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3 years ago

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(please help ;-; 30 points)This is a diagram developed by Ejnar Hertzprung and Henry Russell that shows how the magnitude, tempe

rature, color, and spectral class of a star are all related.
whats the term for this? (hint: the beginning letters are H and e)

1 answer:

Nat2105 [25]3 years ago

4 0

Answer: is it a Hertzprung- Russell diagram?

Explanation:

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If a reaction taking place in a flask shows a drop in temperature, which type of reaction is it? Options: exothermic reactions e

liubo4ka [24]

Answer:

exothermic reaction

Explanation:

If there is a drop in temperature, then energy was lost to the surroundings because temperature is the average measure of kinetic energy. An exothermic reaction would result in this lost of energy. An endothermic reaction would absorb energy and make the temperature rise.

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3 years ago

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Identify the species oxidized. 2 al3+(aq) + 2 fe(s) → 2 al(s) + 3 fe2+(aq)

Sliva [168]

To know the answer, compare the oxidation number of the element in the reactant and the product side. The oxidation number of Al was originally +3, then became 0 after the reaction. On the other hand, Fe was originally 0, then became +2 after the reaction. When the element is oxidized, it oxidation number increases. <em>Thus, the element oxidized is Fe.</em>

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3 years ago

Lithium is a metal.

Zina [86]

Answer:

Explanation:

lithium: lithium is very soft, silvery metal. melting point is 180.54°C and boiling point is 1,335°C. it's density is 0.534 grams per cu.cm. oxygen: oxygen is colourless , odorless , tasteless gas

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3 years ago

When methanol, CH 3 OH , is burned in the presence of oxygen gas, O 2 , a large amount of heat energy is released. For this reas

luda_lava [24]

<u>Answer:</u> The mass of methanol that must be burned is 24.34 grams

<u>Explanation:</u>

We are given:

Amount of heat produced = 581 kJ

For the given chemical equation:

$CH_3OH(g)+\frac{3}{2}O_2(g)\rightarrow CO_2(g)+2H_2O(l);\Delta H=-764kJ$

By Stoichiometry of the reaction:

When 764 kJ of heat is produced, the amount of methanol reacted is 1 mole

So, when 581 kJ of heat will be produced, the amount of methanol reacted will be = $\frac{1}{764}\times 581=0.7605mol$

To calculate mass for given number of moles, we use the equation:

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

Moles of methanol = 0.7605 moles

Molar mass of methanol = 32 g/mol

Putting values in above equation, we get:

$0.7605mol=\frac{\text{Mass of methanol}}{32g/mol}\\\\\text{Mass of methanol}=(0.7605mol\times 32g/mol)=24.34g$

Hence, the mass of methanol that must be burned is 24.34 grams

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3 years ago

10 points !! Which can happen during a physical change?

Sveta_85 [38]

I think that the answer is A because if you think about water for an example. When water turns into ice, it's still technically water, just the molecules are frozen. The water is physically changed. It could also see why you think it is B but I don't think so completely. It doesn't really make sense to me. So I'd choose A. It's definitely not C or D.

5 0

3 years ago