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jasenka [17]
3 years ago
12

The oldest fossils and evidence of modern humans on earth are around 200,000 years old. Before that time lived the ancestors of

modern humans and Neanderthals. If all of earth’s history was compressed into 12 hours, what time would you first see modern humans?
Chemistry
2 answers:
Serggg [28]3 years ago
3 0

Answer:

I would say around the 11th or 12th hour

Explanation:

seeing as the question calls for ALL of earth's history compressed into 12 hours the timeline should be similar to this: Earth was born at midnight, at around 2-3 AM land masses form, Right after that, life begins, For around 8 hours (11 PM) life is confined in water, right after that we have plants, 22 minutes later we have dinosaurs, 22 minutes later we have mammals, 5 minutes later dinosaurs are extinct, 6 minutes later we have people. So it's most likely the 12th hour. I hope this helps.

const2013 [10]3 years ago
3 0
You would see modern humans in the last hour, specifically possibly closer to the last couple of minutes if the earth really is as old as scientists predict
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Given the balanced equation representing a reaction:
Nesterboy [21]

Answer:

It accepted a proton from HCl

Explanation:

When properly written, the equation box the reaction is given as; HCl(aq) + H2O(l) ----> H3O+(aq) + Cl-(aq).

According to Brownstead-Lowry definition of acids and bases, an acid donates protons while a base accepts protons.

Water molecule acts as a base in the reaction because it accepted a proton from HCl in the reaction above.

7 0
3 years ago
The author of Space Systems: All About Eclipses makes the point that seeing a total solar eclipse is rare. How does the author u
Ilia_Sergeevich [38]

Answer:

<h3>A.</h3>

Explanation:

If A does not work, please use the alteritive choice, which is D!

が機能しない場合は、別の選択肢であるDを使用してください。 ^ 3 ^

3 0
2 years ago
It is necessary to know the time of day and the position of the Sun or the stars relative to one's longitude line because ____.
allochka39001 [22]

Answer: the longitude line rotates with Earth, 360 degrees in 24 hours.

Explanation: In the old days, the position of the sun was used to tell which time of the day it is. But more modern findings, has shown that the longitude line matters too.

3 0
3 years ago
Analysis of a gaseous chlorofluorocarbon, CClxFy, shows that it contains 11.79% C and 69.57% Cl. In another experiment, you find
uranmaximum [27]

Answer:

The molecular formula = C_2Cl_{4}F_2

Explanation:

Moles =\frac {Given\ mass}{Molar\ mass}

% of C = 11.79

Molar mass of C = 12.0107 g/mol

<u>% moles of C = 11.79 / 12.0107 = 0.9816</u>

% of Cl = 69.57

Molar mass of Cl = 35.453 g/mol

<u>% moles of Cl = 69.57 / 35.453 = 1.9623</u>

Given that the gaseous chlorofluorocarbon only contains chlorine, flourine and carbon. So,

% of F = 100% - % of C - % of C = 100 - 11.79 - 69.57 = 18.64

Molar mass of F = 18.998 g/mol

<u>% moles of F = 18.64 / 18.998 = 0.9812</u>

Taking the simplest ratio for C, Cl and F as:

0.9816 : 1.9623 : 0.9812

= 1 : 2 : 1

The empirical formula is = CCl_2F

Also, Given that:

Pressure = 21.3 mm Hg

Also, P (mm Hg) = P (atm) / 760

Pressure = 21.3 / 760 = 0.02803 atm

Temperature = 25 °C

The conversion of T( °C) to T(K) is shown below:

T(K) = T( °C) + 273.15  

So,  

T = (25 + 273.15) K = 298.15 K  

Volume = 458 mL  = 0.458 L (1 mL = 0.001 L)

Using ideal gas equation as:

PV=nRT

where,  

P is the pressure

V is the volume

n is the number of moles

T is the temperature  

R is Gas constant having value = 0.0821 L.atm/K.mol

Applying the equation as:

0.02803 atm × 0.458 L = n × 0.0821 L.atm/K.mol × 298.15 K  

⇒n = 0.00052445 moles

Given that :  

Amount  = 0.107 g  

Molar mass = ?

The formula for the calculation of moles is shown below:

moles = \frac{Mass\ taken}{Molar\ mass}

Thus,

0.00052445= \frac{0.107\ g}{Molar\ mass}

Molar\ mass= 204.0233\ g/mol

Molecular formulas is the actual number of atoms of each element in the compound while empirical formulas is the simplest or reduced ratio of the elements in the compound.

Thus,  

Molecular mass = n × Empirical mass

Where, n is any positive number from 1, 2, 3...

Mass from the Empirical formula = 1×12.0107 + 2×35.453 + 1×18.998 = 101.9147 g/mol

Molar mass = 204.0233 g/mol

So,  

Molecular mass = n × Empirical mass

204.0233 = n × 101.9147

⇒ n = 2

<u>The molecular formula = C_2Cl_{4}F_2</u>

6 0
3 years ago
What is the engine piston displacement in liters of an engine whose displacement is listed as 490 in^3?
marishachu [46]

Answer:

490 in^3 = 8.03 L

Explanation:

Given:

The engine displacement = 490 in^3

= 490 in³

To determine the engine piston displacement in liters L;

(NOTE: Both in^3 (in³) and L are units of volume). Hence, to find the engine piston displacement in liters (L), we will convert in^3 to liters (L)

First, we will convert in³ to cm³

Since 1 in = 2.54 cm

∴ 1 in³ = 16.387 cm³

If 1 in³ = 16.387 cm³

Then 490 in³ =  (490 in³ × 16.387 cm³) / 1 in³ = 8029.63 cm³

∴ 490 in³ = 8029.63 cm³

Now will convert cm³ to dm³

(NOTE: 1 L = 1 dm³)

1 cm = 1 × 10⁻² m = 1 × 10⁻¹ dm

∴ 1 cm³ = 1 × 10⁻⁶ m³ = 1 × 10⁻³ dm³

If 1 cm³ = 1 × 10⁻³ dm³

Then, 8029.63 cm³ = (8029.63 cm³ × 1 × 10⁻³ dm³) / 1 cm³ = 8.02963 dm³

≅ 8.03 dm³

∴ 8029.63 cm³ = 8.03 dm³

Hence, 490 in³ = 8029.63 cm³ = 8.03 dm³

Since 1L = 1 dm³

∴ 8.03 dm³ = 8.03 L

Hence, 490 in³ = 8.03 L

3 0
2 years ago
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