Just divide!
60 seconds = 1 min
60 mins = 1 hour
1987 seconds divided by 60 seconds = 33.11 minutes
Your answer would be 33 minutes and 11 seconds
Chromium (Cr): 2, 8, 8, 6
Copper (Cu): 2, 8, 8, 11
Chromium+2 (Cr+2): 2, 8, 8, 4 (if the ion retains a positive charge then the amount of electrons will decrease)
Copper+2 (Cu+2): 2, 8, 8, 9
Manganese+2 (Mn+2): 2, 8, 8, 5
Rf values may vary. Rf values vary depending on the material and solvent. The solvent that is used will alter the Rf value.
Rf values are typically higher for low polarity chemicals compared to higher polarity ones. Generally speaking, as polarity of a compound increases, so does its adsorptivity (i.e. the more polar the compound then the stronger it binds to the adsorbent). Solvents get more eluting as they become more polar.
The greater the compound's polarity, the more readily it will bind to the adsorbent, the closer it will come to the baseline, and the lower its Rf value. Many scientists use normal-phase flash chromatography with dichloromethane and methanol as the mobile phase to purify polar organic molecules. Due to methanol's high polarity and protic chemistry, it can frequently be difficult to optimize this solvent system.
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Answer:
The correct order of the elements, taking into account their ionic radius from highest to lowest, is:
<em>a) Cl⁻¹ > F⁻¹ > Na⁺¹ > Mg⁺²</em>
<em>b) S⁻² > O⁻² > Li⁺¹ > Be⁺²</em>
<em>c) S⁻² > Cl⁻¹ > K⁺¹ > Na⁺¹</em>
Explanation:
In ions the ionic radius is determined by the amount of electrons an element gains or loses to become an ion. The more negative an ion is, the greater its ionic radius.
As a rule, anions (negative charge) have a larger ionic radius than cations (positive charge), because the loss of electrons means a contraction of the ionic radius, while the gain of electrons means a greater radius.
To determine which ionic radius is greater in anions or cations with the same charge, it must be considered that in the periodic table the ionic radius increases from top to bottom and from right to left.
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