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Nostrana [21]
3 years ago
14

If you were asked to convert 25 cg to the unit hg, which of the following would be the first fraction used in the conversion? on

e hg over ten squared g ten squared cg over one hg ten squared hg over one cg ten to the negative second power g over one cg
Chemistry
1 answer:
zhannawk [14.2K]3 years ago
4 0
We are asked to convert 25 cg to units of hg.

1 cg = 1 centigram = 10⁻² g
1 hg = 1 hectogram = 10² g

The options given are:

a) 1 hg/ 10² g
b) 10² cg/ 1 hg
c) 10² hg/ 1 cg
d) 10⁻² g/ 1 cg

To convert 25 cg to 1 hg, we could convert the 25 cg to grams first, then grams to hg.

25 cg · 10⁻² g/ 1cg = 0.25 g

Here we have converted our number from cg to grams. We can use another conversion of grams to hg to complete the conversion.

0.25 g · 1 hg/ 10² g = 0.0025 hg

Therefore, the first conversion we used was d) 10⁻² g/ 1 cg.
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The amount of 217 mg of an isotope is given by A(t) = 217 € -0.0171, where t is time in years since the initial amount of 217 mg
Maru [420]

The amount left after 20 years = 154.15 mg

<h3>Further explanation </h3>

The atomic nucleus can experience decay into 2 particles or more due to the instability of its atomic nucleus.  

Usually radioactive elements have an unstable atomic nucleus.  

The main particles are emitted by radioactive elements so that they generally decay are alpha (α), beta (β) and gamma (γ) particles  

The decay formula for isotope :

\tt \large{\boxed{\bold{A(t)=217e^{-0.0171t}}}

Then for t=20 years, the amount left :

\tt A(t)=217e^{-0.0171\times 20}\\\\A(t)=154.15~mg

4 0
3 years ago
Read 2 more answers
Calcium nitrate tetrahydrate dissolves in cold water to the extent of 266 g per 100 cm3. What is the concentration of nitrate io
Soloha48 [4]

Answer : The correct option is, (b) 22.5 M

Explanation : Given,

Mass of calcium nitrate tetrahydrate = 266 g

Molar mass of calcium nitrate tetrahydrate  = 236.15 g/mole

Volume of solution = 100cm^3=100mL

Molarity : It is defined as the moles of solute present in one liter of solution.

Formula used :

Molarity=\frac{\text{Mass of calcium nitrate tetrahydrate }\times 1000}{\text{Molar mass of calcium nitrate tetrahydrate }\times \text{volume of solution in ml}}

Now put all the given values in this formula, we get:

Molarity=\frac{266g\times 1000}{236.15g/mole\times 100ml}=11.26mole/L=11.26M

As calcium nitrate tetrahydrate dissociate to give 1 mole of calcium ion, 2 moles of nitrate ion and 4 moles of water.

The concentration of nitrate ion = 2\times 11.26M=22.5M

Thus, the concentration of nitrate ion is, 22.5 M

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3 years ago
According to VSEPR Theory, the molecular geometry for CH3+ is
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I think it’s C but anybody can correct me if I’m wrong
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How many moles of sodium ions are present in 0.25 kg of a 2.0 m solution of sodium chloride in water
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3 years ago
calculate how much acid (acetic acid) and how much conjugate base (sodium acetate) must be used to make 500ml of a 0.8m acetate
kirza4 [7]

For the desired pH of 5.76, 0.365 mol of acetate and 0.035 mol of acid are to be added

let the concentration of acetate be x

then the concentration of acid will be (0.8 - x)

pKa of acetate buffer = 4.76

pH = pKa + log([acetate]/[acid])

⇒4.76 = 4.76 + log(x/(0.8-x))

⇒log(x/(0.8-x)) = 0

⇒x/(0.8-x) = 1

⇒x = 0.4

Therefore

[acetate] = x = 0.4

[acid] = 0.8-x =0.4 M

number of mol = concentration *(volume in mL)

number of mol of acetate = 0.4*0.5

= 0.20 mol

number of mol acid = 0.4*0.5

= 0.20 mol

when desired pH = 5.76

pH = pKa + log([acetate]/[acid])

⇒5.76 = 4.76 + log(x/(0.8-x))

⇒log(x/(0.8-x)) = 1

⇒x/(0.8-x) = 10

⇒x = 8 - 10x

⇒x = 8/11

⇒x= 0.73

[acetate] = x= 0.73

[acid] = 0.8-x = 0.07 M

number of mol = concentration * (volume in mL)

number of mol acetate to be added = 0.73*0.5 = 0.365 mol

number of mol acid to be added = 0.07*0.5 = 0.035 mol

Problem based on acetic acid required to maintain a certain pH

brainly.com/question/9240031

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1 year ago
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