Water boils at a temperature of _______ degrees on the celsius scale. a. 212 b. 194 c. 100 d. 90

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Galina-37 [17]

Answer:

c

Explanation:

defiantly

3 0

2 years ago

A sample of radioactive waste has a half-live of 40 years and an activity level of 4 curies. After how many years will the activ

Westkost [7]

After 160 years, the activity level of the sample will be 0.5 curies.

Half life of any radioactive waste is the half decay of that product.

The formula is $\dfrac{\lambda }{\lambda_1} = 2^\dfrac{a}{b}$

Where, λ is 4 cruies

λ1 is 0.5 cruies

b = 40 years

Putting the values in the equation

$\dfrac{4}{0.5} = 2^\dfrac{a}{40}\\\\\\\dfrac{a}{40} = 4\\ = 160 years$

Thus, the correct option is 160 years.

Learn more about half-life

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8 0

1 year ago

Why is carbon used to extract metals from their oxides?

pashok25 [27]

Answer:

If a metal is less reactive than carbon, it can be extracted from its oxide by heating with carbon. The carbon displaces the metal from the compound, and removes the oxygen from the oxide. This leaves the metal.

Explanation:

4 0

2 years ago

Instant cold packs, often used to ice athletic injuries on the field, contain ammonium nitrate and water separated by a thin pla

RSB [31]

<u>Answer:</u> The enthalpy change of the reaction is -27. kJ/mol

<u>Explanation:</u>

To calculate the mass of water, we use the equation:

$\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}$

Density of water = 1 g/mL

Volume of water = 25.0 mL

Putting values in above equation, we get:

$1g/mL=\frac{\text{Mass of water}}{25.0mL}\\\\\text{Mass of water}=(1g/mL\times 25.0mL)=25g$

To calculate the heat released by the reaction, we use the equation:

$q=mc\Delta T$

where,

q = heat released

m = Total mass = [1.25 + 25] = 26.25 g

c = heat capacity of water = 4.18 J/g°C

$\Delta T$ = change in temperature = $T_2-T_1=(21.9-25.8)^oC=-3.9^oC$

Putting values in above equation, we get:

$q=26.25g\tiimes 4.18J/g^oC\times (-3.9^oC)=-427.9J=-0.428kJ$

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of ammonium nitrate = 1.25 g

Molar mass of ammonium nitrate = 80 g/mol

Putting values in above equation, we get:

$\text{Moles of ammonium nitrate}=\frac{1.25g}{80g/mol}=0.0156mol$

To calculate the enthalpy change of the reaction, we use the equation:

$\Delta H_{rxn}=\frac{q}{n}$

where,

q = amount of heat released = -0.428 kJ

n = number of moles = 0.0156 moles

$\Delta H_{rxn}$ = enthalpy change of the reaction

Putting values in above equation, we get:

$\Delta H_{rxn}=\frac{-0.428kJ}{0.0156mol}=-27.44kJ/mol$

Hence, the enthalpy change of the reaction is -27. kJ/mol

4 0

3 years ago

Which function of lysosomes is carried out by vacuoles in plant cells

user100 [1]

Answer:

Lysosomes are predominantly found in eukaryotic animal cells and are responsible for breaking down cellular debris

Explanation:

7 0

3 years ago