Answer:
B and C
Explanation:
When we have to do a buffer solution we always have to choose the reaction that has the <u>pKa closer to the desired pH value</u>. When we find the pKa values we will obtain:
![pKa_1=-Log[6.9x10^-^3]=2.16](https://tex.z-dn.net/?f=pKa_1%3D-Log%5B6.9x10%5E-%5E3%5D%3D2.16)
![pKa_2=-Log[6.2x10^-^8]=7.20](https://tex.z-dn.net/?f=pKa_2%3D-Log%5B6.2x10%5E-%5E8%5D%3D7.20)
![pKa_3=-Log[4.8x10^-^13]=12.31](https://tex.z-dn.net/?f=pKa_3%3D-Log%5B4.8x10%5E-%5E13%5D%3D12.31)
The closer value is pKa2 with a value of 7.2. Therefore we have to use the second reaction. In which 
is the <u>acid</u> and 
is the <u>base</u>. Therefore the answer for the first question is B and the answer for the second question is C.
Gravity is a force which tries to pull two objects toward each other. Anything which has mass also has a gravitational pull. The more massive an object is, the stronger its gravitational pull is. Earth's gravity is what keeps you on the ground and what causes objects to fall.
The image represents A COMPOUND because the molecules are BONDED CHEMICALLY.
A compound is a substance formed when two or more elements combine together chemically. In the process of chemical combination, the chemical bonds that were present in the participating elements will be broken and new chemical bonds will be formed in the product.
Atomic number is 8 and atomic mass is taken as 16 amu
Answer:
Explanation:
Scientists know that there are 6x1023 molecules in a mole - so we have about 0.5x1023 molecules in our marble…and since every silicon dioxide molecule has one atom of silicon and two of oxygen, we have a grand total of 1.5x1023 atoms. That's 150,000,000,000,000,000,000,000 atoms
