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timofeeve [1]
2 years ago
12

How many grams of CaH2CaH2 are needed to generate 147 LL of H2H2 gas if the pressure of H2H2 is 823 torrtorr at 21 ∘C∘C? Express

your answer using three significant figures.
Chemistry
1 answer:
My name is Ann [436]2 years ago
8 0

Answer:

139 g of CaH₂ were needed in the reaction

Explanation:

Determine the reaction:

CaH₂ + 2H₂O  →  Ca(OH)₂  +  2H₂

1 mol of calcium hidride reacts with 2 moles of water to produce 1 mol of calcium hydroxide and 2 moles of hydrogen

Let's determine the moles of formed hydrogen by the Ideal Gases Law

P . V = n . R . T

P = 823 Torr . 1 atm/760 Torr = 1.08 atm

T = Absolute T° → T°C + 273 → 21°C + 273 = 294K

1.08 atm . 147 L = n . 0.082 . 294K

(1.08 atm . 147 L) / (0.082 . 294K) = n → 6.60 moles

Ratio is 2:1. We make a rule of three:

2 moles of H₂ came from 1 mol of hydride

Then 6.60 moles of H₂ must came from 3.30 moles of hydride (6.60 .1) /2

Let's convert the moles to mass →  3.30 mol . 42.08 g/ 1 mol =

138.8 g ≅ 139 g

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Archeologists can determine the age of artifacts made of wood or bone by measuring the amount of the radioactive isotope 14C pre
Ahat [919]

Answer: The age of the tool is 15539 years

Explanation:

Expression for rate law for first order kinetics is given by:

t=\frac{2.303}{k}\log\frac{a}{a-x}

where,

k = rate constant  

t = age of sample

a = let initial amount of the reactant = 100

a - x = amount left after decay process = \frac{15.5}{100}\times 100=15.5  

a) for completion of half life:

Half life is the amount of time taken by a radioactive material to decay to half of its original value.  

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

k=\frac{0.693}{5730yr}=0.00012yr^{-1}

b) for 15.5 % of original amount

t=\frac{2.303}{0.00012}\log\frac{100}{15.5}

t=15539years

Thus age of the tool is 15539 years

8 0
3 years ago
Sulfur and oxygen form both sulfur dioxide and sulfur trioxide. When samples of these were decomposed the sulfur dioxide produce
Zinaida [17]

Answer : The mass of oxygen per gram of sulfur for sulfur dioxide and sulfur trioxide is, 0.997 g and 1.5 g respectively.

Explanation : Given,

Mass of oxygen in sulfur dioxide = 3.49 g

Mass of sulfur in sulfur dioxide = 3.50 g

Mass of oxygen in sulfur trioxide = 9.00 g

Mass of sulfur in sulfur trioxide = 6.00 g

Now we have to calculate the mass of oxygen per gram of sulfur for sulfur dioxide and sulfur trioxide.

Mass of oxygen per gram of sulfur for sulfur dioxide = \frac{\text{Mass of oxygen}}{\text{Mass of sulfur}}

Mass of oxygen per gram of sulfur for sulfur dioxide = \frac{3.49}{3.50}=0.997g

and,

Mass of oxygen per gram of sulfur for sulfur trioxide = \frac{\text{Mass of oxygen}}{\text{Mass of sulfur}}

Mass of oxygen per gram of sulfur for sulfur trioxide = \frac{9.00}{6.00}=1.5g

Thus, the mass of oxygen per gram of sulfur for sulfur dioxide and sulfur trioxide is, 0.997 g and 1.5 g respectively.

8 0
3 years ago
Can a solution with undissolved solute be supersaturated
Helen [10]

Answer: A supersaturated solution will not contain undissolved solute because the undissolved solute will be indicative of saturated solution.

Explanation:

A supersaturated solution is the one that consists of more than the maximum concentration of the solute in the solvent that is being dissolved at a given temperature. A saturated solution is the one in which the maximum concentration of solute has been dissolved in the solvent and no additional solute can be dissolved further.

According to the given statement, a solution with undissolved solute is a saturated solution rather a supersaturated solution.

5 0
3 years ago
Write this number in scientific notation: 0.000467?
Troyanec [42]

Answer:

Explanation:

scientific notation of 0.000467 is

  4.67*10^-4

3 0
3 years ago
Salt seems to dissappear when it is poured into water. Use mixture, solution, and dissolve to explain what happens.
fgiga [73]
The salt desolves into the water which forms a solution which is called a mixture.
8 0
3 years ago
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