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4 years ago

Which of the following observations would indicate that a material is a pure substance?

Chemistry

2 answers:

Leokris [45]4 years ago

7 0

The correct answer is that a pure substance cannot be physically broken down into different types of atoms.

dem82 [27]4 years ago

7 0

It can’t be broken down into different types of atoms or can’t be broken down Into different types of molecules

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Which of the following forms a new substance? melting, evaporating, freezing or burning

Slav-nsk [51]

It would be burning be cause when you freeze, evaporate, or melt anything it is just changing how fast the atoms are moving . Think of it like water, ice, and steam, they are all the same thing but in different forms because of melting, evaporating,and melting. Burning is breaking it down.

4 0

4 years ago

Read 2 more answers

Charcoal from the dwelling level of the Lascaux Cave in France gives an average count of 0.97 disintegrations of ^14 C per minut

Verdich [7]

Answer:

Explanation:

count given by old sample = .97 disintegrations per minute per gram

count given by fresh sample = 6.68 disintegrations per minute per gram

Half life of radioactive carbon = 5568 years

rate of disintegration

dN / dt = λ N

In other words rate of disintegration is proportional to no of radioactive atoms present . As number reduces rate also reduces .

Let initial no of radioactive be N₀ and after time t , number reduces to N

N₀ / N = 6.68 / .97

Now

$N=N_0e^{-\lambda t}$

$\frac{N}{N_0} =e^{-\lambda t}$

$\frac{6.68}{.97} = e^{\lambda t}$

λ is disintegration constant

λ = .693 / half life

= .693 / 5568

= .00012446 year⁻¹

Putting the values in the equation above

$\frac{6.68}{.97} = e^{.00012446\times t}$

$6.8866 = e^{.00012446\times t}$

1.929577 = .00012446 t

t = 15503.6 years .

4 0

3 years ago

What is the ratio (in the form of a decimal) of the root-mean-square speed of 238UF6 to that of 235UF6 at constant temperature?

NNADVOKAT [17]

Answer:

ratio=0.996m/s

Explanation:

$RMS=\sqrt{\frac{3RT}{M} }$ ; M= molecular weight of compound;

RMS speed is inversly proportional to the molecular weight hence compound having less molecular weight will have more rms speed value.

$V1 for 238 UF_{6}; M1=238+114=352g/mole$

$V1 for 235 UF_{6}; M1=238+114=352g/mole$

$V1=\sqrt{\frac{3RT}{352} }$ ;

$V2=\sqrt{\frac{3RT}{349} }$ ;

$\frac{V1}{V2}$ =ratio of $238UF_{6} F6 to 235UF_{6}$ = $\sqrt{\frac{349}{352} }$ ;

$\frac{V1}{V2} =0.9957m/s;$

$\frac{V1}{V2} =0.996m/s;$

4 0

3 years ago

How many moles of Ag can be produced if 350. g of Cu are reacted with excess AgNO3 according to the equation Cu(s) + 2AgNO3(aq)

Ksju [112]

Hello.

balance the equation first
Cu + 2AgNO3 ----> [2Ag] + Cu(NO3)2


Now set up the equation 
350gCu*(1molCu/ 63.546g Cu) * (2molAg/1molCu) * (107.8682g Ag/1molAg)


Cancel out 1molCu with 1molCu, and cancel out 2molAg with 1molAg (it still remains 2mol Ag) 

You are left with 
350gCu*(1/63.546g Cu)*(2Ag/1)* (107.8682g Ag/1)


350gCu*1*2*107.8682= 75507.74g


now divide 75507.74g by 63.546g

you get [1188.2374972460896g Ag]

Have a nice day

3 0

3 years ago

Read 2 more answers

Giving brainly if correct and explained

kupik [55]

Answer:

Explanation:

A concentrated solution is one that has a lot of solute (the substance being dissolved) in the solvent (the substance doing the dissolving). When a solution is concentrated, it means it has a high ratio of solute to solvent, so the answer is D.

Hope this helps.

3 0

2 years ago