Which of the following measurements is expressed to three significant figures?
C. 5.60 km
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The number of grams in 1.70 moles of Ca(NO₃)₂ is 384.2 grams
<h3>How to determine the mass of Ca(NO₃)₂</h3>
The mole of a substance is related to it's mass and molar mass according to the following equation:
Mole = mass / molar mass
With the above formula, we can determine the mass of Ca(NO₃)₂ as illustrated below:
- Mole of Ca(NO₃)₂ = 1.70 moles
- Molar mass of Ca(NO₃)₂ = 40 + 3[14 + (16 × 3)] = 40 + 3[14 + 48] = 40 + 3(62) = 40 + 186 = 226 g/mol
- Mass of Ca(NO₃)₂ = ?
Mole = mass / molar mass
1.70 = Mass of Ca(NO₃)₂ / 226
Cross multiply
Mass of Ca(NO₃)₂ = 1.70 × 226
Mass of Ca(NO₃)₂ = 384.2 grams
Thus, the mass of 1.70 moles of Ca(NO₃)₂ is 384.2 grams
Learn more about mole:
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Answer:
The pH is equal to 4.41
Explanation:
Since HClO is a weak acid, its dissociation in aqueous medium is:
HClO ⇄ ClO- + H+
start: 0.05 0 0
change -x +x +x
balance 0.05-x x x
As it is a weak acid it dissociates very little, in its ClO- and H + ions, so the change is negative, where x is a degree of dissociation.
the acidity constant when equilibrium is reached is equal to:
![Ka=\frac{[ClO-]*[H+]}{[HClO]}=\frac{x*x}{0.05-x}=3x10^{-8}](https://tex.z-dn.net/?f=Ka%3D%5Cfrac%7B%5BClO-%5D%2A%5BH%2B%5D%7D%7B%5BHClO%5D%7D%3D%5Cfrac%7Bx%2Ax%7D%7B0.05-x%7D%3D3x10%5E%7B-8%7D)
The 0.05-x fraction can be approximated to 0.05, because the ionized fraction (x) is very small, therefore we have:

clearing the x and calculating its value we have:
![x=3.87x10^{-5}=[H+]=[ClO-]](https://tex.z-dn.net/?f=x%3D3.87x10%5E%7B-5%7D%3D%5BH%2B%5D%3D%5BClO-%5D)
the pH can be calculated by:
![pH=-log[H+]=-log[3.87x10^{-5}]=4.41](https://tex.z-dn.net/?f=pH%3D-log%5BH%2B%5D%3D-log%5B3.87x10%5E%7B-5%7D%5D%3D4.41)