There are 3 significant figures. Significant numbers are the numbers that build up your total number. 1-9 always count, 0 only counts if it’s after another number. For example: 0,901 has 3 significant numbers as does 0,910. 9,10 also has 3. 0,09 has just 1.
Answer:
340 grams Ca₃P₂ (2 sig. figs.)
Explanation:
3Ca + 2P => Ca₃P₂
5.6 mole + excess => ? grams
Convert the 'known' to a coefficient of 1 by dividing all coefficients by 3.
=> Ca + 2/3P => 1/3Ca₃P₂
From the above, 1 mole of Ca => 1/3 mole Ca₃P₂
∴ 5.6 mole Ca in an excess of P => 1/3(5.6 mole) Ca₃P₂
=> 1.8666 mol Ca₃P₂ (calculator answer) ≅ 1.9 mol Ca₃P₂
=> 1.9 mole x 182 g Ca₃P₂/mol Ca₃P₂ = 339.73333 grams Ca₃P₂
≅ 340 grams Ca₃P₂ (2 sig. figs.)
the reaction is HF + NaOH which leads to NaF
Equal volumes of equal concentrations of strong acid and strong base are mixed. Because the volumes and molarities are equal, the number of mole NaOH and HCl are equal.
From reaction
HCl + NaOH ---> NaCl +H2O
we can see that if number of moles HCl and NaOH are equal, they will react completely, and no acid or base is going to be in solution anymore.
So, pH=7.
