Answer:
The atomic number that should be here, 57, is located at the bottom of the table in the row called the Lanthanides. Directly below the space in Row 6, in Row 7, is another empty space, which is filled by a row called the Actinides, also seen at the bottom of the chart.
Explanation:
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The fuel released 90 calories of heat.
Let suppose that water experiments an entirely <em>sensible</em> heating. Hence, the heat released by the fuel is equal to the heat <em>absorbed</em> by the water because of principle of energy conservation. The heat <em>released</em> by the fuel is expressed by the following formula:
(1)
Where:
- Mass of the sample, in grams.
- Specific heat of water, in calories per gram-degree Celsius.
- Temperature change, in degrees Celsius.
If we know that 
, 
and 
, then the heat released by the fuel is:
The fuel released 90 calories of heat.
We kindly invite to check this question on sensible heat: brainly.com/question/11325154
A wave.
Scientists now recognize that light can behave as both a particle and a wave.
Answer:
K₂Cr₂O₇(s) ⇒ 2 K⁺(aq) + Cr₂O₇²⁻(aq)
Explanation:
Potassium dichromate (K₂Cr₂O₇) is a strong electrolyte, that is, when dissolved in water (the medium), it dissociates in cation potassium (K⁺) and anion dichromate (Cr₂O₇²⁻). The balanced dissociation equation is:
K₂Cr₂O₇(s) ⇒ 2 K⁺(aq) + Cr₂O₇²⁻(aq)
