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3 years ago

What elements are formed by stars having a mass greater than eight suns?

1 answer:

6 0

Elements like helium and Boron are formed by stars having a mass of one to eight suns. When the mass of the stars are less than 5 times the mass of the sun,the star normally turns into a white dwarf

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Help asap plz its a test

Alex_Xolod [135]

Answer:

Explanation:

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3 years ago

Hoochie [10]

Answer:Active immunity involves both cell mediated and humoral immunity. Passive immunity is due to the presence of ready-made antibodies. Active immunity is durable. Active immunity offers effective protection against microbes

Explanation:

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4 years ago

If the rate of decrease for the partial pressure of N2H4N2H4 in a closed reaction vessel is 70 torr/htorr/h , what is the rate o

german

Answer:

$r_{NH_3}=140torr/h$

Explanation:

Hello,

In this case, the undergoing chemical reaction is:

$N_2H_4 (g) + H_2 (g) \rightarrow 2 NH_3$

Thus, in terms of pressures, the rate becomes:

$-r_{N_2H_4}=\frac{1}{2} r_{NH_3}$

Thus, the rate of change for the partial pressure of ammonia turns out:

$r_{NH_3}=2*(-r_{N_2H_4})\\r_{NH_3}=2*[-(-70torr/h)]\\r_{NH_3}=140torr/h$

The rate of decrease of partial pressure of urea is taken negative as it is a reactant whereas ammonia a product which has 2 as its stoichiometric coefficient.

Best regards.

7 0

3 years ago

Calculate the molecular weight of a dibasic acid.0.56gm of which is required 250ml of N/20 sodium hydroxide solution for neutral

Alekssandra [29.7K]

<u>Answer: </u>The molecular weight of the dibasic acid is 89.6 g/mol

<u>Explanation:</u>

Normality is defined as the amount of solute expressed in the number of gram equivalents present per liter of solution. The units of normality are eq/L. The formula used to calculate normality:

$\text{Normality}=\frac{\text{Given mass of solute}\times 1000}{\text{Equivalent mass of solute}\times \text{Volume of solution (mL)}}$ ....(1)

We are given:

Normality of solution = $\frac{1}{20}=0.05N$

Given mass of solute = 0.56 g

Volume of solution = 250 mL

Putting values in equation 1, we get:

$0.05=\frac{0.56\times 1000}{\text{Equivalent mass of solute}\times 250}\\\\\text{Equivalent mass of solute}=\frac{0.56\times 1000}{0.05\times 250}=44.8g/eq$

Equivalent weight of an acid is calculated by using the equation:

$\text{Equivalent weight}=\frac{\text{Molar mass}}{\text{Basicity}}$ .....(2)

Equivalent weight of acid = 44.8 g/eq

Basicity of an acid = 2 eq/mol

Putting values in equation 2, we get:

$44.8g/eq=\frac{\text{Molar mass}}{2eq/mol}\\\\\text{Molar mass}=(44.8g/eq\times 2eq/mol)=89.6g/mol$

Hence, the molecular weight of the dibasic acid is 89.6 g/mol

7 0

3 years ago

How much energy is required to melt a 500. gram block of iron? The heat of vaporization is 6090 J/g and the heat of fusion is 24

ki77a [65]

Answer:

Heat required = 1.23×10⁵J

Explanation:

Given:

Mass (m) = 500 gram

Specific heat = 6,090 J/g

heat of fusion = 247 J/g.

Find:

Heat required

Computation:

Heat required = 247 J/g× 500 g

Heat required = 1.23×10⁵J

4 0

4 years ago