（Ⅰ）求 $f\left(x\right)$ 在 $x\in -\frac{\pi }{2},0$ 时的值域；

（Ⅱ）已知数列 $a_n=n^{2}f\left(\frac{n\pi }{2}-\frac{11\pi }{24}\right)$ $\left(n\in N^{*}\right)$ ，求 $\left\{a_n\right\}$ 的前2n项和 $S_{2n}$ ．

下列有关Fe₂（SO₄）₃溶液的叙述正确的是（　　）

    Now people are very concerned about the food problem. Steve Wilson prefers organic fruit, delivered right to the doorstep. He is willing to pay for it. If this is not possible, the 30-year-old computer technician will spend the extra money at the supermarket to buy organic food.

    “Organic product is always better,” Wilson said. “The food is free of pesticides(农药), and you are generally supporting family farms instead of large farms. And more often than not that it is locally grown and seasonal, so it is more tasty.” Wilson is one of the growing number of shoppers buying into the organic trend, and supermarkets across Britain are counting on more like him as they grow their organic food business. But how many shoppers really know what they are getting, and why are they willing to pay a higher price for organic product? Market research shows that Wilson and others who buy organic food can generally give clear reasons for their preferences—but their knowledge of organic food is far from complete. For example, small amounts of pesticides can be used on organic products. And about three quarters of organic food in Britain is not local but imported(进口)to meet growing demand. “The demand for organic food is increasing by about one third every year, so it is a very fast-growing market,” said Sue Flock, a specialist in this line of business.