Answer : The mass of reactant 
remain would be, 0.20 grams.
Solution : Given,
Moles of = 0.40 mol
Moles of 
= 0.15 mol
Molar mass of = 2 g/mole
First we have to calculate the limiting and excess reagent.
The balanced chemical reaction is,
From the balanced reaction we conclude that
As, 1 mole of react with 2 mole of
So, 0.15 moles of react with 
moles of
From this we conclude that, is an excess reagent because the given moles are greater than the required moles and is a limiting reagent and it limits the formation of product.
The moles of reactant remain = 0.40 - 0.30 = 0.10 mole
Now we have to calculate the mass of reactant remain.
Therefore, the mass of reactant remain would be, 0.20 grams.
The answer would be the third one listed, Refraction
Maybe b might be the answer
Concentration is found by dividing the mass of solute by the volume of the solution. C = 4.2g/0.25 L. C= 16.8 g/L
Answer:
The correct option is Ability to store water in leafy structures to prevent excess evaporation.
Explanation:
Desert plants need to have adaptations so that they can withstand the harsh conditions of the environment. In order to withstand the harsh temperatures of the desert, a quiver tree has leafy structures which help it to store water for long time. In this way, water is prevented to be lost from the tree due to evaporation. Hence, it is an effective adaptation to live in desert conditions.
The Quiver tree also has white powder on is branches to hide from the Sun's rays.
