The half-life of iodine-131 is 8 days. How many milligrams of iodine-131
remain after 24 days if the original amount was 4.00 mg?
A. 1.33 mg
B. 0.667 mg
C. 0.500 mg
D. 0.444 mg

Answer:

13.7 liters

Explanation:

I took the test and got it right

The total volume of the NaCl solution whose molarity is 0.04 M is 13.7 liters.

Molarity of any solution is define as the number of moles of solute present in per liter of the solution and it will be represented as:

M = n/V

Mass from moles will be calculated as:
n = W/M, where

W = given mass of NaCl = 32g

M = molar mass of NaCl = 58.44g/mol

mole = 32g / 58.44g/mol = 0.547 mol

Molarity of solution = 0.04 M

On putting values on the above equation, we get volume as:
V = 0.547 mol / 0.04mol/L

V = 13.67 L = 13.7L

Hence required value of volume is 13.7 L.

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Answer:

O Al + Mg(NO3)2 -->

Explanation:

Answer:

Look down below

Explanation:

Environmmetal impacts that coal can cause is Sulfur dioxide (SO2), which contributes to acid rain and respiratory illness.

AND.....

Nitrogen oxides (NOx), which contribute to smog and respiratory illnesses. Particulates, which contribute to smog, haze, and respiratory illnesses and lung disease

Answer:

[tex]\boxed {\boxed {\sf 1290 \ g \ PI_3}}[/tex]

Explanation:

We want to convert from moles to grams, so we must use the molar mass.

The molar mass is the mass of 1 mole of a substance. It is the same as the atomic masses on the Periodic Table, but the units are grams per mole (g/mol) instead of atomic mass units (amu).

We are given the compound PI₃ or phosphorus triiodide. Look up the molar masses of the individual elements.

Note that there is a subscript of 3 after the I in the formula. This means there are 3 moles of iodine in 1 mole of the compound PI₃. We should multiply iodine's molar mass by 3, then add phosphorus's molar mass.

Use the molar mass as a ratio.

[tex]\frac {411.687262 \ g \ PI_3}{ 1 \ mol \ PI_3}[/tex]

We want to convert 3.14 moles to grams, so we multiply by that value.

[tex]3.14 \ mol \ PI_3 *\frac {411.687262 \ g \ PI_3}{ 1 \ mol \ PI_3}[/tex]

The units of moles of PI₃ cancel.

[tex]3.14 *\frac {411.687262 \ g \ PI_3}{ 1 }[/tex]

[tex]1292.698 \ g\ PI_3[/tex]

The original measurement of moles has 3 significant figures, so our answer must have the same. For the number we calculated, that is the tens place.

The 2 in the ones place tells us to leave the 9.

[tex]1290 \ g \ PI_3[/tex]

3.14 moles of phosphorous triiodide is approximately equal to 1290 grams of phosphorus triodide.

Answer:

[tex]V_2=10mL[/tex]

Explanation:

Hello there!

In this case, according to the given information, it will be possible for us to solve this problem by using the Boyle's law as an inversely proportional relationship between pressure and volume:

[tex]P_2V_2=P_1V_1[/tex]

In such a way, we solve for the final volume, V2, and plug in the initial volume and pressure and final pressure to obtain:

[tex]V_2=\frac{P_1V_1}{P_2} \\\\V_2=\frac{2.0atm*200.mL}{40.atm}\\\\V_2=10mL[/tex]

Regards!

Answer:

Phenolphthalein is a chemical compound with the formula C20H14O4 and is often written as "HIn" or "phph" in shorthand notation. Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions.

Answer:

Phenolphthalein is a chemical compound, a colorless crystalline solid, though pink in a alkaline solution, and is also used as an acid-base indicator.

Explanation:

Answer:

18x3=54 gram

Explanation:

When you express molecular mass (in case of molecule)/atomic mass(in case of atom) in gram it will be equivalent to one mole. For example:

12 gram Carbon atom = 1 mole of Carbon atom = N number of Carbon atom

16 gram Oxygen atom= 1 mole of Oxygen atom = N number of Oxygen atom

32 gram Oxygen molecule (O2) = 1 mole of Oxygen molecule (O2) = N number of Oxygen molecule (O2)

similarly 1 mole of water is equivalent to molecular mass of water x 3 that is 18x3=54 gram. It would constitute 3N molecules of water.

