The answers is A. Reales energy stored in chemical bonds
Answer: C) Non-metals can share pairs of electrons and form covalent bonds
Explanation: The principal reason why it is non-metals that can form covalent bonds is because of their electronegativities. Electronegativity is the tendency of an atom to attract electrons towards itself.
The participating atoms in a covalent bond have to be able to hold the shared electron in place & it is this attraction towards the centre of each participating atom that holds the electrons in place. Metals aren't electronegative, they don't attract electrons towards each other, they'd rather even push the electrons away from themselves (electropositive) to be stable. The closest concept of metals to shared electrons is in metallic bonding, where metals push and donate their valence electrons to an electron cloud which is free to move around the bulk of the metallic structure. But this is nowhere near the type of bonding that exist in covalent bonds.
Earth contains huge quantities of water in its oceans, lakes, rivers, the atmosphere, and believe it or not, in the rocks of the inner Earth. Over millions of years, much of this water is recycled between the inner Earth, the oceans and rivers, and the atmosphere. This cycling process means that freshwater is constantly made available to Earth's surface where we all live. Our planet is also very efficient at keeping this water. Water, as a vapor in our atmosphere, could potentially escape into space from Earth. But the water doesn't escape because certain regions of the atmosphere are extremely cold. (At an altitude of 15 kilometers, for example, the temperature of the atmosphere is as low as -60° Celsius!) At this frigid temperature, water forms solid crystals that fall back to Earth's surface.
Many people live faraway from freshwater sources. They need to carry their water home.
While our planet as a whole may never run out of water, it's important to remember that clean freshwater is not always available where and when humans need it. In fact, half of the world's freshwater can be found in only six countries. More than a billion people live without enough safe, clean water.
Also, every drop of water that we use continues through the water cycle. Stuff we put down the drain ends up in someone or something else's water. We can help protect the quality of our planet's freshwater by using it more wisely.
Answer: D. 19.9 g hydrogen remains.
Explanation:
To calculate the moles, we use the equation:
a) moles of 
b) moles of 
According to stoichiometry :
1 mole of require 1 mole of
Thus 0.0787 moles of 
require=
of
Thus is the limiting reagent as it limits the formation of product and acts as the excess reagent. (10.0-0.0787)= 9.92 moles of are left unreacted.
Mass of 
Thus 19.9 g of remains unreacted.
Can you please tell me what the procedures are
