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3 years ago

11

What was discovered first helium or samarium?

1 answer:

lana [24]3 years ago

7 0

The correct answer is helium, but both discoveries were quite close. Helium was discovered in 1868 during a solar eclipse by French astronomer Jules Janssen, while samarium was discovered in 1879 by a French chemist Paul Émile Lecoq de Boisbaudran.

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Jake hangs two balloons from a desk so that they are close together but not touching. Jake rubs one balloon with a wool cloth. H

kari74 [83]

The objects that are rubbed together will create charges among themselves due to friction.
(1) The balloon rubbed with a wool cloth will be charged.
(2) If she comb near a small, uncharged object nothing will change.
(3) This is a scientific investigation because it does not involved a step by step process to answer a scientific query.

3 0

3 years ago

Read 2 more answers

What expression approximates the volume of O2 consumed, measure at STP, when 55 g of Al reacts completely with excess O2?2 Al(s)

nikdorinn [45]

Answer : The volume of $O_2$ consumed are, $0.75\times 2\times 22.4$ L.

Explanation :

The balanced chemical reaction will be:

$4Al(s)+3O_2(g)\rightarrow 2Al_2O_3(s)$

First we have to calculate the moles of Al.

$\text{Moles of }Al=\frac{\text{Mass of }Al}{\text{Molar mass of }Al}$

Molar mass of Al = 27 g/mole

$\text{Moles of }Al=\frac{55g}{27g/mol}=2mole$

Now we have to calculate the moles of $O_2$ .

From the reaction we conclude that,

As, 4 mole of Al react with 3 moles of $O_2$

So, 2 mole of Al react with $\frac{3}{4}\times 2=0.75\times 2$ moles of $O_2$

Now we have to calculate the volume of $O_2$ consumed.

As we know that, 1 mole of substance occupies 22.4 liter volume of gas.

As, 1 mole of $O_2$ occupies 22.4 liter volume of $O_2$ gas

So, $0.75\times 2$ mole of $O_2$ occupies $0.75\times 2\times 22.4$ liter volume of $O_2$ gas

Therefore, the volume of $O_2$ consumed are, $0.75\times 2\times 22.4$ L.

3 0

3 years ago

The volume of a gas is doubled while the temperature is held constant. How does the gas pressure change

Inessa05 [86]

As the volume of the container increases, the gas pressure decreases. They are directly proportional. This is supported by Boyle's Law.

8 0

3 years ago

Read 2 more answers

14. A child's lungs can hold 2.20 L. How many grams of air do her lungs hold at a pressure of

Alenkasestr [34]

Answer:

Explanation:

Use the gas equation: PV=nRT

P=pressure

V=Volume

R= gas constant of around 8.31 J/K/mol

T=temperature

n= number of moles

To find n, Rearrange:

n=PV/RT

102kPa= 102,000 kilo pascals which standard form is 102 x 10^3

Convert Celsius to kelvin, which you just add 273.15. So:

37+273.15=310.15 K round to a whole number is 310 K

Sub in all numbers to calculate the mol

n= 102 x 10^3 x 2.20 x 10^3/ 8.31 x 310 (cross out 10^3 as this will make a big number)

n=102 x 2.2/8.31 x 310 =0.087 mol

We know 1 g=29 moles

Multiply 29 moles with 0.087 to find the grams

29*0.087=2.523, which to one d.p is 2.5 g

Hence, the child's lung will hold 2.5 g of air.

Hope this helps you :)

Have a nice day!!

5 0

4 years ago

Read 2 more answers

A jet is goes from 180km/s to 139km/s in 22 seconds. What is it's acceleration?

jeyben [28]

180 km/s V= 25

explanation: i had the same assignment

5 0

3 years ago