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bezimeni [28]
3 years ago
6

Mendeleev placed thallium (Tl) in the same group as lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). Ho

wever, the modern periodic table doesn’t place thallium in this group. Use the periodic table to find the properties of thallium. Explain why Mendeleev might have grouped thallium in the same group as lithium and sodium. Also explain how thallium is different from the other five elements.
Chemistry
1 answer:
EastWind [94]3 years ago
4 0

Answer:

When observing how thallium reacts with the air of the earth's atmosphere, its hardness or resistance resembled sodium, it was not investigated further to classify it correctly

Explanation:

Now it is known that they contain different numbers of valence electrons and that thallium is a heavy metal like lead and that they have similar characteristics except for their melting point where thallium is higher.

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The weak acid HZ has a Ka of 2.55x10⁻⁴.(a) Calculate the pH of 0.075 M HZ.
Dima020 [189]

<u>2.37</u> is the pH of 0.075 M HZ.

<h3>What is pH?</h3>

The term pH, which originally stood for "potential of hydrogen" (or "power of hydrogen"), is used in chemistry to describe how acidic or basic an aqueous solution is. Lower pH values are summarized for acidic solutions (solutions with higher H+ ion concentrations) than for basic or alkaline solutions.

The pH scale is inversely indicates to the concentration of hydrogen ions in the solution and is logarithmic.

⇒pH = -log(a_{H+})

Acidic solutions are those with a pH below 7, and basic solutions are those with a pH above 7, at a temperature of 25 °C (77 °F). At this temperature, solutions with a pH of 7 are neutral (e.g. pure water). The pH neutrality relies on temperature, falling below 7 if the temperature rises above 25 °C.

Learn more about pH

brainly.com/question/12609985

#SPJ4

4 0
2 years ago
What is the theoretical yield of methanol (CH3OH) when 12.0 grams of H2 is mixed with 74.5 grams of CO? CO + 2H2 CH3OH
AlladinOne [14]
1) We need to convert 12.0 g of H2 into moles of H2, and <span> 74.5 grams of CO into moles of CO
</span><span>Molar mass of H2:    M(H2) = 2*1.0= 2.0 g/mol
Molar mass of CO:   M(CO) = 12.0 +16.0 = 28.0 g/mol

</span>12.0 g  H2 * 1 mol/2.0 g = 6.0 mol H2
74.5 g CO * 1 mol/28.0 g = 2.66 mol CO

<span>2) Now we can use reaction to find out what substance will react completely, and what will be leftover. 

                                  CO       +         2H2   ------->      CH3OH  
                                 1 mol              2 mol
given                        2.66 mol          6 mol (excess)

How much
we need  CO?           3 mol              6 mol

We see that H2 will be leftover, because for 6 moles H2  we need 3 moles CO, but we have only 2.66 mol  CO.
So, CO will react completely, and we are going to use CO to find  the mass of CH3OH.

3)                              </span>CO       +         2H2   ------->      CH3OH  
                                 1 mol                                        1 mol
                                2.66 mol                                    2.66 mol

4) We have 2.66 mol CH3OH
Molar mass CH3OH : M(CH3OH) = 12.0 +  4*1.0 + 16.0 = 32.0 g/mol

2.66 mol CH3OH * 32.0 g CH3OH/ 1 mol CH3OH =  85.12 g CH3OH
<span>
Answer is </span>D) 85.12 grams.
3 0
3 years ago
g The reaction; 4 Ag(s) + O2(g) ----&gt; 2 Ag2O(s), is exothermic. Which statement about the reaction is correct? (A) It is spon
melomori [17]

Answer:

The correct answer is B. It is spontaneous only at low temperatures.

Explanation:

In thermodynamics, the Gibbs free energy is a thermodynamic potential that can be used to calculate the maximum of reversible work that may be performed by a thermodynamic system at a constant temperature and pressure.

The spontaneity of a reaction is given by the equation:

ΔG = ΔH - TΔS

where:

ΔH: enthalpy variation

T: absolute temperature

ΔS: entropy variation

As the reaction is exothermic, ΔH<0

As the reaction order increases (the reagents are solid and gas and their product is solid), ΔS<0

Therefore, the reaction will be spontaneous when ΔG is negative.

ΔG = ΔH - TΔS

That is, the entropy term must be smaller than the enthalpy term.

Hence, the reaction will be spontaneous only at low temperatures.

4 0
3 years ago
Suppose an adult is encased in a thermally insulating barrier so that all the heat evolved by metabolism of foodstuffs is retain
mihalych1998 [28]
Given:
Q = 9.4 kJ/(kg-h), the heat production rate
c = 4.18 J/(g-K), the heat capacity
t = 2.5 h, amount of time

Note that
c = 4.18 J/(g-K) = 4180 J/(kg-K) = 4.18 kJ/kg-K)

Consider 1 kg of mass.
Then
Qt = cΔT
where ΔT is the increase in temperature (°K)
(1 kg)*(9.4 kJ/(kg-h))*(2.5 h) = (1 kg)*(4.18 kJ/(kg-K))*(ΔT K)
23.5 = 4.18 ΔT
ΔT = 23.5/4.18 = 5.622 K = 5.622 °C

Answer: 5.62 K (or 5.62 °C)

7 0
3 years ago
What is/are converted into carbon dioxide , water, and energy in aerobic respiration
Lana71 [14]

Cellular respiration involves breakdown of glucose into carbon dioxide and water in presence of oxygen, releasing energy. ... ATP molecule is converted into ADP molecule, whenever energy is needed for any metabolic reaction or activity. The energy stored in it is released to be used in metabolic reaction.

Hope this helps! So sorry if I'm wrong

3 0
3 years ago
Read 2 more answers
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