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3 years ago

Pls assist if you can.Reasons why hydrogen was chosen as a standard reference to other elements

Chemistry

1 answer:

MrMuchimi3 years ago

4 0

Answer:

See below

Step-by-step explanation:

Hydrogen either reacts with or is formed by reactions with many other elements, so chemists could use it directly to determine their relative masses.
Hydrogen has the smallest atomic mass, so it was convenient to give H a relative atomic mass of 1 and assign those of other elements as multiples of this number.

The O = 16 scale became the standard in 1903 and carbon-12 was chosen in 1961.

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The radioactive substance cesium-137 has a half-life of 30 years. The amount At (in grams) of a sample of cesium-137 remaining a

stealth61 [152]

<u>Answer:</u> The amount of sample left after 20 years is 288.522 g and after 50 years is 144.26 g

<u>Explanation:</u>

We are given a function that calculates the amount of sample remaining after 't' years, which is:

$A_t(t)=458\times (\frac{1}{2})^{\frac{t}{30}$

<u>For t = 20 years</u>

Putting values in above equation:

$A_t(t)=458\times (\frac{1}{2})^{\frac{20}{30}$

$A_t(t)=288.522g$

Hence, the amount of sample left after 20 years is 288.522 g

<u>For t = 50 years</u>

Putting values in above equation:

$A_t(t)=458\times (\frac{1}{2})^{\frac{50}{30}$

$A_t(t)=144.26g$

Hence, the amount of sample left after 50 years is 144.26 g

6 0

3 years ago

15 points + brainliest pls help :(

Komok [63]

Answer:

27 g

Explanation:

M(C6H12O6) = 6*12 + 12*1 + 6*16 = 180 g/mol

100 mL = 0.1 L solution

1.5 M = 1.5 mol/L

1.5 mol/L * 0.1 L = 0.15 mol C6H12O6

0.15 mol * 180 g/1 mol = 27 g C6H12O6

6 0

3 years ago

Which of the following lists the correct symbol for the ion that tin forms when it loses 2 electrons, the correct classification

ser-zykov [4K]

Answer:

$\huge\boxed{\sf Option \ A}$

Explanation:

The symbol for TIN is Sn.

When Sn loses 2 electrons, it gets a double positive charge ( +2 ) and becomes $\sf Sn ^{+2}$ .

It becomes a cation.

The name of Ion is Tin ( II ) Ion.

$\rule[225]{225}{2}$

Hope this helped!

6 0

3 years ago

Read 2 more answers

A qué llamamos fluido en reposo

Svetach [21]

Answer:

Lo llamas hidrostática

Explanation:

7 0

2 years ago

Read 2 more answers

You are requested to reduce the size of 50 ton/hr of a given solid. The size of the feed is such 80% passes a 4-in (76.2 mm) scr

defon

Answer:

1) The power needed to process 50 ton/hr is 135.4 HP.

2) The void fraction of the bed is 0.37.

Explanation:

1) For this type of milling operations, we can estimate the power needed for an operation according to the work index (Ei), the passing size of the circuit feed (F80) and the passing size of the product (P80).

We assume the units of Ei are kWh/t.

The equation that relates this parameters and the power is (size of particles in μm):

$W=Ei*(\frac{10}{\sqrt{P80}} -\frac{10}{\sqrt{F80}} )\\\\W=9.45*(\frac{10}{\sqrt{3175\mu m}} -\frac{10}{\sqrt{76200mm}} )\\\\\\W=9.45*(0.1774+0.0362)=2.019 kWh/t$

The power needed to process 50 ton/hor is

$P=2.0194\frac{kWh}{Ton}*\frac{50Ton}{h}*\frac{1.341HP}{1kW}= 135.4 \, HP$

2) The density of the packed bed can be expressed as

$\rho=f_v*\rho_v+f_s*\rho_s$

being f the fraction and ρ the density of every fraction. We know that the density of the void is 0 (ρv=0) and that fv=1-fs (the sum of the fractions ois equal to the total space).

Then we can rearrange

$\rho=f_v*\rho_v+f_s*\rho_s\\\\\rho=f_v*0+(1-f_v)*\rho_s\\\\\rho/\rho_s=1-f_v\\\\f_v=1-\rho/\rho_s=1-990/1570=1-0.63=0.37$

The void fraction of the bed is 0.37.

6 0

3 years ago