Answer:
Precise but not accurate.
Explanation:
We can tell the performance of the balance is precise, because the repeated measurements give values close to one another.
However, the performance of the balance is not accurate, as the mean value of the repeated measurements (195.587) is not close to the value considered as true (in this case the standard calibration mass with a certified value of 200.002 g).
 
        
             
        
        
        
Answer:
 1.56 g of water was involved in the reaction
Explanation:
From the stoichiometric equation
2Na + 2H2O = 2NaOH + H2
NB : Mm Na= 23, Mm H2O = ( 2+16)= 18
2(23) of Na requires 2(18) of water
Hence 1.99g of Na will require 1.99×2×18/2(23) of water = 1.56 g of water
 
        
                    
             
        
        
        
<h3>
Answer:  4.25 g/ml %</h3>
Explanation:
weight/volume percentage concentration = (mass in g  ÷  volume) × 100
                                                                       =  (0.850 g ÷ 20 ml) × 100
                                                                       = 4.25 g/ml %
∴ the weight/volume percentage concentration of the sucrose solution is 4.25 g/ml %.
 
        
        
        
<span>
<span> 250g H2SO4 x 1moleH2SO4/ 98g mole H2SO4 x 4moles Oxygen/1moleH2SO4 x 1moleOxgen/16g Oxygen 
= 163.27g Oxygen 
my figures aren't exact....so it's 160g </span>
</span>
        
             
        
        
        
Answer:
Glucose 
Explanation:
It's the food plants need to complete photosynthesis.