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LekaFEV [45]
2 years ago
7

How many molecules are in 55.2g of MgBr2

Chemistry
1 answer:
Umnica [9.8K]2 years ago
8 0

Answer:

Divide the given mass by its molar mass to get moles, then multiply times 6.022×1023 molecules 1 mol .

Converting between molecules and moles is done by either multiplying by or dividing by Avogadro's number:

1.To go from moles to molecules, multiply the number of moles by 6.02 x 1023.

2.To go from molecules to moles, divide the numbers of molecules by 6.02 x 1023.

We know that the number of moles is equal to the weight of the substance divided by its molar mass. Therefore, the number of moles in 19.82g of Mg is 0.81 mol.

Explanation:

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The energy release when dissolving 1 mol of NaOH in water is 445.1 kJ
the mass of NaOH to be dissolved is 32.0 g
The number of NaOH moles in 32.0 g - 32.0 g / 40 g/mol =  0.8 mol
the energy released whilst dissolving 1 mol of NaOH - 445.1 kJ
when dissolving 0.8 mol - the energy released is 445.1 kJ/mol x 0.8 mol
therefore heat released is - 356.08 kJ
answer is -356.08 kJ
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Explanation:

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The half-life for the radioactive decay of C-14C-14 is 5730 years. You may want to reference (Pages 598 - 605) Section 14.5 whil
KIM [24]

<u>Answer:</u> The sample of Carbon-14 isotope will take 2377.9 years to decay it to 25 %

<u>Explanation:</u>

The equation used to calculate rate constant from given half life for first order kinetics:

t_{1/2}=\frac{0.693}{k}

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t_{1/2} = half life of the reaction = 5730 years

Putting values in above equation, we get:

k=\frac{0.693}{5730yrs}=1.21\times 10^{-4}yrs^{-1}

Rate law expression for first order kinetics is given by the equation:

k=\frac{2.303}{t}\log\frac{[A_o]}{[A]}

where,

k = rate constant  = 1.21\times 10^{-4}yr^{-1}

t = time taken for decay process = ? yr

[A_o] = initial amount of the sample = 100 grams

[A] = amount left after decay process =  (100 - 25) = 75 grams

Putting values in above equation, we get:

1.21\times 10^{-4}=\frac{2.303}{t}\log\frac{100}{75}\\\\t=2377.9yrs

Hence, the sample of Carbon-14 isotope will take 2377.9 years to decay it to 25 %

8 0
3 years ago
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