4) would be your correct answer
I believe the answer is C because the first two are mechanical hazards and C mentions plug which is electrical.
Answer:
The pH value of the mixture will be 7.00
Explanation:
Mono and disodium hydrogen phosphate mixture act as a buffer to maintain pH value around 7. Henderson–Hasselbalch equation is used to determine the pH value of a buffer mixture, which is mathematically expressed as,
![pH=pK_{a} + log(\frac{[Base]}{[Acid]})](https://tex.z-dn.net/?f=pH%3DpK_%7Ba%7D%20%2B%20log%28%5Cfrac%7B%5BBase%5D%7D%7B%5BAcid%5D%7D%29)
According to the given conditions, the equation will become as follow
![pH=pK_{a} + log(\frac{[Na_{2}HPO_{4} ]}{[NaH_{2}PO_{4}]})](https://tex.z-dn.net/?f=pH%3DpK_%7Ba%7D%20%2B%20log%28%5Cfrac%7B%5BNa_%7B2%7DHPO_%7B4%7D%20%5D%7D%7B%5BNaH_%7B2%7DPO_%7B4%7D%5D%7D%29)
The base and acid are assigned by observing the pKa values of both the compounds; smaller value means more acidic. NaH₂PO₄ has a pKa value of 6.86, while Na₂HPO₄ has a pKa value of 12.32 (not given, but it's a constant). Another more easy way is to the count the acidic hydrogen in the molecular formula; the compound with more acidic hydrogens will be assigned acidic and vice versa.
Placing all the given data we obtain,


Answer: The correct option is C ( is very hard and burns cleanly).
Explanation:
COAL is a form of rock that is made up of mostly carbon amongst other elements which includes sulphur, nitrogen, hydrogen and oxygen. There are different types of coal which include:
--> anthracite ( 90% carbon)
--> bituminous coal ( 70-90% carbon)
--> lignite ( 60- 70% carbon) and
--> peat (60 % carbon).
Anthracite is the type of coal that contains the highest carbon content ( 90% carbon). This makes it very hard and is often a times referred to as HARD COAL. Anthracite is a higher quality coal for domestic and open fire heating. This is because it contains less impurities than other type of coal and thereby making it to BURN CLEANLY avoiding atmospheric pollution.