About one kilogram of coffee beans is required
Correct answer: B
Cooling curve is the plot of temperature versus time as the sample is allowed to cool. In a cooling curve, we start at a temperature greater than the boiling point. At this temperature, the sample is in gaseous state. At the boiling point, there is no change in temperature as the gaseous and liquid states are in equilibrium. As the temperature reduces further, the liquid starts to condense and at the melting point of the sample the liquid undergoes phase transition to solid state. At the melting temperature, a second plateau is observed as the temperature remains unchanged. At temperatures below the melting point, the sample exists as a solid.
So from the curve, the second plateau is observed at around -111
. This point represents the phase transition from liquid to solid state.
The two reason behind the invalidity of flame test are false positive and false negative.
while performing the flame test you must have to be accurate otherwise you will get false results may be positive for some element or may be negative in case the element is present. The main reason to get the false positive and false negative is the presence and contamination of sodium.
1) Conversion of an isotope one chemical element or an isotope into another chemical element is called as nuclear transmutation.
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2) In a nuclear transmutation reactions</span> can be achieved either due to radioactive decay or due to nuclear reactions.
3) In this technique, it is possible to convert a stable element into radioactive atom by bombarding in with high speed particles. The initial stable nuclei is referred as parent nuclei, the fast moving particle is referred as projectile while new element which is formed is called as daughter element.
4) In the present reaction:
<span>1 1 H+ 1 0 n -> 2 1 H
1 1H is a parent nuclei which is bombarded with the fast moving projectile
(1 0 n) to generate a new daughter nuclei (2 1H). </span>
