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3 years ago

6

A student wants to heat a piece of iron so that its temperature rises by 20 degrees C. What information does she need about the

iron to plan the experiment? A.)Temperature.
B.) Mass. C.) Conductivity. D.) Surface area.

2 answers:

LekaFEV [45]3 years ago

5 0

Mass................

grandymaker [24]3 years ago

4 0

The answer would be B: Mass. :-)

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1. What is the frequency of light with a wavelength of 1064 nm?

leonid [27]

Answer:

1) 2.8×10^14 Hz

2) 2.88×10^21 photons

Explanation:

Recall that the formula for the speed of a wave is v=λf, since we are talking about light, we can replace v with c hence; c=λf. Where;

c= speed of light = 3 ×10^8 m/s

λ= wavelength of light= 1064nm= 1064×10^-9 m

f= frequency of light= the unknown

Hence;

f= c/λ= 3×10^8/1064×10^-9

f= 2.8×10^14 Hz

Energy of a single photon=hf= 6.626×10^-34 Js × 2.8×10^14 s^-1 = 18.55×10^-20J

If 1 photon contains 18.55×10^-20J of energy

x photons contains 535 J of energy

x= 535/18.55×10^-20J

x= 2.88×10^21 photons

3 0

3 years ago

How many grams of KNO3 must be dissolved to<br> create 7.25L a 0.200M solution?

timofeeve [1]

Answer:

146.6 g

Explanation:

First we<u> calculate how many KNO₃ moles are there in 7.25 L of a 0.200 M solution</u>, using the <em>definition of molarity</em>:

Molarity = moles / liters

Molarity * liters = moles

0.200 M * 7.25 L = 1.45 moles

Then we<u> convert 1.45 moles of KNO₃ into grams</u>, using its <em>molar mass</em>:

1.45 mol * 101.103 g/mol = 146.6 g

7 0

3 years ago

How was the noble gas argon discovered

Mashcka [7]

Argon was discovered by Lord Rayleigh and Sir William Ramsay in 1894. It was isolated by examination of the residue obtained by removing nitrogen, oxygen, carbon dioxide, and water from clean air.

4 0

3 years ago

Read 2 more answers

A sample of 508.4 grams of copper completely reacted with oxygen to form 572.4 grams of a copper oxide product. how many grams o

Svet_ta [14]

According to law of conservation of mass, mass can neither be destroyed nor created in a chemical reaction. Thus, sum of masses of reactants must be equal to sum of masses of products in a reaction.

The chemical reaction is as follows:

$2Cu+O_{2}\rightarrow 2CuO$

Here, sum of masses of Cu and oxygen gas should be equal to CuO formed.

$2m_{Cu}+m_{O_{2}}=2m_{CuO}$

Thus, mass of oxygen will be:

$m_{O_{2}}=2(572.4-508.4)g=128 g$

This can be further proved as follows:

The balanced chemical reaction is as follows:

$2Cu+O_{2}\rightarrow 2CuO$

Here, 2 moles of Cu completely reacts with 1 mole of $O_{2}$ to give 2 moles of $CuO$ .

Thus, 1 mole of Cu reacts with 0.5 moles of $O_{2}$ .

The mass of Cu is 508.4 and molar mass is 63.546 g/mol, number of moles can be calculated as follows:

$n=\frac{m}{M}=\frac{508.4 g}{63.546 g/mol}=8 mol$

Thus, number of moles of $O_{2}$ reacting will be:

$n_{O_{2}}=8\times 0.5 mol=4 mol$

Molar mass of oxygen molecule is 32 g/mol thus, mass can be calculated as follows:

m=n×M=4 mol×32 g/mol=128 g/mol

This satisfies the law of conservation of mass.

7 0

3 years ago

Which of the following would be expected to be good solvents for cyclopentane. Choose all that apply. toluene, CgH5CH3 cyclohexa

Alik [6]

Answer:

cyclohexane

Explanation:

Solubility is determined by the principle , "like dissolves like" .

i.e. , if a compound is polar then it will dissolve in a polar compound only , and

if a compound is non - polar then it will dissolve in a non - polar compound only .

Hence , from the question ,

a good solvent for cyclopentane would be cyclohexane ,

since , both the compounds are non polar in nature , hence get solubilized ,

the other options mentioned are polar .

8 0

3 years ago