Answer:
In system A: A gas and a solid react to form a new solid product. the system entropy decreases.
In System B: Rubbing alcohol evaporates on the skin. liquid alcohol is converting to gas by evaporation so the system entropy increases.
Explanation:
Entropy is a thermodynamic quantity measure the degree of disorder of a certain system.
Gases have larger entropy compared to liquids which is larger than solids.
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(A) When a gas convert to a solid, its entropy decreases. ... because solids have less energy and entropy than solids.
So, in system A: A gas and a solid react to form a new solid product. the system entropy decreases.
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(B) Any chemical reaction that increases the number of gas molecules also increases entropy.
So, in System B: Rubbing alcohol evaporates on the skin. liquid alcohol is converting to gas by evaporation so the system entropy increases
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The reaction between zinc and hydrogen gas is:
Zn + H₂ → ZnH₂
So for every 1 mole of H₂ gas, it needs 1 mole of Zinc. The atomic weight of H2₂ is 2 g/mol, and Zinc is 67.425 g/mol. The density of H₂ at atmospheric pressure and at 293 K is 0.00016 g/mL. The solution is as follows:
Mass = Density*Volume = (0.00016 g/mL)(150 mL) = 0.024 g H₂
Moles H₂ = 0.024 g H₂ * 1 mol/2 g = 0.012 mol H₂
Thus, it also needs 0.012 mol Zn.
Mass of Zn needed = 0.012 mol * 67.425 g/mol = <em>0.8091 g Zn</em>
Answer:
= 82%
Explanation:
Percentage purity is calculated by the formula;
% purity = (mass of pure chemical/total mass of sample) × 100
In this case;
1 mole of Ca(NO3)2 = 164 g
but; 164 g of Ca(NO3)2 = 40 g Ca
Therefore; mass of Ca(NO3)2 = 164 /40
= 4.1 g
Thus;
% purity of Ca(NO3)2 = (Mass of Ca(NO3)2/ mass of the sample)× 100
= (4.1 g/ 5 g) × 100
= 82%
Answer:
These particles are all called atoms.
Explanation:
Atoms are referred to as the building blocks of all matter. This is because atoms are the smallest pieces that all matter can be broken down into, whether the matter is in a solid, liquid or gaseous state. Atoms combine to form bigger particles called molecules. These molecules are what forms the objects in our surrounding environment. Atoms are comprised of three particles: electrons which have a negative charge, protons which have a positive charge and neutrons which have no charge.