N: Avogadro's number : 6.022140857 × 10^23

Explanation:

The reaction rate decreases with a decrease in temperature. Catalysts can lower the activation energy and increase the reaction rate without being consumed in the reaction. Differences in the inherent structures of reactants can lead to differences in reaction rates.

Answer:

[tex]1oz=29.589ml[/tex]

Explanation:

From the question we are told that:

Initial Volume [tex]v_1=250ml[/tex]

Final Volume [tex]v_2=8.45oz[/tex]

Generally the equation for one ounce is mathematically given by

 [tex]1oz=\frac{v_1}{v_2}[/tex]

Therefore

 [tex]1oz=\frac{250}{8.45}[/tex]

 [tex]1oz=29.589ml[/tex]

Answer:

Cr is oxidised

and

Zn is reduced

[ Reduced reactant ] :

Cr^( + 3 ) + 3 e^( - 1 ) ===》 Cr^( 0 )

_____________________________

[ Oxidicided reactant ] :

Zn^(0) ===》Zn^( + 2 ) + 2 e^( - 1 )

Answer:

B - To increase the rate of the reaction

Explanation:

Catalysts speed up the reaction without being reactants or products, so aren't used up in the reaction.

Answer:

The correct answer is -

3. Butyne

4. Pentene

Explanation:

The names of such organic compounds are classified on the number of the carbon atoms and based on a number these prefixes are attached -

Meth - one carbon

Eth - two carbons

Prop - three carbons

But - four carbons

Pent - five carbons, and so on

The bonds can be identified by names of an organic compound by their suffixes -

- ane = single bond

- ene = double bond

-yne = triple bond

Thus, for question 3, carbon numbers are 4 and triple bond so Butyne, and similarly for question 4, 5 carbon atoms and double bond so Pentene.

Answer:

Moles of sodium = 15.0⋅g22.99⋅g⋅mol−1 = 0.652⋅mol . Given the stoichiometry of the reaction, clearly 0.652⋅mol sodium hydroxide will result.

Explanation:

please mark me

From the balanced chemical equation of the reaction, it is clear that, 2 moles or 46 g of sodium metal produce 2 moles of NaOH. Then, 15 g or 0.65 moles of Na metal will give 0.65 moles or 26 g of NaOH.

The balanced chemical equation of a reaction represent the correct stoichiometry of all the reactants and products in the reaction. It is balanced as per the law of conservation of masses. Hence, the total mass of the reactant side is equal to the total mass of the product side.

From the given balanced chemical equation of the reaction, it is clear that, 2 moles of Na reacts with one mole of water to give two moles of NaOH and one mole of hydrogen gas.

Atomic mass of Na = 23 g/mol

no.of moles in 15 g = 15 g /23g/mol = 0.65 moles.

2 moles of Na gives 2 moles of NaOH. Then, 0.65 moles of Na will given 0.65 moles of NaOH.

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Answer:

D. The Sun

Explanation:

The Sun does not affect global wind belts.

Land breeze does not affect global wind belts whereas other factors such as air pressure, Coriolis effect and the sun affected global wind patterns.

Unequal heating of the Earth's surface forms large global wind patterns. Those area which are near the equator, the sun warm air and this warm air rises at the equator and moves toward the poles. At the poles, the cooler air sinks and moves back toward the equator.

So we can conclude that land breeze does not affect but sun creates affect on the global wind pattern.

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Answer: The new temperature is [tex]63^{o}C[/tex].

Explanation:

Given: [tex]V_{1}[/tex] = 1.90 L,    [tex]T_{1} = 21.0^{o}C[/tex]

[tex]V_{2}[/tex] = 5.70 L,         [tex]T_{2} = ?\\[/tex]

Formula used to calculate new temperature is as follows.

[tex]\frac{V_{1}}{T_{1}} = \frac{V_{2}}{T_{2}}[/tex]

Substitute the values into above formula as follows.

