Answer: 5
Explanation: add up all the electrons and it will amount to 23. Arranging by the old model for electronic configuration, we have : 2, 8, 8, 5
The last number being 5 represent its valence electron
<u>Given:</u>
Mass of MgBr2 = 0.500 g
<u>To determine:</u>
Number of anions in 0.500 g MgBr2
<u>Explanation:</u>
Molar mass of MgBr2 = 24 + 2 (80) = 184 g/mol
Moles of MgBr2 = 0.500 g/184 g.mol-1 = 0.00271 moles
Based on stoichiometry-
1 mole of MgBr2 has 1 mole of Mg2+ cations and 2 moles of Br- anions
Therefore, 0.00271 moles of MgBr2 will have: 2 * 0.00271 = 0.00542 moles of Br-
Now,
1 mole of Br- contains 6.023 * 10²³ anions
0.00542 moles of Br- contain: 0.00542 * 6.023*10²³ = 3.264*10²¹ anions
Ans: There are 3.264*10²¹ anions in 0.5 g of MgBr2
Can’t have anything in Detroit
Answer:
Heat given off was -34.34kJ
Explanation:
Mass of iron bar = 869g
Initial temperature (T1) = 94°C
Final temperature (T2) = 5°C
Specific heat capacity of iron (c) = 0.444J/g°C
Heat energy (Q) = Mc∇T
Q = heat energy
c = specific heat capacity
∇T = change in temperature
M = mass of the substance
Q = mc∇T
∇T = T2 - T1
Q = Mc(T2 -T1)
Q = 869 * 0.444 * (5 - 94)
Q = 385.836 * -89
Q = -34339.404J
Q = -34.34kJ
The heat given of was -34.34kJ
Second one i think.......
