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3 years ago

Which one of these is NOT a sign of chemical change? *

Chemistry

1 answer:

Gekata [30.6K]3 years ago

3 0

I think it’s light
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Rn-222 has a half-life of 3.82 days. If 25.0 g of Radon-22 was originally present, approximately how many grams would be left af

horsena [70]

Answer:

Approximately 0.39 g or 0.4 g if you're rounding up

Explanation:

15/3.82 = 3.92

Let's round that up to 4

That means 15 days is around 4 half lives

4 half lives means 1/16 of the original mass will be left

25/16 = 0.390625

6 0

3 years ago

A substance that can be broken down and recycled by bacteria and other decomposes is said to be__________

Stells [14]

Answer:The substance is Biodegradable

Explanation:

When something is biodegradable it can be broken down by organical processes or decomposers.

6 0

3 years ago

Identify the number of moles in 369 grams of calcium hydroxide. Use the periodic table and the polyatomic ion resource.

topjm [15]

Answer : The number of moles in 369 grams of calcium hydroxide is, 4.98 moles

Explanation : Given,

Mass of calcium hydroxide = 369 g

Molar mass of calcium hydroxide = 74.093 g/mole

Formula used :

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

Now put all the given values in this formula, we get the moles of calcium hydroxide.

$\text{Moles of calcium hydroxide}=\frac{369g}{74.093g/mole}=4.98mole$

Therefore, the number of moles in 369 grams of calcium hydroxide is, 4.98 moles

7 0

3 years ago

Which of the following tools is not used for measurement?

Verdich [7]

Answer:

tape measure

Explanation:

I am helping

8 0

2 years ago

Phosphorous trichloride and phosphorous pentachloride equilibrate in the presence of molecular chlorine according to the reactio

umka21 [38]

Answer : The value of $K_p$ at this temperature is 66.7

Explanation : Given,

Pressure of $PCl_3$ at equilibrium = 0.348 atm

Pressure of $Cl_2$ at equilibrium = 0.441 atm

Pressure of $PCl_5$ at equilibrium = 10.24 atm

The balanced equilibrium reaction is,

$PCl_3(g)+Cl_2(g)\rightleftharpoons PCl_5(g)$

The expression of equilibrium constant $K_p$ for the reaction will be:

$K_p=\frac{(p_{PCl_5})}{(p_{PCl_3})(p_{Cl_2})}$

Now put all the values in this expression, we get :

$K_p=\frac{(10.24)}{(0.348)(0.441)}$

$K_p=66.7$

Therefore, the value of $K_p$ at this temperature is 66.7

4 0

2 years ago