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Allushta [10]
3 years ago
7

What is cement and who invented it?

Chemistry
1 answer:
Sonja [21]3 years ago
5 0

Answer:

Cement is a combination of calcium, silicone, aluminum, iron and lots of other ingredients to make side walks, home made crafts, etc. The person who invented concrete is Joseph Aspdin.

Explanation:

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Magnesium and iron are metallic elements. How does a mole of magnesium compare with a mole of iron?
Dennis_Churaev [7]
<span>They both have the same number of atoms. The molar mass of CO2 is 44.01 g/mol.</span>
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3 years ago
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The current global population is 7.7 billion people, and the WHO estimates the minimum water need per person per day is 15 L. An
anygoal [31]

Answer:

a) The amount of freshwater available as groundwater, lakes and rivers, does not even reach one day the need for consumption for the current global population.  ( t = 5.489 E-13 day )

b) The annual terrestrial precipitation, reaches to sustain the drinking water needs for the current global population

Explanation:

Let P = 7.7 billion people = 7.7 E12 person

∴ water needed for the total population for one day:

⇒ water amount  = 7.7 E12 person * ( 15 L / person. day ) = 1.155 E14 L H2O /day

⇒ water amount = 1.155 E14 L H2O/day * 1 E1 Km² H2O / L H2O = 1.155 E15 Km² H2O/day * ( 365 day / year ) = 4.216 E17 Km²/year

∴ freshwater available:

freshwater = 6.34 E2 Km² H2O

how long will this water sustain the current population?

⇒ t = 6.34 E2 Km² * day / 1.155 E15 Km² = 5.489 E-13 day

this amount of freshwater does not even meet the need of the current global population.

∴ the annual terrestrial precipitation (Py) = 505000 Km³/year..........from literature

⇒ Py = 505000 Km³ H2O/year * ( 1000 m/Km )³ * ( 1000L/m³ )

⇒ Py = 5.05 E17 L H2O/year * ( 1 E1 Km² / L ) = 5.05 E18 Km² H2O/year

⇒ Py > water amount

the annual terrestrial precipitation of water, reaches to sustain the drinking water needs.

4 0
3 years ago
What is the molality of a solution containing 10.0 G of NA2 S04 and 1000.0 G of water
galina1969 [7]

Explanation:

1 literThe total of water is equal to 1000.0 g of water

we need to find the molality of a solution containing 10.0 g of dissolved in  Na₂S0₄1000.0 g of water

1. For that find the molar mass

Na:  2 x 22.99= 45.98

S:  32.07

O:  4 x 16= 64

The total molar mass is 142.05

We have to find the number of moles, y

To find the number of moles divide 10.0g by 142.05 g/mol.

So the number of moles is 0.0704 moles.

For the molarity, you need the number of moles divided by the volume. So, 0.0704 mol/1 L.

The molarity would end up being 0.0704 M

The molality of a solution containing 10.0 g of Na2SO4 dissolved in 1000.0 g of water is  0.0704 Mliter

7 0
3 years ago
Determine the number of significant digits in each number and list the specific significant digits. 1. 306,000 2. 0.0073 3. 39.9
Lelechka [254]

Answer:

1. 306,000: three significant figures because the last three zeros are not preceded by a decimal point.

2. 0.0073: two significant figures because the the leftmost zeros are not significant.

3. 39.9999: six significant figures because all these numbers are nonzero digits.

4. 25.00: four significant figures because right-handed zeros, after a decimal point, are significant.

5. 40,000,021: eight significant figures because intermediate zeros are significant.

6. 45,250.0: six significant figures because al the zeros are to the right of the nonzero digits.

7. 0.00011: two significant figures as well as #2.

8. 420.030700: nine significant figures because all the zeros are to the right of the first nonzero digits and after the decimal point.

Explanation:

Hello there!

In this case, by considering the given numbers, we can proceed as follows, by keeping in mind the rules for assigning significant figures:

1. 306,000: three significant figures because the last three zeros are not preceded by a decimal point.

2. 0.0073: two significant figures because the the leftmost zeros are not significant.

3. 39.9999: six significant figures because all these numbers are nonzero digits.

4. 25.00: four significant figures because right-handed zeros, after a decimal point, are significant.

5. 40,000,021: eight significant figures because intermediate zeros are significant.

6. 45,250.0: six significant figures because al the zeros are to the right of the nonzero digits.

7. 0.00011: two significant figures as well as #2.

8. 420.030700: nine significant figures because all the zeros are to the right of the first nonzero digits and after the decimal point.

Regards!

7 0
3 years ago
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