[tex]\frac{V_{1}}{T_{1}} = \frac{V_{2}}{T_{2}}\\\frac{1.90 L}{21.0^{o}C} = \frac{5.70 L}{T_{2}}\\T_{2} = 63^{o}C[/tex]

Thus, we can conclude that the new temperature is [tex]63^{o}C[/tex].

Answer:

The composition of a pure substance is always the same, regardless of the source, but the composition of a mixture can vary.

Mixtures can be separated into their components by physical changes; some pure substances can be separated into components by chemical change.

Explanation:

A chemically pure substance has a well defined and constant composition. The composition of a chemically pure substance remains the same irrespective of its source. Also, the components of a chemically pure substance may be separated by chemical changes.

Mixtures have a variable composition depending on their  respective sources. The composition of a mixture varies with the source of the mixture and mixtures are separated by physical processes.

Answer:

Explanation: a) Reaction is exothermic because heat is released

                       If temperature is lowered, amount of products is increased,

                      equilibrium transfers to right

b) If pressure decreases, equilibrium transfers to direction in which amount of gas moles is greater, also in left (reactants)

c) If Oxygen is removed, reaction which produces more oxygen is favoured, also balance changes to reactansts (left)

d) Adding product causes equilibrium transfer to left (reactansts)

Answer:

alpha  decay

Explanation:

If the half-life for carbon-14 is 5730 years, then it will take 11,460 years to complete die of this sample.

Half life period is a time of decay in which concentration of reactant is left half of its initial concentration, means half of the reactant will convert into product.

Total time of decay will be calculated as:

T = (t)ⁿ, where

t = half life time = 5730 years

n = number of half lives = 2 (given)

On putting values, we get

T = (5730)² = 11,460 years

Hence required time for decay is 11,460 years.

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Answer:

The first part is 5 and the second part is 28,650

Answer:

27*6 dkfkdh hshsnnsbssshs ss. hhshsns svs s ssjssgsyz

Explanation:

ysgshssbs

Answer:

Balanced equation:

CaCO3 (s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)

1mol CaCO3 will react with 2 mol HCl

Mol HCl in 32.8mL of 1.25M solution = 32.8mL / 1000mL/L * 1.25mol /L = 0.041 mol HCl

This will react with 0.041/2 = 0.0205 mol CaCO3

Molar mass CaCO3 = 100g/mol

Mass of CaCO3 reacted = 0.0205mol *100g/mol = 2.05g CaCO3.

Grams are the unit of weight or mass that depicts the quantity of a substance. The mass of calcium carbonate reacted is 2.05 gm.

Mass is the product of the moles of the compound and its molar mass, it is given in grams.

The balanced chemical reaction is given as:

[tex]\rm CaCO_{3} (s) + 2HCl(aq) \rightarrow CaCl_{2}(aq) + CO_{2}(g) + H_{2}O(l)[/tex]

From the reaction, 1 mole of calcium carbonate reacts with 2 moles of hydrochloric acid.

Moles of hydrochloric acid is calculated as:

[tex]\begin{aligned} \rm n &= \rm Molarity \times Volume (L)\\\\&= 0.0328 \times 1.25\\\\&= 0.041\;\rm mol\end{aligned}[/tex]

Now, the moles of calcium carbonate it will react with will be 0.0205 moles.

Mass of calcium carbonate is calculated as:

[tex]\begin{aligned} \rm mass &= \rm molar\; mass \times moles\\\\&= 0.0205 \times 100\\\\&= 2.05 \; \rm g\end{aligned}[/tex]

Therefore, 2.05 gm of calcium carbonate is needed to react with 15.2 gm of hydrochloric acid.

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Answer:

[tex]1 \: mole = 6.02 \times {10}^{23} \: atoms \\ 6.5 \: moles = (6.5 \times {6.02 \times 10}^{23} ) \: atoms \\ = 3.913 \times {10}^{24} \: atoms[/tex]

Explanation:

Answer ⬇️

These mills employed millstones that rotated against one another to crush grains into flour mill machine. They rely on a process of crushing grain between two rapidly rotating rollers, then separating the ground grain into individual components, including bran, germ and endosperm.

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Answer:

Explanation:

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