Answer:
19. Option B. ⁰₋₁B
20. Option D. ²¹⁰₈₄Po
Explanation:
19. ²²⁸₈₈Ra —> ²²⁸₈₉Ac + ʸₓZ
Thus, we can determine ʸₓZ as follow:
228 = 228 + y
Collect like terms
228 – 228 = y
y = 0
88 = 89 + x
Collect like terms
88 – 89 = x
x = –1
Thus,
ʸ ₓZ => ⁰₋₁Z => ⁰₋₁B
²²⁸₈₈Ra —> ²²⁸₈₉Ac + ʸₓZ
²²⁸₈₈Ra —> ²²⁸₈₉Ac + ⁰₋₁B
20. ᵘᵥX —> ²⁰⁶₈₂Pb + ⁴₂He
Thus, we can determine ᵘᵥX as follow:
u = 206 + 4
u = 210
v = 82 + 2
v = 84
Thus,
ᵘᵥX => ²¹⁰₈₄X => ²¹⁰₈₄Po
ᵘᵥX —> ²⁰⁶₈₂Pb + ⁴₂He
²¹⁰₈₄Po —> ²⁰⁶₈₂Pb + ⁴₂He
Answer:
Open spaces in water's solid structure makes its solid state less dense than its liquid state.
Explanation:
- Water unlike other liquids is special. It contracts when cooled, down to a temperature of 4°C but thereafter begins to expand as it reaches 0°C and turns into ice.
- This property is useful for the preservation of marine life in very cold temperatures. During winter, the surface water in water lakes and rivers starts cooling. Upon reaching the temperature of 4°C, the surface water descends to the bottom as it denser.
- This help in the maintenance of temperature of the water at the bottom at 4°C. It is in this layer that marine life is sustained.
Moles of X are 0.925 moles.
A mole is a totally vital unit of dimension that chemists use.The mole, symbol mol, is the unit of amount of substance inside the worldwide device of gadgets. the amount quantity of the substance is a measure of how many simple entities of a given substance are in an item or sample. The mole is described as containing exactly 6.02214076×10²³ primary entities
mass of X2O3 = 4 g
so moles = mass/molar mass
molar mass of X2O3 = 2*X + 48 -
Given, that the mass of X = 2.8g
mass of O = 4 - 2.8 = 1.2g
A mole of O = 1.2g/16 = 0.075 mole
∴ mole of X = 1 - 0.075 = 0.925 moles.
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