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3 years ago

How much heat is required to raise the temperature of 45.5 g of water from its melting point to its boiling point?

1 answer:

3 0

First, melt the ice, H2O(s):

45.5gH2O x 333J/1gH2O = 15,152 J 

Next, raise the temperature of the water, H2O(l): 

45.5gH2O x 100degC x 4.184J/1gH2O-1degC = 19,037 J 

Finally, addem all up: 

34,200 J = 34.2 kJ to three significant figures

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How many grams of CO-60 result in 1 Millicuire of activity? How many years until the activity decays to 1 microcuire tl/2 =5.3 Y

vredina [299]

Answer:

m =8.81*10^{-6}grams

time t = 52.8 year

Explanation:

GIVEN DATA:

the half life of the CO-60 is, T_1/2 = 5.27 years = 1.663 e+8 s

activity dN/dt = 1 mCi = 3.7 X 10^7 decay/s

activity , $dN/dt = N* \lambda$

$\frac{dN}{dt} = N* \frac{ln2}{T_1/2}$

$N = \frac{(dN/dt )(T1/2)}{ln2}$

= ( 3.7 X 10^7 )(1.663*10^8 ) / ln2

= 8.877*10^{16}

Number of moles:

n = N/NA = 8.877*10^{16} / 6.022X10^23 = 1.474*10^{-7} mol

mass of the CO-60 is,

m = n*M = [1.474*10^{-7} mol]*[59.93 grams /mol] = 8.81*10^{-6}grams

-----------------------------------------------------------------------------------------

time t = -[T1/2 / ln2]*ln[N/N0]

= - [5.3 years / ln2]*ln[1x10-6/1x10-3]

= 52.8 year

8 0

4 years ago

A 60-m-long chain hangs vertically from a cylinder attached to a winch. Assume there is no friction in the system and that the

Mariulka [41]

Answer:

part (a). 176580 J

part (b). 197381 J

Explanation:

Given,

Density of the chain = $\rho\ =\ 10\ kg/m.$
Length of the chain = L = 60 m
Acceleration due to gravity = g = 9.81 $m/s^2$

part (a)

Let dy be the small element of the chain at a distance of 'y' from the ground.

mass of the small element of the chain = $\rho dy$

Work done due to the small element,

$dw\ =\ \rho g (60\ -\ y)dy\\$

Total work done to wind the entire chain = w

$w\ =\ \displaystyle\int_{0}^{L} \rho g(60\ -\ y)dy\\\Rightarrow w\ =\ \rho g\left |(60y\ -\ \dfrac{y^2}{2})\ \right |_{0}^{60}\\\Rightarrow w\ =\ 10\times 9.81\times (60\times 60\ -\ \dfrac{60^2}{2})\\\Rightarrow w\ =\ 176580\ J$

part (b)

mass of the block connected to the chain = m = 35 kg

Total work done to wind the chain = work done due to the chain + work done due to the mass

$\therefore W\ =\ w\ +\ mgL\\\Rightarrow W\ =\ 176580\ +\ 35\times 9.81\times 60\\\Rightarrow W\ =\ 176580\ +\ 20601\\\Rightarrow W\ =\ 197381\ J$

4 0

3 years ago

What is another unit for momentum besides kg-m/s? a. N b. N-s c. N-s2 d. N/s

lara [203]

'Newton-second' is dimensionally equivalent to 'kilogram-meter/second'.

8 0

3 years ago

These four surfaces are opaque; that is they reflect or absorb certain rays of light determine the color

masya89 [10]

In the first figure, the surface absorbs all colors except for green light, which is reflected: so, the surface will appear as green to our eyes, because green is the only color which is reflected by that surface.

Similarly, in the second figure, the surface absorbs all colors except for blue, and so the surface will appear blue to our eyes.

In the third figure, the surface absorbs all colors, so it will appear black to our eyes (because no colors are reflected, and black=absence of colors).

In the fourth figure, all colors are reflected: this means the surface will appear white to our eyes (white= sum of all colors).

4 0

4 years ago

Question one please! This is 8th grade science btw.

yKpoI14uk [10]

Good Luck, NYAYAYAYAYa

8 0

3 years ago