Fractional crystallization
Fractional distillation
Filtration
Evaporation
Correct answer is A
No explanation has been provided for this answer.
Which of the following does not support the fact that air is a mixture?
the constituents of air are in a fixed proportion by mass
it cannot be represented with a chemical formula
the constituents of air can be separated by physical by physical means
none of the above
Correct answer is D
No explanation has been provided for this answer.
Which of the following statements about catalyst is false?
biological catalysts are called enzymes
catalyst do not appear in the balanced equation
catalyst reduce the activation energy for a reaction
catalysts do not alter the mechanism of the reaction and never appear in the rate low
Correct answer is D
No explanation has been provided for this answer.
-122kJ
-132kJ
-88kJ
-60kJ
Correct answer is B
No explanation has been provided for this answer.
yellow to green
orange to green
yellow to red
orange to red
Correct answer is B
Potassium dichromate is an oxidising agent in organic chemistry. It is used to oxidize alcohols.
In an aqueous solution the color change exhibited can be used to test for distinguishing aldehydes from ketones. Aldehydes reduce dichromate from the +6 to the +3 oxidation state, changing color from orange to green. This color change arises because the aldehyde can be oxidized to the corresponding carboxylic acid.