Anwer question for 20 points
a group of chemistry students had to identify six white powders. the students used a variety of tests to identify the powders. they computed the density of each powder. they checked to see if any dissolved in water. one of the powders did not dissolve in water and they thought it was cornstarch. someone knew that cornstarch felt slippery and reacted with iodine. the students put a few drops of iodine on each white powder. one powder turned black; they guessed that it was cornstarch. they heated the powders in a bunsen burner flame to see if any would melt. one did and they guessed it might be a sugar.

which test result indicated a chemical change had taken place?

a)
dissolves in water

b)
feels slippery in water

c)
melts when heated in a flame

d)
turns black when iodine is added

1. how much energy is needed to raise the temperature of 40.0 g of argon from 25c to 40c? the specific heat capacity of argon is 0.520 j/(g·k) 2a. 23.0 ml of 0.100 m hcl (standard) are added from a buret to neutralize 50.0 ml of an unknown basic solution. 2b. if the oh- produced in the previous reaction came from ca(oh)2, then what is the molarity of the ca(oh)2? 3.calculate the new freezing-point of a solution when 60.5 grams of cacl2 solute is dissolved in 0.612 kg of water. 4. what is the maximum number of moles of alcl3 that can be produced from 5.0 mol al and 6.0 mol cl2? 5. a sample of oxygen gas has a volume of 150 ml when its pressure is 0.923 atm. if the pressure is increased to 0.987 atm and the temperature remains constant, what will the new volume be? 6. nitrogen gas in a closed container at a temperature of 100.0 oc and 3.0 atm is heated to 300 oc. what is the pressure of the gas at the higher temperature?