你會用無土栽培花卉嗎?有一種無土栽培花卉的營養(yǎng)液的溶質(zhì)質(zhì)量分?jǐn)?shù)為1.6%,它的成分有磷酸銨、硝酸鉀、硫酸銨、硝酸銨和硫酸亞鐵,且它們質(zhì)量比為:22:105:16:16:1.現(xiàn)需要配制500g的這種營養(yǎng)液,則需要水________g,500g營養(yǎng)液中鉀元素的質(zhì)量是________g.(精確到0.1g)
492.0 2.0
分析:(1)根據(jù)這種營養(yǎng)液的質(zhì)量和質(zhì)量分?jǐn)?shù),利用溶質(zhì)質(zhì)量=溶液質(zhì)量×溶質(zhì)質(zhì)量分?jǐn)?shù)可以計算出溶質(zhì)的質(zhì)量,再根據(jù)溶劑質(zhì)量=溶液質(zhì)量-溶質(zhì)質(zhì)量即可計算出需要水的質(zhì)量;
(2)由(1)可知500g溶液中溶質(zhì)質(zhì)量,根據(jù)各成分中各物質(zhì)的質(zhì)量比可以計算出硝酸鉀的質(zhì)量;最后根據(jù)硝酸鉀的化學(xué)式可以計算出其中所含鉀元素的質(zhì)量.
解答:(1)500g溶質(zhì)質(zhì)量分?jǐn)?shù)為1.6%這種營養(yǎng)液中溶質(zhì)的質(zhì)量為:500g×1.6%=8g;
則需水的質(zhì)量為:500g-8g=492.0g;
(2)500g溶質(zhì)質(zhì)量分?jǐn)?shù)為1.6%這種營養(yǎng)液中溶質(zhì)的質(zhì)量為:500g×1.6%=8g;
各成分中硝酸鉀所占有的質(zhì)量為:8g×

=5.25g;
則KNO
3中鉀元素的質(zhì)量為:5.25g×

×100%=2.0g;
故答案為:492.0;2.0.
點評:本題考查了溶質(zhì)質(zhì)量分?jǐn)?shù)的計算;在計算第二問時,要注意所有的鉀元素全部來自硝酸鉀,故計算硝酸鉀中鉀元素的質(zhì)量即為500g營養(yǎng)液中鉀元素的質(zhì)量.