Answer:
8.9 KJ
Explanation:
Given data:
Mass of strip = 251 g
Initial temperature = 22.8 °C
Final temperature = 75.9 °C
Specific heat capacity of granite = 0.67 j/g.°C
Solution:
Specific heat capacity:
It is the amount of heat required to raise the temperature of one gram of substance by one degree.
Formula:
Q = m.c. ΔT
Q = amount of heat absorbed or released
m = mass of given substance
c = specific heat capacity of substance
ΔT = change in temperature
ΔT = 75.9 °C - 22.8 °C
ΔT = 53.1 °C
Q = 251 g × 0.67 j/g.°C × 53.1 °C
Q = 8929.8 J
Jolue to KJ.
8929.8J ×1 KJ / 1000 J
8.9 KJ
Answer:
Ka = 4.9 X 10^-9
Explanation:
when the pH is 4.95
the [H+] = 10^-4.95
[H+] = 1.122 e-5
since the equilibrium equation is:
HCN <=> 1 mole H+ & 1 mole CN-
then
[H+] = [CN-]
when
HCN <=> H+ & CN-
Ka = [ H+] [CN-] / [HCN]
Ka = [ 1.122 e-5] [ 1.122 e-5] / [0.255]
Ka = 1.256 e-10 / 0.255
Ka = 4.94 e-9
which rounds off to 2 sig figs into
Ka = 4.9 X 10^-9
======================
p.s. it was the pH pf 4.95 that limited the calculations to 2 sig figs
There are 9.8 moles of sodium (Na) in a sample of 5.87 x 10²⁴ atoms of sodium.
<h3>HOW TO CALCULATE NUMBER OF MOLES?</h3>
The number of moles of a substance can be calculated by dividing the number of molecules in the substance by Avogadro's number. That is;
no. of moles = no. of atoms ÷ 6.02 × 10²³
According to this question, there are 5.87 x 10²⁴ atoms of sodium. The number of moles is as follows:
no. of moles = 5.87 x 10²⁴ atoms ÷ 6.02 × 10²³
no. of moles = 0.98 × 10¹
no. of moles = 9.8moles
Therefore, there are 9.8 moles of sodium (Na) in a sample of 5.87 x 10²⁴ atoms of sodium.
Learn more about no. of moles at: brainly.com/question/14919968
Answer:
Mg -atomic number 12
electronic configuration -1s² 2s² 2p^6 3s²
Answer:
Period 4
Explanation:
Given the electronic configuration of the element;
= Is² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p¹
The period of the element is determined by the highest coefficient in the electronic configuration.
For this given configuration (Is² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p¹), "4" is the highest coefficient and the element will certainly belong to period 4 in the periodic table.
To test if the prediction is correct:
Total number of electrons in the given element = 2+2+6+2+6+10+2+1 = 31
The element with atomic number of 31 = Gallium (Ga). (This element belong to period 4).