Calcium oxide reacts with water in a combination reaction to produce calcium hydroxide. Ca) + H2O --> Ca(OH)2 In a particular
2 answers:
Answer:
Percent yield = 92.5%
Explanation:
The question asks for the percent yield which can be defined as:
Where the actual yield is <em>how much product was obtained</em>, in this case 6.11 g of Ca(OH)₂, and the theoretical yield is <em>how much product could be obtained with the given reactants theoretically</em>, that is if the reaction would work perfectly. So we need to calculate first the theoretical yield.
1. First lets write the chemical equation reaction correctly and check that it is balanced:
CaO + H₂O → Ca(OH)₂
2. Calculate the amount of product Ca(OH)₂ that can be obtained with the given reactants (theoretical yield), which are 5.00g of CaO and excess of water. So the amount of CaO will determined how much Ca(OH)₂ we can obtained.
For this we'll use the molar ratio between CaO and Ca(OH)₂ which we see it is 1:1. For every mol of CaO we'll obtain a mol of Ca(OH)₂. So lets convert the 5.00 g of CaO to moles:
Molar Mass of CaO: 40.078 + 15.999 = 56.077 g/mol
moles of CaO = 5.00 g / 56.077 g/mol = 0.08916 moles
As we said before from the molar ratio moles of Ca(OH)₂ = moles of CaO
So the moles of Ca(OH)₂ that can be obtained are 56.077 g/mol
We need to convert this value to grams:
Molar Mass of Ca(OH)₂ = 40.078 + (15.999 + 1.008)*2 = 74.092 g/mol
Theoretical yield of Ca(OH)₂ = 0.08916 moles x 74.092 g/mol = 6.606 g
3. Calculate the percent yield:
Percent yield = (6.11 g / 6.606g) x 100 = 92.5 %
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Answer: A. -396 kJ
Explanation:
The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements, with all substances in their standard states.
Reversing the reaction, changes the sign of
On multiplying the reaction by 2, enthalpy gets multiplied by 2:
Thus the enthalpy change for the reaction is -396 kJ.
Explanation:
<em><u>SMARTPHONE OWNERSHIP IS GROWING RAPIDLY AROUND THE WORLD, BUT NOT ALWAYS THE SAME.</u></em>
In emerging economies, the use of technology is still more common among the young and the educated
A farmer takes a selfie with a smartphone at a rally in Jaipur, India. (Vishal Bhatnagar/AFP/Getty Images)
A farmer takes a selfie with a smartphone at a rally in Jaipur, India. (Vishal Bhatnagar/AFP/Getty Images)
The chart shows that smartphone ownership in advanced economies is higher than in emerging economies.
Mobile technology has spread rapidly around the world. Today, it is estimated that more than 5 billion people have mobile devices, and more than half of these connections are smartphones. But growth in mobile technology so far has been unequal, either nationwide or within it. People in advanced economies are more likely to have mobile phones - smartphones in particular - and more likely to use the internet and social media than people in emerging economies. For example, a median of 76% across the 18 advanced economies surveyed have a smartphone, compared to a median of only 45% in emerging economies.
Smartphone ownership can vary by country, and even across developed economies. While about nine in ten or more South Koreans, Israelis and the Netherlands own a smartphone, the ownership rate is closer to six in ten in other developed countries such as Poland, Russia and Greece. In emerging economies as well, smartphone ownership rates vary significantly, from a high of 60% in South Africa and Brazil to just around four in ten in Indonesia, Kenya and Nigeria. Among the countries surveyed, ownership was lowest in India, where only 24% reported having a smartphone.
