Hich of the following properties of an unknown substance would allow it to be classified as a pure substance? The unknown substance –

is not able to conduct any electric current.

has an overall density greater than that of water.

consists of a solid dissolved in distilled water.

is composed throughout of one and only one element.

The drawing represents the movement of particles in a substance. what changes of state can this substance undergo

The scheme below is from a series of reactions that are part of a synthesis of vitamin a. answer the following questions with reference to this scheme. (i) what is "reagent a"? (ii) draw a step-by-step mechanism which explains the formation of compound c from compound b (iii) which reagents would you use to form compound e from compounds c and d (reagents b and c)? for each reagent suggested above in (ii) explain the role of the reagent in the reaction to (iv) form compound e. you may wish to do this by drawing a mechanism. 1. addition of reagent a но reagent a 2. н,о" thо oh нон-с compound a. compound b. compound c .ch-оh 1. reagent b "сно 2. reagent c сh oh compound e. compound d.

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