Answer:
D. A chemical reaction
Explanation:
The evolution of a gas and the formation of a new solid with different properties are signs that the original materials have changed into something else.
They have been in a <em>chemical reaction</em>.
A is <em>wrong</em>. Evaporation is a physical change in which the molecules of the liquid move into the gas phase.
B is <em>wrong</em>. Photosynthesis is the use of sunlight by a plant to convert carbon dioxide and water into glucose.
C is <em>wrong.</em> A physical change does not involve a change to another substance with new chemical properties.
yes snow flakes are solid
A) wafting the vapors toward your nose
Answer:
20.11% of oxygen
Explanation:
The reaction is:
2CuO ⇒ 2Cu + O2
If you have an initial amoung of a sample, thi may be have impurities, so you have to start from products to know what you had at the begining.
to make a relation between reagents and products you need to change the mass to mol, then you can relate them with the molar ratio.
Now you have the initial amount of oxygen, to convert to percent you must divide the mass of oxygen between the mass of the sample and multiply by 100
To determine the Ka of the acid, we can use the equation for the pH of weak acids which is expressed as:
pH = -0.5 log Ka
2.67 = -0.5 log Ka
Ka = 4.571x10^-6
Weak acids are acids that do not dissociate completely in solution. The solution would contain the cations, anions and the acid itself as a compound. Hope this helps.
