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Alina [70]
4 years ago
10

If the unknown elements on the periodic table are "unknown" how did they end up in the periodic table in the first place? *think

ing emoji face*
Chemistry
1 answer:
mezya [45]4 years ago
8 0

Answer:

The periodic table is a marvel of organization, with each column and each row showing all ... Scientists identified the rest of them in the first half of the 20th century. ... They created in their lab a synthetic, previously unknown element. ... The Berkeley scientists did this for weeks on end, and produced a tiny amount of curium.

Explanation:

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(2) Given the following reaction:
Anika [276]

Answer: 295.46g

Explanation: please see attached file for explanation.

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3 years ago
How did worldwide infant mortality and life expectancy changed between 1900 ?
Pavel [41]
<span>Infant mortality dropped significantly - raising the average age at death. It depends on how you look at the statistics. </span>
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4 years ago
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When gaseous ammonia is passed over solid copper(Il) oxide at high temperatures, nitrogen gas is formed. 2NH3(g) + 3CuO(s)---&gt
antoniya [11.8K]

Answer:

copper(ll)oxide

Explanation:

Limit reagent is a reagent that finished thereby stopping the reaction.

2NH3(g) + 3CuO(s)---> N2(g) + 3Cu(s) + 3H20(g)

molar mass of of ammonia = 17.031 × 2  (stiochiometry mole) = 34.06 g/mol

molar mass of CuO = 79.545 × 3 = 238.635 g/mol

molar mass of Nitrogen gas =  28.0134 g/mol

34.06 g of NH3   need 238.635 of CuO to produce 28.0134 of Nitrogen gas

238.635g produce 28.0134 g

x gram of CuO  produce 26 gram of Nitrogen gas

x gram = ( 26 × 238.635 ) / 28.0134 = 221.484 g

also

34.06  g of ammonia produces 28.0134g of nitogen gas

y gram of ammonia produce 26g

y gram = (26× 34.06) / 28.0134 g = 31.61 g

but the 34 g of ammonia was used in the reaction and 31.61 reacted leaving and 2.39 g of ammonia gas

The limiting reagent therefore is copper(ll)oxide

6 0
3 years ago
How many molecules of ascorbic acid (vitamin c, c6h8o6) are in a 500 mg tablet?
Elden [556K]
1) molar mass of the C6H8O<span>6, you need to consult the atomic weight of the C, H and O atoms that are in the periodic table: C is 12; H is 1; O is 16
(12x6)+(1x8)+(16x6)= 176g/mol

</span><span>176 g = 1 mol
0,5 g =  x mol                500mg= 0,5 grams

molar mass = mass÷ moles
176 = 0,5÷ x
x= 2,84 x 10⁻³ mol

2) To find the number of molecules present in those </span>2,84 x 10⁻³ mol we need to multiple the moles by the <span>Avogadro's constant
No. of molecules = Avogadro's constant  x n° of moles
</span>No. of molecules = 6.022 x 10²³ x 2,84 x 10⁻³ <span>
= 1.71 x 10²¹ molecules of vit C. </span>







6 0
3 years ago
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anyanavicka [17]
I want to say B but I’m rusty on this topic
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