Answer:
C) Potassium, K, and calcium, Ca
Explanation:
Given pair of elements:
Ni and Cu
Potassium and Ca
Nitrogen and oxygen
Solution:
We know that number of protons and number of electrons are always equal and number of electron or number of proton is called atomic number.
Number of protons given elements:
Ni number of protons = 28
Copper number of protons = 29
Combine number of protons = 57
K number of protons = 19
Ca number of protons = 20
Combine number of protons = 39
Ni number of protons = 7
O number of protons = 8
Combine number of protons = 15
Thus, option C is correct.
Answer:
1.52g NaHCO3 were in the original mixture.
Mass percent: 64.1%
Explanation:
When NaHCO3 heats it descomposition occurs as follows:
2 NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g).
The loss in mass is because of the evaporization of CO2 and H2O. As both are in the same porportion, its molar mass is the sum of both compounds (44g/mol + 18g/mol = 62g/mol)
Loss in mass: 74.80g - 74.24g = 0.56g.
In moles:
0.56g * (1mol / 62g) = 0.00903 moles of gas.
As 1 mole of the gases comes from 2 moles of NaHCO3:
<em>Moles NaHCO3:</em>
0.00903 moles of gas * (2 moles NaHCO3 / 1 mole gas) = 0.018 moles NaHCO3.
In grams (Molar mass NaHCO3: 84g/mol):
0.018 moles NaHCO3 * (84g / mol) = 1.52g NaHCO3 were in the original mixture.
The mass of the mixture was:
74.80g - 72.428g = 2.372g
That means mass percent of NaHCO3 is:
(1.52g / 2.372g) * 100 = 64.1%
True becuase the substance changed into another substance which is a example of a chemical reaction.
Answer:
8 kg mass
Explanation:
As we can see in the image the weight of mass 8 kgs has a large surface area as compared to the surface area of other masses. In general, it has been observed that a wide surface area has more surface particle for heat conduction. Hence, the rate of heat transfer is directly proportional to the surface area of heat conducting surface. Thus, the larger the surface area, the faster is the rate of heat conduction.
Hence, weight of mass 8Kg wil transfer heat a fast rate.
<span>More surface area --> more molecules of the solute in contact with the solvent --> more chance for a solvent molecule to collide with the solute molecules --> dissolves faster
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