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Greeley [361]
2 years ago
13

A geologist studies layered rock to determine its age. Bacteria fossils from the Precambrian age are found in the rock’s upper l

ayers, but no fossils are found in the rock’s bottom layer. Which of these conclusions about the rock is bet supported by evidence?
Chemistry
1 answer:
kondor19780726 [428]2 years ago
4 0
Answer:
The bottom layers of the rock could have formed before life occurred.

Explanation:
The bottom layers of the rock could have formed before life occurred because there is no fossil is present. If there is life at that time so the fossils are present at the bottom layer so the absence indicates that is no life present at that time. The bottom layer is older than the upper layer so that's why fossils of bacteria are found in the upper layer of the rock.

Answer:
C. Because bacterial fossils are found only in the upper layers, scientists can conclude that these bacteria evolved towards the end of Precambrian time.

There’s two different types of answers for this question so I just put both of them. Hope it helps : )

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Small quantites of hydrogen gas can be prepared in the laboratory by the addition of aqueous hydrochloric acid to metallic zinc.
ira [324]

<u>Answer:</u> The mass or zinc reacted is 0.624 grams.

<u>Explanation:</u>

We are given:

Total pressure = 1.032 atm

Vapor pressure of water = 32 torr = 0.042 atm    (Conversion factor:  1 atm = 760 torr)

To calculate partial pressure of hydrogen gas, we use the equation:

p_{H_2}=p_T-p_{H_2O}\\\\p_{H_2}=1.032-0.042=0.99atm

To calculate the number of moles of hydrogen gas, we use the equation given by ideal gas follows:

PV=nRT

where,

P = pressure of hydrogen gas = 0.99 atm

V = Volume of hydrogen gas = 240. mL = 0.240 L    (Conversion factor: 1 L = 1000 mL)

T = Temperature of hydrogen gas = 30^oC=[30+273]K=303K

R = Gas constant = 0.0821\text{ L. atm }mol^{-1}K^{-1}

n = number of moles of hydrogen gas = ?

Putting values in above equation, we get:

0.99atm\times 0.240L=n\times 0.0821\text{ L atm }mol^{-1}K^{-1}\times 303K\\n=\frac{0.99\times 0.240}{0.0821\times 303}=9.55\times 10^{-3}mol

The chemical equation for the reaction of zinc and hydrochloric acid follows:

Zn+2HCl\rightarrow ZnCl_2+H_2

By Stoichiometry of the reaction:

1 mole of hydrogen gas is produced from 1 mole of zinc metal

So, 9.55\times 10^{-3}mol of hydrogen gas is produced from = \frac{1}{1}\times 9.55\times 10^{-3}=9.55\times 10^{-3}mol of zinc metal

To calculate the mass of zinc metal, we use the equation:

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}

Molar mass of zinc = 65.38 g/mol

Moles of zinc = 9.55\times 10^{-3} moles

Putting values in above equation, we get:

9.55\times 10^{-3}mol=\frac{\text{Mass of zinc}}{65.38g/mol}\\\\\text{Mass of zinc}=(9.55\times 10^{-3}mol\times 65.38g/mol)=0.624g

Hence, the mass or zinc reacted is 0.624 grams.

4 0
3 years ago
A form of energy that is stored in a stretched rubber band is called
storchak [24]
You input potential (stored<span>) </span>energy<span> into the </span>rubber band<span> system when you </span>stretched<span> the</span>rubber band<span> back. Because it is an </span>elastic<span> system, this kind of potential </span>energy<span> is specifically </span>called elastic<span> potential </span>energy<span>. ... When the </span>rubber band<span> is released, the potential </span>energy<span> is quickly converted to kinetic (motion) </span>energy<span>.</span>
6 0
2 years ago
Reactivity occurs when a substance reacts with another substance, changing it into a ____?
MakcuM [25]

Answer:b

Explanation:

6 0
2 years ago
Create a chemical equation for "Bubbling chlorine gas through a solution of sodium bromide gives elemental bromine and a solutio
Alexxandr [17]

Answer:

Cl_{2} +2NaBr ---> 2NaCl + Br_{2}

Explanation:

5 0
2 years ago
The combustion of ethene in the presence of excess oxygen yields carbon dioxide and water: c2h4 (g) + 3o2 (g) → 2co2 (g) + 2h2o
meriva

Answer:

\boxed{-267.5}

Explanation:

You can calculate the entropy change of a reaction by using the standard molar entropies of reactants and products.

The formula is

\Delta_{r} S^{\circ} = \sum_n {nS_{\text{products}}^{\circ} - \sum_{m} {mS_{\text{reactants}}^{\circ}}}

The equation for the reaction is

                        C₂H₄(g) + 3O₂(g) ⟶ 2CO₂(g) + 2H₂O(ℓ)

ΔS°/J·K⁻¹mol⁻¹   219.5      205.0         213.6         69.9

\Delta_{r} S^{\circ} = (2\times213.6 + 2\times69.9) - (1\times219.5 + 3\times205.0)\\\\= 567.0 - 834.5 = \boxed{-267.5 \text{ J}\cdot\text{K}^{-1} \text{mol}^{-1}}

3 0
3 years ago
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