. How will this change the mass of chloride calculated? Explain.

A student finds that 24.96 g of water at 24.9 C(density=0.9971 g/cm3) is required to completly fill an empty flask. The water is removed and completely dried; granular solid copper weighing 51.24g is then added to the flask. With the copper present in the flask, it was determined that 19.24 g of water was required to fill the remaining space in the flask completly 1.) volume of the empty flask 2.) volume of the copper  3.) density of the copper

How can you distinguish an element, from a compound, from a solution, from a heterogeneous mixture? Explain

A standard curve for absorbance vs. concentration has an equation of y = 2.0x.  If an unknown compound has an absorbance of 0.856, what is its concentration? Units not required. Report your answer to the correct number of significant figures.

In a lab students tested two properties of four substances. The results of the tests are shown the table below. Substance Phase at room Reaction with Reaction to flame temperature water Hydrogen Colorless Gas None Explodes Potassium Silver Solid Bubbling and reaction is hot. Burns and is likely to explode Sulfur Yellow Solid None Burns slowly and turns a color Strontium chloride White Crystalline Solid Dissolves Melts Which substance and explanation proves that no chemical change took place? O A. Hydrogen because it did not react with water and will explode when exposed to a flame. O B. Potassium because it bubbles in water and will explode when exposed to a flame Type here to search

A student reacts 1.53 kg of magnesium metal with excess titanium(III) chloride solution. After the reaction was complete, the student had extracted 1.62 kg of titanium metal. From this data, calculate the percent error of this experiment.