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2 years ago

Define what is halflife

1 answer:

8 0

Half-life is the time it takes for a substance to lose half of its pharmacological, physiological, or radiological activity.

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100 points

Mariana [72]

Answer:

Where is the puzzle!??

I surely can help you

5 0

2 years ago

Read 2 more answers

Hypothesis and Data Collection Part A The image shows three different liquids: water, water with salt, and vinegar. The pH of ea

Norma-Jean [14]

Answer:

The water would be neutral, (usually 7). The salt water would be the same (7) and the vinegar would be very acidic. (probably 2).

Explanation:

7 0

1 year ago

A sample of CaCO3 (molar mass 100. g) was reported as being 30. percent Ca. Assuming no calcium was present in any impurities, c

natka813 [3]

Answer:

Approximately 75%.

Explanation:

Look up the relative atomic mass of Ca on a modern periodic table:

Ca: 40.078.

There are one mole of Ca atoms in each mole of CaCO₃ formula unit.

The mass of one mole of CaCO₃ is the same as the molar mass of this compound: $\rm 100\; g$ .
The mass of one mole of Ca atoms is (numerically) the same as the relative atomic mass of this element: $\rm 40.078\; g$ .

Calculate the mass ratio of Ca in a pure sample of CaCO₃:

$\displaystyle \frac{m(\mathrm{Ca})}{m\left(\mathrm{CaCO_3}\right)} = \frac{40.078}{100} \approx \frac{2}{5}$ .

Let the mass of the sample be 100 g. This sample of CaCO₃ contains 30% Ca by mass. In that 100 grams of this sample, there would be $\rm 30 \% \times 100\; g = 30\; g$ of Ca atoms. Assuming that the impurity does not contain any Ca. In other words, all these Ca atoms belong to CaCO₃. Apply the ratio $\displaystyle \frac{m(\mathrm{Ca})}{m\left(\mathrm{CaCO_3}\right)} \approx \frac{2}{5}$ :

$\begin{aligned} m\left(\mathrm{CaCO_3}\right) &= m(\mathrm{Ca})\left/\frac{m(\mathrm{Ca})}{m\left(\mathrm{CaCO_3}\right)}\right. \cr &\approx 30\; \rm g \left/ \frac{2}{5}\right. \cr &= 75\; \rm g \end{aligned}$ .

In other words, by these assumptions, 100 grams of this sample would contain 75 grams of CaCO₃. The percentage mass of CaCO₃ in this sample would thus be equal to:

$\displaystyle 100\%\times \frac{m\left(\mathrm{CaCO_3}\right)}{m(\text{sample})} = \frac{75}{100} = 75\%$ .

3 0

2 years ago

Cell-mediated immunity differs from humoral immunity in that _____.

inessss [21]

As far as I remember, cell-mediated immunity differs from humoral immunity in that they respond differently to invaders

8 0

2 years ago

Any body help me? please Q 17

iVinArrow [24]

Question 17

The subscript 2 is the atomic number for helium and subscript 4 is the mass number for Helium

explanation

when writing down an isotope of an element the mass number of that isotope is written in upper side of the chemical symbol, while atomic number is written on the lower side.

Since 4 is on upper side it is the mass number of He, while 2 is the atomic number since it is on lower side.

Question 18

The type of radiation emitted when polonium -212 form lead 208 is an alpha particle

explanation

Alpha decay is a decay in which an atomic nuclei emit an alpha particles and be transformed into different atomic nuclei with a mass number that is reduced by 4

polonium 212 is reduced by 4 to form lead 208 therefore it undergo alpha particle decay.

8 0

2 years ago

Define what is halflife​

Define what is halflife