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3 years ago

1. What is the geologic time scale? Explain how the geologic time scale is a model.

Chemistry

2 answers:

oksano4ka [1.4K]3 years ago

6 0

This is the answer hope it will help you

tiny-mole [99]3 years ago

5 0

1.) the geologic time scale is a system of chronological dating that relates geologic structure to geologic events. it is a model because it measures and describes events and relationships in geologic history.

2.) the paleozoic period was roughly from 245 million years ago to 545 million years ago.

3.) the dinosaurs lived in the mesozoic era, specifically the triassic period, which was roughly around 230 million years ago.

4.) the first early human relatives were found roughly around d the neogene period, about 25 million years ago, and is in the cenozoic era.

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A gas mixture with a total pressure of 745 mmHg contains each of the following gases at the indicated partial pressures: CO2, 24

Setler79 [48]

Answer:

For Part A: The partial pressure of Helium is 218 mmHg.

For Part B: The mass of helium gas is 0.504 g.

Explanation:

For Part A:

We are given:

$p_{CO_2}=245mmHg\\p_Ar}=119mmHg\\p_{O_2}=163mmHg\\P=745mmHg$

To calculate the partial pressure of helium, we use the formula:

$P=p_{CO_2}+p_{Ar}+p_{O_2}+p_{He}$

Putting values in above equation, we get:

$745=245+119+163+p_{He}\\p_{He}=218mmHg$

Hence, the partial pressure of Helium is 218 mmHg.

For Part B:

To calculate the mass of helium gas, we use the equation given by ideal gas:

PV = nRT

or,

$PV=\frac{m}{M}RT$

where,

P = Pressure of helium gas = 218 mmHg

V = Volume of the helium gas = 10.2 L

m = Mass of helium gas = ? g

M = Molar mass of helium gas = 4 g/mol

R = Gas constant = $62.3637\text{ L.mmHg }mol^{-1}K^{-1}$

T = Temperature of helium gas = 283 K

Putting values in above equation, we get:

$218mmHg\times 10.2L=\frac{m}{4g/mol}\times 62.3637\text{ L.mmHg }mol^{-1}K^{-1}\times 283K\\\\m=0.504g$

Hence, the mass of helium gas is 0.504 g.

6 0

3 years ago

Which of these is an indication that a chemical reaction has occurred?

nevsk [136]

Formation Of A Gas.

3 0

4 years ago

Predict the electronegativity of the yet undiscovered element with Z = 119.

Lera25 [3.4K]

We know that the element Z = 119 would be placed right below the Fr, in the column of the alcaline metals.

We also know that the trend in the electronegativity is to decrease when you go up-down ia group.

The known electronegativities of the elements of this group are:

Li: 0.98
Na: 0.93
K: 0.82
Rb: 0.82
Cs: 0.79
Fr: 0.70

Then the hypotetical element Z = 119 would probably have an electronegativity slightly below 0.70, for sure in the range 0.60 - 0.70.

4 0

4 years ago

A sample of nitrogen monoxide occupies a volume of 400 mL at 100 °C and 720 mmHg.

konstantin123 [22]

The volume of nitrogen monoxide that occupy at STP is= 277 Ml

calculation
The volume is obtained using the combined gas law that is P1V1/T1= P2V2?
Where P1 = 720 MmHg
V1 = 400ml
T1= 100 +273= 373 K
At STP temperature = 273 K and pressure= 760 mm hg
therefore T2= 273 k
p2 = 760 mmhg
V2=?
make V2 the subject of the formula

V2= (T2 ×P1 ×V1)/(P2×T1)

V2 is therefore = (273k x720 mmhg x 400 ml)/(760 mmhg x373K) = 277 Ml

6 0

3 years ago

what is the balanced equation of magnesium carbonate decomposes on heating to form magnesium oxide and carbon dioxide

fenix001 [56]

Answer:

ExplaAt high temperatures MgCO3 decomposes to magnesium oxide and carbon dioxide. This process is important in the production of magnesium oxide. This process is called calcining: MgCO3 → MgO + CO2 (ΔH = +118 kJ/mol)

nation:

6 0

3 years ago